NAK new drivers without proper power management?

NAK new drivers without proper power management?

[Nigel Cunningham]

Hi.

I don't think this is already done (feel free to correct me if I'm
wrong)..

Can we start to NAK new drivers that don't have proper power management
implemented? There really is no excuse for writing a new driver and not
putting .suspend and .resume methods in anymore, is there?

Regards,

Nigel-getting-sick-of-drivers-without-pm-support Cunningham

Re: NAK new drivers without proper power management?

[Arjan van de Ven]

On Sat, 2007-02-10 at 08:57 +1100, Nigel Cunningham wrote:
> Hi.
> 
> I don't think this is already done (feel free to correct me if I'm
> wrong)..
> 
> Can we start to NAK new drivers that don't have proper power management
> implemented? There really is no excuse for writing a new driver and not
> putting .suspend and .resume methods in anymore, is there?


to a large degree, a device driver that doesn't suspend is better than
no device driver at all, right?
now.. if you want to make the core warn about it, that's very fair

Re: NAK new drivers without proper power management?

[Nigel Cunningham]

Hi.

On Fri, 2007-02-09 at 23:17 +0100, Arjan van de Ven wrote:
> On Sat, 2007-02-10 at 08:57 +1100, Nigel Cunningham wrote:
> > Hi.
> > 
> > I don't think this is already done (feel free to correct me if I'm
> > wrong)..
> > 
> > Can we start to NAK new drivers that don't have proper power management
> > implemented? There really is no excuse for writing a new driver and not
> > putting .suspend and .resume methods in anymore, is there?
> 
> 
> to a large degree, a device driver that doesn't suspend is better than
> no device driver at all, right?

I'm not sure it is. It only makes more work for everyone else: We have
to help people figure out what causes their computer to fail to resume
(which can take quite a while), then get them them complain to driver
author, and the driver author has to submit patches to fix it.

All of this is avoided if they'll just do it right in the first place.

> now.. if you want to make the core warn about it, that's very fair

That's probably a good idea too, since I'm only suggesting this for new
drivers.

Regards,

Nigel

Re: NAK new drivers without proper power management?

[Rafael J. Wysocki]

On Friday, 9 February 2007 23:26, Nigel Cunningham wrote:
> Hi.
> 
> On Fri, 2007-02-09 at 23:17 +0100, Arjan van de Ven wrote:
> > On Sat, 2007-02-10 at 08:57 +1100, Nigel Cunningham wrote:
> > > Hi.
> > > 
> > > I don't think this is already done (feel free to correct me if I'm
> > > wrong)..
> > > 
> > > Can we start to NAK new drivers that don't have proper power management
> > > implemented? There really is no excuse for writing a new driver and not
> > > putting .suspend and .resume methods in anymore, is there?
> > 
> > 
> > to a large degree, a device driver that doesn't suspend is better than
> > no device driver at all, right?
> 
> I'm not sure it is. It only makes more work for everyone else: We have
> to help people figure out what causes their computer to fail to resume
> (which can take quite a while), then get them them complain to driver
> author, and the driver author has to submit patches to fix it.
> 
> All of this is avoided if they'll just do it right in the first place.
> 
> > now.. if you want to make the core warn about it, that's very fair
> 
> That's probably a good idea too, since I'm only suggesting this for new
> drivers.

I think if CONFIG_PM_DEBUG is set, the core should warn about drivers not
having .suspend or .resume routines.

Greetings,
Rafael


-- 
If you don't have the time to read,
you don't have the time or the tools to write.
		- Stephen King

Re: NAK new drivers without proper power management?

[Rafael J. Wysocki]

On Friday, 9 February 2007 23:26, Nigel Cunningham wrote:
> Hi.
> 
> On Fri, 2007-02-09 at 23:17 +0100, Arjan van de Ven wrote:
> > On Sat, 2007-02-10 at 08:57 +1100, Nigel Cunningham wrote:
> > > Hi.
> > > 
> > > I don't think this is already done (feel free to correct me if I'm
> > > wrong)..
> > > 
> > > Can we start to NAK new drivers that don't have proper power management
> > > implemented? There really is no excuse for writing a new driver and not
> > > putting .suspend and .resume methods in anymore, is there?
> > 
> > 
> > to a large degree, a device driver that doesn't suspend is better than
> > no device driver at all, right?
> 
> I'm not sure it is. It only makes more work for everyone else: We have
> to help people figure out what causes their computer to fail to resume
> (which can take quite a while), then get them them complain to driver
> author, and the driver author has to submit patches to fix it.
> 
> All of this is avoided if they'll just do it right in the first place.
> 
> > now.. if you want to make the core warn about it, that's very fair
> 
> That's probably a good idea too, since I'm only suggesting this for new
> drivers.

I think if CONFIG_PM_DEBUG is set, the core should warn about drivers not
having .suspend or .resume routines.

Greetings,
Rafael


-- 
If you don't have the time to read,
you don't have the time or the tools to write.
		- Stephen King

Re: NAK new drivers without proper power management?

[Nigel Cunningham]

Hi.

On Fri, 2007-02-09 at 23:44 +0100, Rafael J. Wysocki wrote:
> On Friday, 9 February 2007 23:26, Nigel Cunningham wrote:
> > Hi.
> > 
> > On Fri, 2007-02-09 at 23:17 +0100, Arjan van de Ven wrote:
> > > On Sat, 2007-02-10 at 08:57 +1100, Nigel Cunningham wrote:
> > > > Hi.
> > > > 
> > > > I don't think this is already done (feel free to correct me if I'm
> > > > wrong)..
> > > > 
> > > > Can we start to NAK new drivers that don't have proper power management
> > > > implemented? There really is no excuse for writing a new driver and not
> > > > putting .suspend and .resume methods in anymore, is there?
> > > 
> > > 
> > > to a large degree, a device driver that doesn't suspend is better than
> > > no device driver at all, right?
> > 
> > I'm not sure it is. It only makes more work for everyone else: We have
> > to help people figure out what causes their computer to fail to resume
> > (which can take quite a while), then get them them complain to driver
> > author, and the driver author has to submit patches to fix it.
> > 
> > All of this is avoided if they'll just do it right in the first place.
> > 
> > > now.. if you want to make the core warn about it, that's very fair
> > 
> > That's probably a good idea too, since I'm only suggesting this for new
> > drivers.
> 
> I think if CONFIG_PM_DEBUG is set, the core should warn about drivers not
> having .suspend or .resume routines.

The only problem with that is, not everyone turns on CONFIG_PM_DEBUG.
CONFIG_PM instead?

Regards,

Nigel

Re: NAK new drivers without proper power management?

[Nigel Cunningham]

Hi.

On Fri, 2007-02-09 at 23:44 +0100, Rafael J. Wysocki wrote:
> On Friday, 9 February 2007 23:26, Nigel Cunningham wrote:
> > Hi.
> > 
> > On Fri, 2007-02-09 at 23:17 +0100, Arjan van de Ven wrote:
> > > On Sat, 2007-02-10 at 08:57 +1100, Nigel Cunningham wrote:
> > > > Hi.
> > > > 
> > > > I don't think this is already done (feel free to correct me if I'm
> > > > wrong)..
> > > > 
> > > > Can we start to NAK new drivers that don't have proper power management
> > > > implemented? There really is no excuse for writing a new driver and not
> > > > putting .suspend and .resume methods in anymore, is there?
> > > 
> > > 
> > > to a large degree, a device driver that doesn't suspend is better than
> > > no device driver at all, right?
> > 
> > I'm not sure it is. It only makes more work for everyone else: We have
> > to help people figure out what causes their computer to fail to resume
> > (which can take quite a while), then get them them complain to driver
> > author, and the driver author has to submit patches to fix it.
> > 
> > All of this is avoided if they'll just do it right in the first place.
> > 
> > > now.. if you want to make the core warn about it, that's very fair
> > 
> > That's probably a good idea too, since I'm only suggesting this for new
> > drivers.
> 
> I think if CONFIG_PM_DEBUG is set, the core should warn about drivers not
> having .suspend or .resume routines.

The only problem with that is, not everyone turns on CONFIG_PM_DEBUG.
CONFIG_PM instead?

Regards,

Nigel

Re: NAK new drivers without proper power management?

[Rafael J. Wysocki]

Hi,

On Friday, 9 February 2007 23:51, Nigel Cunningham wrote:
> Hi.
> 
> On Fri, 2007-02-09 at 23:44 +0100, Rafael J. Wysocki wrote:
> > On Friday, 9 February 2007 23:26, Nigel Cunningham wrote:
> > > Hi.
> > > 
> > > On Fri, 2007-02-09 at 23:17 +0100, Arjan van de Ven wrote:
> > > > On Sat, 2007-02-10 at 08:57 +1100, Nigel Cunningham wrote:
> > > > > Hi.
> > > > > 
> > > > > I don't think this is already done (feel free to correct me if I'm
> > > > > wrong)..
> > > > > 
> > > > > Can we start to NAK new drivers that don't have proper power management
> > > > > implemented? There really is no excuse for writing a new driver and not
> > > > > putting .suspend and .resume methods in anymore, is there?
> > > > 
> > > > 
> > > > to a large degree, a device driver that doesn't suspend is better than
> > > > no device driver at all, right?
> > > 
> > > I'm not sure it is. It only makes more work for everyone else: We have
> > > to help people figure out what causes their computer to fail to resume
> > > (which can take quite a while), then get them them complain to driver
> > > author, and the driver author has to submit patches to fix it.
> > > 
> > > All of this is avoided if they'll just do it right in the first place.
> > > 
> > > > now.. if you want to make the core warn about it, that's very fair
> > > 
> > > That's probably a good idea too, since I'm only suggesting this for new
> > > drivers.
> > 
> > I think if CONFIG_PM_DEBUG is set, the core should warn about drivers not
> > having .suspend or .resume routines.
> 
> The only problem with that is, not everyone turns on CONFIG_PM_DEBUG.
> CONFIG_PM instead?

Well, I can imagine a driver that doesn't need a .suspend routine, for example,
and I don't think we should make the kernel always complain about that.

I think if someone doesn't set CONFIG_PM_DEBUG, we can ask him to set it
and report back.

Greetings,
Rafael

Re: NAK new drivers without proper power management?

[Rafael J. Wysocki]

Hi,

On Friday, 9 February 2007 23:51, Nigel Cunningham wrote:
> Hi.
> 
> On Fri, 2007-02-09 at 23:44 +0100, Rafael J. Wysocki wrote:
> > On Friday, 9 February 2007 23:26, Nigel Cunningham wrote:
> > > Hi.
> > > 
> > > On Fri, 2007-02-09 at 23:17 +0100, Arjan van de Ven wrote:
> > > > On Sat, 2007-02-10 at 08:57 +1100, Nigel Cunningham wrote:
> > > > > Hi.
> > > > > 
> > > > > I don't think this is already done (feel free to correct me if I'm
> > > > > wrong)..
> > > > > 
> > > > > Can we start to NAK new drivers that don't have proper power management
> > > > > implemented? There really is no excuse for writing a new driver and not
> > > > > putting .suspend and .resume methods in anymore, is there?
> > > > 
> > > > 
> > > > to a large degree, a device driver that doesn't suspend is better than
> > > > no device driver at all, right?
> > > 
> > > I'm not sure it is. It only makes more work for everyone else: We have
> > > to help people figure out what causes their computer to fail to resume
> > > (which can take quite a while), then get them them complain to driver
> > > author, and the driver author has to submit patches to fix it.
> > > 
> > > All of this is avoided if they'll just do it right in the first place.
> > > 
> > > > now.. if you want to make the core warn about it, that's very fair
> > > 
> > > That's probably a good idea too, since I'm only suggesting this for new
> > > drivers.
> > 
> > I think if CONFIG_PM_DEBUG is set, the core should warn about drivers not
> > having .suspend or .resume routines.
> 
> The only problem with that is, not everyone turns on CONFIG_PM_DEBUG.
> CONFIG_PM instead?

Well, I can imagine a driver that doesn't need a .suspend routine, for example,
and I don't think we should make the kernel always complain about that.

I think if someone doesn't set CONFIG_PM_DEBUG, we can ask him to set it
and report back.

Greetings,
Rafael

Re: NAK new drivers without proper power management?

[Nigel Cunningham]

Hi.

On Sat, 2007-02-10 at 00:12 +0100, Rafael J. Wysocki wrote:
> > > I think if CONFIG_PM_DEBUG is set, the core should warn about drivers not
> > > having .suspend or .resume routines.
> > 
> > The only problem with that is, not everyone turns on CONFIG_PM_DEBUG.
> > CONFIG_PM instead?
> 
> Well, I can imagine a driver that doesn't need a .suspend routine, for example,
> and I don't think we should make the kernel always complain about that.

How about...

#ifdef CONFIG_PM_PARANOIA
static int empty_suspend_routine(struct device *dev, pm_message_t state)
{
	return 0;
}
#define empty_suspend empty_suspend_routine
#else
#define empty_suspend NULL
#endif

...

	.suspend = empty_suspend;
...


Then CONFIG_PM_PARANOIA can be enabled by default for now, and when we
eventually device it's not needed anymore, someone can submit a patch
replacing either turning off the CONFIG by default or removing the whole
mechanism.

> I think if someone doesn't set CONFIG_PM_DEBUG, we can ask him to set it
> and report back.

We can, but the whole point to the suggestion was to make your life and
mine easier, as well as those of our users.

Making it dependent on CONFIG_PM instead achieves that by:
- Saving you, I and distro people from having to tell their users to
enable the option (and how to)
- Saving the users the problem of going through all the steps, making
mistakes, potentially ending up with unbootable systems because they
make mistakes and so on.

This way, they just need to look in dmesg.

Regards,

Nigel

Re: NAK new drivers without proper power management?

[Nigel Cunningham]

Hi.

On Sat, 2007-02-10 at 00:12 +0100, Rafael J. Wysocki wrote:
> > > I think if CONFIG_PM_DEBUG is set, the core should warn about drivers not
> > > having .suspend or .resume routines.
> > 
> > The only problem with that is, not everyone turns on CONFIG_PM_DEBUG.
> > CONFIG_PM instead?
> 
> Well, I can imagine a driver that doesn't need a .suspend routine, for example,
> and I don't think we should make the kernel always complain about that.

How about...

#ifdef CONFIG_PM_PARANOIA
static int empty_suspend_routine(struct device *dev, pm_message_t state)
{
	return 0;
}
#define empty_suspend empty_suspend_routine
#else
#define empty_suspend NULL
#endif

...

	.suspend = empty_suspend;
...


Then CONFIG_PM_PARANOIA can be enabled by default for now, and when we
eventually device it's not needed anymore, someone can submit a patch
replacing either turning off the CONFIG by default or removing the whole
mechanism.

> I think if someone doesn't set CONFIG_PM_DEBUG, we can ask him to set it
> and report back.

We can, but the whole point to the suggestion was to make your life and
mine easier, as well as those of our users.

Making it dependent on CONFIG_PM instead achieves that by:
- Saving you, I and distro people from having to tell their users to
enable the option (and how to)
- Saving the users the problem of going through all the steps, making
mistakes, potentially ending up with unbootable systems because they
make mistakes and so on.

This way, they just need to look in dmesg.

Regards,

Nigel

Re: NAK new drivers without proper power management?

[Rafael J. Wysocki]

On Saturday, 10 February 2007 00:28, Nigel Cunningham wrote:
> Hi.
> 
> On Sat, 2007-02-10 at 00:12 +0100, Rafael J. Wysocki wrote:
> > > > I think if CONFIG_PM_DEBUG is set, the core should warn about drivers not
> > > > having .suspend or .resume routines.
> > > 
> > > The only problem with that is, not everyone turns on CONFIG_PM_DEBUG.
> > > CONFIG_PM instead?
> > 
> > Well, I can imagine a driver that doesn't need a .suspend routine, for example,
> > and I don't think we should make the kernel always complain about that.
> 
> How about...
> 
> #ifdef CONFIG_PM_PARANOIA
> static int empty_suspend_routine(struct device *dev, pm_message_t state)
> {
> 	return 0;
> }
> #define empty_suspend empty_suspend_routine
> #else
> #define empty_suspend NULL
> #endif
> 
> ...
> 
> 	.suspend = empty_suspend;
> ...
> 
> 
> Then CONFIG_PM_PARANOIA can be enabled by default for now, and when we
> eventually device it's not needed anymore, someone can submit a patch
> replacing either turning off the CONFIG by default or removing the whole
> mechanism.

I think that would be tempting people to abuse it, for example by defining or
undefining things just to quieten the warning.

In my opinion the only way to make the warning go away should be to define
a non-NULL .suspend (.resume) routine and that's why I don't think the warning
should be mandatory.

> > I think if someone doesn't set CONFIG_PM_DEBUG, we can ask him to set it
> > and report back.
> 
> We can, but the whole point to the suggestion was to make your life and
> mine easier, as well as those of our users.
> 
> Making it dependent on CONFIG_PM instead achieves that by:
> - Saving you, I and distro people from having to tell their users to
> enable the option (and how to)

I think the distro people can patch their kernels to fit their needs.

> - Saving the users the problem of going through all the steps, making
> mistakes, potentially ending up with unbootable systems because they
> make mistakes and so on.
> 
> This way, they just need to look in dmesg.

Well, IMO, if someone doesn't know how to compile and install the kernel,
he'll be using a distro kernel anyway and then see above.  Otherwise we can
safely ask him to turn on whatever debugging options we need.

Greetings,
Rafael


-- 
If you don't have the time to read,
you don't have the time or the tools to write.
		- Stephen King

Re: NAK new drivers without proper power management?

[Rafael J. Wysocki]

On Saturday, 10 February 2007 00:28, Nigel Cunningham wrote:
> Hi.
> 
> On Sat, 2007-02-10 at 00:12 +0100, Rafael J. Wysocki wrote:
> > > > I think if CONFIG_PM_DEBUG is set, the core should warn about drivers not
> > > > having .suspend or .resume routines.
> > > 
> > > The only problem with that is, not everyone turns on CONFIG_PM_DEBUG.
> > > CONFIG_PM instead?
> > 
> > Well, I can imagine a driver that doesn't need a .suspend routine, for example,
> > and I don't think we should make the kernel always complain about that.
> 
> How about...
> 
> #ifdef CONFIG_PM_PARANOIA
> static int empty_suspend_routine(struct device *dev, pm_message_t state)
> {
> 	return 0;
> }
> #define empty_suspend empty_suspend_routine
> #else
> #define empty_suspend NULL
> #endif
> 
> ...
> 
> 	.suspend = empty_suspend;
> ...
> 
> 
> Then CONFIG_PM_PARANOIA can be enabled by default for now, and when we
> eventually device it's not needed anymore, someone can submit a patch
> replacing either turning off the CONFIG by default or removing the whole
> mechanism.

I think that would be tempting people to abuse it, for example by defining or
undefining things just to quieten the warning.

In my opinion the only way to make the warning go away should be to define
a non-NULL .suspend (.resume) routine and that's why I don't think the warning
should be mandatory.

> > I think if someone doesn't set CONFIG_PM_DEBUG, we can ask him to set it
> > and report back.
> 
> We can, but the whole point to the suggestion was to make your life and
> mine easier, as well as those of our users.
> 
> Making it dependent on CONFIG_PM instead achieves that by:
> - Saving you, I and distro people from having to tell their users to
> enable the option (and how to)

I think the distro people can patch their kernels to fit their needs.

> - Saving the users the problem of going through all the steps, making
> mistakes, potentially ending up with unbootable systems because they
> make mistakes and so on.
> 
> This way, they just need to look in dmesg.

Well, IMO, if someone doesn't know how to compile and install the kernel,
he'll be using a distro kernel anyway and then see above.  Otherwise we can
safely ask him to turn on whatever debugging options we need.

Greetings,
Rafael


-- 
If you don't have the time to read,
you don't have the time or the tools to write.
		- Stephen King

Re: NAK new drivers without proper power management?

[Jeff Garzik]

Nigel Cunningham wrote:
> Hi.
> 
> On Fri, 2007-02-09 at 23:17 +0100, Arjan van de Ven wrote:
>> On Sat, 2007-02-10 at 08:57 +1100, Nigel Cunningham wrote:
>>> Hi.
>>>
>>> I don't think this is already done (feel free to correct me if I'm
>>> wrong)..
>>>
>>> Can we start to NAK new drivers that don't have proper power management
>>> implemented? There really is no excuse for writing a new driver and not
>>> putting .suspend and .resume methods in anymore, is there?
>>
>> to a large degree, a device driver that doesn't suspend is better than
>> no device driver at all, right?
> 
> I'm not sure it is. It only makes more work for everyone else: We have
> to help people figure out what causes their computer to fail to resume
> (which can take quite a while), then get them them complain to driver
> author, and the driver author has to submit patches to fix it.
> 
> All of this is avoided if they'll just do it right in the first place.

A lot of a lot of things could have been avoided, if they just did it 
right the first time.

I think it's more valuable to users to get a basic network driver that 
pings or a basic ATA driver that reads/writes, than peripheral issues 
like suspend/resume.

Certainly we should ask for it, but it shouldn't be a merge-stopper.

	Jeff

Re: NAK new drivers without proper power management?

[Willy Tarreau]

On Fri, Feb 09, 2007 at 07:25:34PM -0500, Jeff Garzik wrote:
> Nigel Cunningham wrote:
> >Hi.
> >
> >On Fri, 2007-02-09 at 23:17 +0100, Arjan van de Ven wrote:
> >>On Sat, 2007-02-10 at 08:57 +1100, Nigel Cunningham wrote:
> >>>Hi.
> >>>
> >>>I don't think this is already done (feel free to correct me if I'm
> >>>wrong)..
> >>>
> >>>Can we start to NAK new drivers that don't have proper power management
> >>>implemented? There really is no excuse for writing a new driver and not
> >>>putting .suspend and .resume methods in anymore, is there?
> >>
> >>to a large degree, a device driver that doesn't suspend is better than
> >>no device driver at all, right?
> >
> >I'm not sure it is. It only makes more work for everyone else: We have
> >to help people figure out what causes their computer to fail to resume
> >(which can take quite a while), then get them them complain to driver
> >author, and the driver author has to submit patches to fix it.
> >
> >All of this is avoided if they'll just do it right in the first place.
> 
> A lot of a lot of things could have been avoided, if they just did it 
> right the first time.
> 
> I think it's more valuable to users to get a basic network driver that 
> pings or a basic ATA driver that reads/writes, than peripheral issues 
> like suspend/resume.

100% agreed.

I've been used to a notebook (VAIO) which did not correctly shut down, and
did not support reboot. Now the one I have behaves normally on both features.
I've never ever felt the need for suspend/resume, that I've always attributed
to "geeks" requirements. I had to debug the shutdown code myself for the
previous notebook, and discovered that it was caused by bugs in the ACPI
state transitions for suspend and such fancy features. I would really have
prefered that the people writing the ACPI code had focused first on power-on/
power-off before the rest.

> Certainly we should ask for it, but it shouldn't be a merge-stopper.

I think we should even proceed in the opposite direction : refuse to suspend
if at least one driver does not support the feature, and enumerate the
faulty drivers on the console. While I agree that a machine which resumes
in a bad state is not funny at all to debug, at least when the user expects
his notebook to suspend and sees that it refuses, he can complain about the
drivers which do not support it, and can even unload them first if unneeded.

Regards,
Willy

Re: NAK new drivers without proper power management?

[Tilman Schmidt]

[-- Attachment #1: Type: text/plain, Size: 1073 bytes --]

Am 10.02.2007 07:43 schrieb Willy Tarreau:
> On Fri, Feb 09, 2007 at 07:25:34PM -0500, Jeff Garzik wrote:

>>>> On Sat, 2007-02-10 at 08:57 +1100, Nigel Cunningham wrote:
>>>>> Can we start to NAK new drivers that don't have proper power management
>>>>> implemented?
[...]
>> Certainly we should ask for it, but it shouldn't be a merge-stopper.
> 
> I think we should even proceed in the opposite direction : refuse to suspend
> if at least one driver does not support the feature, and enumerate the
> faulty drivers on the console. While I agree that a machine which resumes
> in a bad state is not funny at all to debug, at least when the user expects
> his notebook to suspend and sees that it refuses, he can complain about the
> drivers which do not support it, and can even unload them first if unneeded.

I agree wholeheartedly. That's the correct way to handle this.

-- 
Tilman Schmidt                          E-Mail: tilman@imap.cc
Bonn, Germany
- In theory, there is no difference between theory and practice.
  In practice, there is.


[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 253 bytes --]

Re: NAK new drivers without proper power management?

[Arjan van de Ven]

> > 
> > to a large degree, a device driver that doesn't suspend is better than
> > no device driver at all, right?
> 
> I'm not sure it is. It only makes more work for everyone else: We have
> to help people figure out what causes their computer to fail to resume
> (which can take quite a while), 

so we make the kernel printk on suspend if there are devices without
suspend/resume. Heck, make a config option that prints that at modprobe
time.


-- 
if you want to mail me at work (you don't), use arjan (at) linux.intel.com
Test the interaction between Linux and your BIOS via http://www.linuxfirmwarekit.org

Re: NAK new drivers without proper power management?

[Pavel Machek]

Hi!

> > I don't think this is already done (feel free to correct me if I'm
> > wrong)..
> > 
> > Can we start to NAK new drivers that don't have proper power management
> > implemented? There really is no excuse for writing a new driver and not
> > putting .suspend and .resume methods in anymore, is there?
> 
> to a large degree, a device driver that doesn't suspend is better than
> no device driver at all, right?
> now.. if you want to make the core warn about it, that's very fair

Well, driver that is broken on SMP is arguably better than no driver
at all, yet we'd probably avoid merging that. It would be nice to
start including suspend in 'must work' list...
							Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

Re: NAK new drivers without proper power management?

[Rafael J. Wysocki]

Hi,

On Saturday, 10 February 2007 20:38, Pavel Machek wrote:
> Hi!
> 
> > > I don't think this is already done (feel free to correct me if I'm
> > > wrong)..
> > > 
> > > Can we start to NAK new drivers that don't have proper power management
> > > implemented? There really is no excuse for writing a new driver and not
> > > putting .suspend and .resume methods in anymore, is there?
> > 
> > to a large degree, a device driver that doesn't suspend is better than
> > no device driver at all, right?
> > now.. if you want to make the core warn about it, that's very fair
> 
> Well, driver that is broken on SMP is arguably better than no driver
> at all, yet we'd probably avoid merging that. It would be nice to
> start including suspend in 'must work' list...

What about this:

"If the device requires that, implement .suspend and .resume or at least
define .suspend that will always return -ENOSYS (then people will know they
have to unload the driver before the suspend).  Similarly, if you aren't sure
whether or not the device requires .suspend and .resume, define .suspend that
will always return -ENOSYS."

Greetings,
Rafael


-- 
If you don't have the time to read,
you don't have the time or the tools to write.
		- Stephen King

Re: NAK new drivers without proper power management?

[Nigel Cunningham]

Hi.

On Sat, 2007-02-10 at 23:20 +0100, Rafael J. Wysocki wrote:
> Hi,
> 
> On Saturday, 10 February 2007 20:38, Pavel Machek wrote:
> > Hi!
> > 
> > > > I don't think this is already done (feel free to correct me if I'm
> > > > wrong)..
> > > > 
> > > > Can we start to NAK new drivers that don't have proper power management
> > > > implemented? There really is no excuse for writing a new driver and not
> > > > putting .suspend and .resume methods in anymore, is there?
> > > 
> > > to a large degree, a device driver that doesn't suspend is better than
> > > no device driver at all, right?
> > > now.. if you want to make the core warn about it, that's very fair
> > 
> > Well, driver that is broken on SMP is arguably better than no driver
> > at all, yet we'd probably avoid merging that. It would be nice to
> > start including suspend in 'must work' list...
> 
> What about this:
> 
> "If the device requires that, implement .suspend and .resume or at least
> define .suspend that will always return -ENOSYS (then people will know they
> have to unload the driver before the suspend).  Similarly, if you aren't sure
> whether or not the device requires .suspend and .resume, define .suspend that
> will always return -ENOSYS."

If your device requires power management, and you know it requires power
management, why not just implement power management? Doing -ENOSYS
instead is like saying -ESPAMMEBECAUSEIMLAZY.

Let me put it another way: People keep talking about Linux being ready
for the desktop. To me at least (but I dare say for lots of other people
too), being ready for the desktop means that things just work, without
having to recompile kernels or bug driver authors or wait twelve
months. 

And it means that doing a bare minimum isn't enough. We keep claiming
that Open Source is better than Proprietary software. If we accept
half-pie jobs of implementing support for anything - driver power
management support or hibernation support or whatever - as 'good
enough', we're undercutting that argument. Linux's power management
support should - as far as we're able - be at least as good as that
other operating system's and preferably way, way better.

-ENOSYS is just not acceptable.

Regards,

Nigel

Re: NAK new drivers without proper power management?

[Tilman Schmidt]

[-- Attachment #1: Type: text/plain, Size: 2364 bytes --]

Am 10.02.2007 23:37 schrieb Nigel Cunningham:
> If your device requires power management, and you know it requires power
> management, why not just implement power management? Doing -ENOSYS
> instead is like saying -ESPAMMEBECAUSEIMLAZY.

Like it or not, power management is far from trivial, and people
writing device drivers have limited resources. Calling them lazy
does not help that in the least. If you try to put pressure on them
by refusing to merge their work as long as it doesn't provide this
or that functionality, you *may* end up with a few drivers having
that functionality which otherwise wouldn't, but you *will* also
end up with a number of drivers never making it into the kernel
because their authors just have to give up.

Also, in your argument you neglected a few cases:
- What if my device does not require power management?
- What if I don't know whether my device requires power management?
- What if I know my device would require power management, but don't
  know how to implement it?

> Let me put it another way: People keep talking about Linux being ready
> for the desktop. To me at least (but I dare say for lots of other people
> too), being ready for the desktop means that things just work, without
> having to recompile kernels or bug driver authors or wait twelve
> months. 

Exactly.

> And it means that doing a bare minimum isn't enough. We keep claiming
> that Open Source is better than Proprietary software. If we accept
> half-pie jobs of implementing support for anything - driver power
> management support or hibernation support or whatever - as 'good
> enough', we're undercutting that argument. Linux's power management
> support should - as far as we're able - be at least as good as that
> other operating system's and preferably way, way better.
> 
> -ENOSYS is just not acceptable.

Your argument falls down the moment you consider the alternative:
not merging the driver means that the device won't work at all.
(Given that out-of-tree drivers are actively discouraged, to put
it mildly.) That's arguably farther from "desktop readiness" than
a device not supporting power management.

-- 
Tilman Schmidt                          E-Mail: tilman@imap.cc
Bonn, Germany
- In theory, there is no difference between theory and practice.
  In practice, there is.


[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 253 bytes --]

Re: NAK new drivers without proper power management?

[Rafael J. Wysocki]

On Sunday, 11 February 2007 00:45, Tilman Schmidt wrote:
> Am 10.02.2007 23:37 schrieb Nigel Cunningham:
> > If your device requires power management, and you know it requires power
> > management, why not just implement power management? Doing -ENOSYS
> > instead is like saying -ESPAMMEBECAUSEIMLAZY.
> 
> Like it or not, power management is far from trivial, and people
> writing device drivers have limited resources. Calling them lazy
> does not help that in the least. If you try to put pressure on them
> by refusing to merge their work as long as it doesn't provide this
> or that functionality, you *may* end up with a few drivers having
> that functionality which otherwise wouldn't, but you *will* also
> end up with a number of drivers never making it into the kernel
> because their authors just have to give up.
> 
> Also, in your argument you neglected a few cases:
> - What if my device does not require power management?
> - What if I don't know whether my device requires power management?
> - What if I know my device would require power management, but don't
>   know how to implement it?

Plus:
- What if I'm planning to implement the power managemet, but not just right
now?
 
> > Let me put it another way: People keep talking about Linux being ready
> > for the desktop. To me at least (but I dare say for lots of other people
> > too), being ready for the desktop means that things just work, without
> > having to recompile kernels or bug driver authors or wait twelve
> > months. 
> 
> Exactly.
> 
> > And it means that doing a bare minimum isn't enough. We keep claiming
> > that Open Source is better than Proprietary software. If we accept
> > half-pie jobs of implementing support for anything - driver power
> > management support or hibernation support or whatever - as 'good
> > enough', we're undercutting that argument. Linux's power management
> > support should - as far as we're able - be at least as good as that
> > other operating system's and preferably way, way better.
> > 
> > -ENOSYS is just not acceptable.
> 
> Your argument falls down the moment you consider the alternative:
> not merging the driver means that the device won't work at all.
> (Given that out-of-tree drivers are actively discouraged, to put
> it mildly.) That's arguably farther from "desktop readiness" than
> a device not supporting power management.

Agreed.

Greetings,
Rafael

Re: NAK new drivers without proper power management?

[Nigel Cunningham]

On Sun, 2007-02-11 at 01:27 +0100, Rafael J. Wysocki wrote:
> On Sunday, 11 February 2007 00:45, Tilman Schmidt wrote:
> > Am 10.02.2007 23:37 schrieb Nigel Cunningham:
> > > If your device requires power management, and you know it requires power
> > > management, why not just implement power management? Doing -ENOSYS
> > > instead is like saying -ESPAMMEBECAUSEIMLAZY.
> > 
> > Like it or not, power management is far from trivial, and people
> > writing device drivers have limited resources. Calling them lazy
> > does not help that in the least. If you try to put pressure on them
> > by refusing to merge their work as long as it doesn't provide this
> > or that functionality, you *may* end up with a few drivers having
> > that functionality which otherwise wouldn't, but you *will* also
> > end up with a number of drivers never making it into the kernel
> > because their authors just have to give up.
> > 
> > Also, in your argument you neglected a few cases:
> > - What if my device does not require power management?
> > - What if I don't know whether my device requires power management?
> > - What if I know my device would require power management, but don't
> >   know how to implement it?
> 
> Plus:
> - What if I'm planning to implement the power managemet, but not just right
> now?

Why not right now?
 
Regards,

Nigel

Re: NAK new drivers without proper power management?

[Mark Lord]

Nigel Cunningham wrote:
> On Sun, 2007-02-11 at 01:27 +0100, Rafael J. Wysocki wrote:
>> Plus:
>> - What if I'm planning to implement the power managemet, but not just right
>> now?
> 
> Why not right now?

LKML is much more receptive to drivers that follow
the "release early, release often" mantra.

Which means we really have to be more accomodating of
drivers that start out simple, and then gain all of the
non-essential capabilities gradually over time.

Simple observation here shows much more hostility :)
to drivers that are simply "presented" as a complete whole.
Often for good reason -- starting out with a framework
and then adding the rest bit by bit allows for much better
peer review and feedback.

And not all devices / situations need power management,
and lack of documentation on the hardware often prevents
us from implementing it at the outset.

Cheers

Re: NAK new drivers without proper power management?

[Christoph Hellwig]

On Tue, Feb 13, 2007 at 10:55:18AM -0500, Mark Lord wrote:
> LKML is much more receptive to drivers that follow
> the "release early, release often" mantra.

Exactly.

> Which means we really have to be more accomodating of
> drivers that start out simple, and then gain all of the
> non-essential capabilities gradually over time.

We usually are, the endless flamewar lurkers might not :)
> 
> Simple observation here shows much more hostility :)
> to drivers that are simply "presented" as a complete whole.
> Often for good reason -- starting out with a framework
> and then adding the rest bit by bit allows for much better
> peer review and feedback.

*nod*

> And not all devices / situations need power management,
> and lack of documentation on the hardware often prevents
> us from implementing it at the outset.

*nod*

So can be use Mark's excellent post as closing of this
utterly useless thread and go on to real work now?

Re: NAK new drivers without proper power management?

[Nigel Cunningham]

Hi.

On Sun, 2007-02-11 at 00:45 +0100, Tilman Schmidt wrote:
> Am 10.02.2007 23:37 schrieb Nigel Cunningham:
> > If your device requires power management, and you know it requires power
> > management, why not just implement power management? Doing -ENOSYS
> > instead is like saying -ESPAMMEBECAUSEIMLAZY.
> 
> Like it or not, power management is far from trivial, and people
> writing device drivers have limited resources. Calling them lazy
> does not help that in the least. If you try to put pressure on them
> by refusing to merge their work as long as it doesn't provide this
> or that functionality, you *may* end up with a few drivers having
> that functionality which otherwise wouldn't, but you *will* also
> end up with a number of drivers never making it into the kernel
> because their authors just have to give up.

It's not that complex. All we're really talking about is a bit of extra
code to cleanup and configure hardware state; things that the driver
author already knows how to do. S3 might require a bit more
initialisation if firmware needs to be reloaded or more extensive
configuration needs to be done, but if there's firmware to be loaded,
there is a reasonably good probability that we loaded it from Linux to
start with anyway.

> Also, in your argument you neglected a few cases:
> - What if my device does not require power management?

Then you as a generic routine that does nothing but return success
(potentially shared with other drivers that are in the same situation).

> - What if I don't know whether my device requires power management?

The questions are straight forward: Is there hardware state that needs
to be configured if you've just booted the computer and nothing else has
touched it? If so, that needs to be done in a resume method. Do you need
to clean up state prior to doing the things in the resume method, or
otherwise do things to quiesce the driver? If so, they will need to be
done in the suspend method. The result will be roughly similar to what
you do for module load/unload, except maybe less complete in some cases.

> - What if I know my device would require power management, but don't
>   know how to implement it?

I've just told you above :) Now you know!

> > Let me put it another way: People keep talking about Linux being ready
> > for the desktop. To me at least (but I dare say for lots of other people
> > too), being ready for the desktop means that things just work, without
> > having to recompile kernels or bug driver authors or wait twelve
> > months. 
> 
> Exactly.
> 
> > And it means that doing a bare minimum isn't enough. We keep claiming
> > that Open Source is better than Proprietary software. If we accept
> > half-pie jobs of implementing support for anything - driver power
> > management support or hibernation support or whatever - as 'good
> > enough', we're undercutting that argument. Linux's power management
> > support should - as far as we're able - be at least as good as that
> > other operating system's and preferably way, way better.
> > 
> > -ENOSYS is just not acceptable.
> 
> Your argument falls down the moment you consider the alternative:
> not merging the driver means that the device won't work at all.
> (Given that out-of-tree drivers are actively discouraged, to put
> it mildly.) That's arguably farther from "desktop readiness" than
> a device not supporting power management.

I disagree (but I would, of course!). If we apply your logic
consistently, we should merge the driver as soon as any code is written
for it (anything is better than nothing). I'm simply arguing that a
driver that handling suspend and resume should be as much of a
requirement as not causing memory corruption or such like are.

Regards,

Nigel

Re: NAK new drivers without proper power management?

[Tilman Schmidt]

[-- Attachment #1: Type: text/plain, Size: 4387 bytes --]

Hi,

Am 11.02.2007 23:37 schrieb Nigel Cunningham:
> On Sun, 2007-02-11 at 00:45 +0100, Tilman Schmidt wrote:
>> Am 10.02.2007 23:37 schrieb Nigel Cunningham:
>>> If your device requires power management, and you know it requires power
>>> management, why not just implement power management? [...]
>> Like it or not, power management is far from trivial, and people
>> writing device drivers have limited resources. [...]
> It's not that complex. All we're really talking about is a bit of extra
> code to cleanup and configure hardware state; things that the driver
> author already knows how to do. S3 might require a bit more
> initialisation if firmware needs to be reloaded or more extensive
> configuration needs to be done, but if there's firmware to be loaded,
> there is a reasonably good probability that we loaded it from Linux to
> start with anyway.

You are assuming a perfect world where driver authors have complete
knowledge of their devices. In reality, many drivers (including
those I have the mixed pleasure of maintaining) are based at least
in part on reverse engineering, and managing power states may well
fall into the domain of things not yet sufficiently reverse
engineered.

>> Also, in your argument you neglected a few cases:
>> - What if my device does not require power management?
> 
> Then you as a generic routine that does nothing but return success
> (potentially shared with other drivers that are in the same situation).

But if I just write an empty routine like that I open myself up to
criticism along the lines of "writing dummy routines just in order
to shut up kernel warnings". BTDT.

>> - What if I don't know whether my device requires power management?
> 
> The questions are straight forward: Is there hardware state that needs
> to be configured if you've just booted the computer and nothing else has
> touched it? If so, that needs to be done in a resume method. Do you need
> to clean up state prior to doing the things in the resume method, or
> otherwise do things to quiesce the driver? If so, they will need to be
> done in the suspend method. The result will be roughly similar to what
> you do for module load/unload, except maybe less complete in some cases.

I don't doubt your basic assessment. However it doesn't translate that
easily into a real implementation. In my case, I maintain a USB driver,
so I have to deal with USB specifics of suspend/resume which happen not
to be that well documented. My driver provides an isdn4linux device but
isdn4linux knows nothing about suspend/resume so I am on my own on how
to reconcile the two. The device itself, though in turn far from trivial,
is actually the least of my worries.

>> - What if I know my device would require power management, but don't
>>   know how to implement it?
> 
> I've just told you above :) Now you know!

No I don't. See above.

>>> -ENOSYS is just not acceptable.
>> Your argument falls down the moment you consider the alternative:
>> not merging the driver means that the device won't work at all.
>> (Given that out-of-tree drivers are actively discouraged, to put
>> it mildly.) That's arguably farther from "desktop readiness" than
>> a device not supporting power management.
> 
> I disagree (but I would, of course!). If we apply your logic
> consistently, we should merge the driver as soon as any code is written
> for it (anything is better than nothing). I'm simply arguing that a
> driver that handling suspend and resume should be as much of a
> requirement as not causing memory corruption or such like are.

Well, that's a common fallacy about applying any logic consistently.
There's a continuum of usefulness from "hardly works at all" through
"causes random memory corruption", "doesn't support power management",
and "does not support some esoteric protocol variety no one ever heard
of anyways" up to "supports any and all uses to which anyone could
possibly want to put the device". I would argue that "doesn't support
power management" is *much* farther up that ladder than, for example,
"causes random memory corruption".

Regards,
Tilman

-- 
Tilman Schmidt                          E-Mail: tilman@imap.cc
Bonn, Germany
Diese Nachricht besteht zu 100% aus wiederverwerteten Bits.
Ungeöffnet mindestens haltbar bis: (siehe Rückseite)


[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 253 bytes --]

Re: NAK new drivers without proper power management?

[Rafael J. Wysocki]

Hi,

On Monday, 12 February 2007 01:10, Tilman Schmidt wrote:
> Hi,
> 
> Am 11.02.2007 23:37 schrieb Nigel Cunningham:
> > On Sun, 2007-02-11 at 00:45 +0100, Tilman Schmidt wrote:
> >> Am 10.02.2007 23:37 schrieb Nigel Cunningham:
> >>> If your device requires power management, and you know it requires power
> >>> management, why not just implement power management? [...]
> >> Like it or not, power management is far from trivial, and people
> >> writing device drivers have limited resources. [...]
> > It's not that complex. All we're really talking about is a bit of extra
> > code to cleanup and configure hardware state; things that the driver
> > author already knows how to do. S3 might require a bit more
> > initialisation if firmware needs to be reloaded or more extensive
> > configuration needs to be done, but if there's firmware to be loaded,
> > there is a reasonably good probability that we loaded it from Linux to
> > start with anyway.
> 
> You are assuming a perfect world where driver authors have complete
> knowledge of their devices. In reality, many drivers (including
> those I have the mixed pleasure of maintaining) are based at least
> in part on reverse engineering, and managing power states may well
> fall into the domain of things not yet sufficiently reverse
> engineered.

Exactly.

> >> Also, in your argument you neglected a few cases:
> >> - What if my device does not require power management?
> > 
> > Then you as a generic routine that does nothing but return success
> > (potentially shared with other drivers that are in the same situation).
> 
> But if I just write an empty routine like that I open myself up to
> criticism along the lines of "writing dummy routines just in order
> to shut up kernel warnings". BTDT.

Well, for me the design that required driver authors to write empty routines
returning success, would be bad.

> >> - What if I don't know whether my device requires power management?
> > 
> > The questions are straight forward: Is there hardware state that needs
> > to be configured if you've just booted the computer and nothing else has
> > touched it? If so, that needs to be done in a resume method. Do you need
> > to clean up state prior to doing the things in the resume method, or
> > otherwise do things to quiesce the driver? If so, they will need to be
> > done in the suspend method. The result will be roughly similar to what
> > you do for module load/unload, except maybe less complete in some cases.
> 
> I don't doubt your basic assessment. However it doesn't translate that
> easily into a real implementation. In my case, I maintain a USB driver,
> so I have to deal with USB specifics of suspend/resume which happen not
> to be that well documented. My driver provides an isdn4linux device but
> isdn4linux knows nothing about suspend/resume so I am on my own on how
> to reconcile the two. The device itself, though in turn far from trivial,
> is actually the least of my worries.
> 
> >> - What if I know my device would require power management, but don't
> >>   know how to implement it?
> > 
> > I've just told you above :) Now you know!
> 
> No I don't. See above.
> 
> >>> -ENOSYS is just not acceptable.
> >> Your argument falls down the moment you consider the alternative:
> >> not merging the driver means that the device won't work at all.
> >> (Given that out-of-tree drivers are actively discouraged, to put
> >> it mildly.) That's arguably farther from "desktop readiness" than
> >> a device not supporting power management.
> > 
> > I disagree (but I would, of course!). If we apply your logic
> > consistently, we should merge the driver as soon as any code is written
> > for it (anything is better than nothing). I'm simply arguing that a
> > driver that handling suspend and resume should be as much of a
> > requirement as not causing memory corruption or such like are.
> 
> Well, that's a common fallacy about applying any logic consistently.
> There's a continuum of usefulness from "hardly works at all" through
> "causes random memory corruption", "doesn't support power management",
> and "does not support some esoteric protocol variety no one ever heard
> of anyways" up to "supports any and all uses to which anyone could
> possibly want to put the device". I would argue that "doesn't support
> power management" is *much* farther up that ladder than, for example,
> "causes random memory corruption".

 I agree with that.  Moreover, I think that the suspend/resume support is
something you _can_ _live_ without while living, for instance, without
networking at all would be difficult these days. Therefore I would certainly
accept the driver that didn't support suspend/resume for my network adapter
and I'd be happy to use it anyway.

On the other hand, it would be nice if that driver did something that would
prevent the system from suspending when it's loaded, just in case.

Greetings,
Rafael

Re: NAK new drivers without proper power management?

[Nigel Cunningham]

Howdy!

On Mon, 2007-02-12 at 01:10 +0100, Tilman Schmidt wrote:
> Hi,
> 
> Am 11.02.2007 23:37 schrieb Nigel Cunningham:
> > On Sun, 2007-02-11 at 00:45 +0100, Tilman Schmidt wrote:
> >> Am 10.02.2007 23:37 schrieb Nigel Cunningham:
> >>> If your device requires power management, and you know it requires power
> >>> management, why not just implement power management? [...]
> >> Like it or not, power management is far from trivial, and people
> >> writing device drivers have limited resources. [...]
> > It's not that complex. All we're really talking about is a bit of extra
> > code to cleanup and configure hardware state; things that the driver
> > author already knows how to do. S3 might require a bit more
> > initialisation if firmware needs to be reloaded or more extensive
> > configuration needs to be done, but if there's firmware to be loaded,
> > there is a reasonably good probability that we loaded it from Linux to
> > start with anyway.
> 
> You are assuming a perfect world where driver authors have complete
> knowledge of their devices. In reality, many drivers (including
> those I have the mixed pleasure of maintaining) are based at least
> in part on reverse engineering, and managing power states may well
> fall into the domain of things not yet sufficiently reverse
> engineered.

Nope. I'm assuming that the driver author knows what needs to be done to
get the driver out of whatever state the BIOS puts it in to start with,
and into an operational state, and that they therefore also know what
needs to be done to take it out of the operational state again. I'm
admitting that there's also another state - the post suspend-to-ram
driver state - that they may not know how to deal with. But for
suspend-to-disk, if you know how to get the driver to work in the first
place, you know enough to stop it working (.suspend) and start it up
again (.resume) for the hibernate case at least.

I'm not assuming that you know enough to be able to put the driver into
a low state and get it out again. This is definitely preferable, and at
least possibly essential for suspend to ram, but for some unknown reason
I'm quite hibernation focused, and for that, just the above is
sufficient.

> >> Also, in your argument you neglected a few cases:
> >> - What if my device does not require power management?
> > 
> > Then you as a generic routine that does nothing but return success
> > (potentially shared with other drivers that are in the same situation).
> 
> But if I just write an empty routine like that I open myself up to
> criticism along the lines of "writing dummy routines just in order
> to shut up kernel warnings". BTDT.

Well, it might not be completely empty. I think someone already pointed
out that there's a minimal workset for the pci bus that pci drivers
would want to invoke. But we wouldn't (rightly) accuse you of such
things if we decided that the policy was "Every driver ought to have a
resume routine, even if it's just a minimal I-just-work route".

> >> - What if I don't know whether my device requires power management?
> > 
> > The questions are straight forward: Is there hardware state that needs
> > to be configured if you've just booted the computer and nothing else has
> > touched it? If so, that needs to be done in a resume method. Do you need
> > to clean up state prior to doing the things in the resume method, or
> > otherwise do things to quiesce the driver? If so, they will need to be
> > done in the suspend method. The result will be roughly similar to what
> > you do for module load/unload, except maybe less complete in some cases.
> 
> I don't doubt your basic assessment. However it doesn't translate that
> easily into a real implementation. In my case, I maintain a USB driver,
> so I have to deal with USB specifics of suspend/resume which happen not
> to be that well documented. My driver provides an isdn4linux device but
> isdn4linux knows nothing about suspend/resume so I am on my own on how
> to reconcile the two. The device itself, though in turn far from trivial,
> is actually the least of my worries.

Mmm, so that's a case where we need to prod those who write
documentation and bus support first. You're probably closer! :)

Regards,

Nigel

Re: NAK new drivers without proper power management?

[Rafael J. Wysocki]

On Monday, 12 February 2007 05:08, Nigel Cunningham wrote:
> Howdy!
> 
> On Mon, 2007-02-12 at 01:10 +0100, Tilman Schmidt wrote:
> > Hi,
> > 
> > Am 11.02.2007 23:37 schrieb Nigel Cunningham:
> > > On Sun, 2007-02-11 at 00:45 +0100, Tilman Schmidt wrote:
> > >> Am 10.02.2007 23:37 schrieb Nigel Cunningham:
> > >>> If your device requires power management, and you know it requires power
> > >>> management, why not just implement power management? [...]
> > >> Like it or not, power management is far from trivial, and people
> > >> writing device drivers have limited resources. [...]
> > > It's not that complex. All we're really talking about is a bit of extra
> > > code to cleanup and configure hardware state; things that the driver
> > > author already knows how to do. S3 might require a bit more
> > > initialisation if firmware needs to be reloaded or more extensive
> > > configuration needs to be done, but if there's firmware to be loaded,
> > > there is a reasonably good probability that we loaded it from Linux to
> > > start with anyway.
> > 
> > You are assuming a perfect world where driver authors have complete
> > knowledge of their devices. In reality, many drivers (including
> > those I have the mixed pleasure of maintaining) are based at least
> > in part on reverse engineering, and managing power states may well
> > fall into the domain of things not yet sufficiently reverse
> > engineered.
> 
> Nope. I'm assuming that the driver author knows what needs to be done to
> get the driver out of whatever state the BIOS puts it in to start with,
> and into an operational state, and that they therefore also know what
> needs to be done to take it out of the operational state again. I'm
> admitting that there's also another state - the post suspend-to-ram
> driver state - that they may not know how to deal with. But for
> suspend-to-disk, if you know how to get the driver to work in the first
> place, you know enough to stop it working (.suspend) and start it up
> again (.resume) for the hibernate case at least.

We're talking about _both_ the STR and STD.  The drivers that have problems
with the STR cannot be regarded as suspend/resume-safe IMO.

> I'm not assuming that you know enough to be able to put the driver into
> a low state and get it out again. This is definitely preferable, and at
> least possibly essential for suspend to ram, but for some unknown reason
> I'm quite hibernation focused, and for that, just the above is
> sufficient.

Please take the STR into consideration too.  After all we use the same
suspend/resume code for both STD and STR so it should work with both.  If it
doesn't work with one of them, we have a problem.

> > >> Also, in your argument you neglected a few cases:
> > >> - What if my device does not require power management?
> > > 
> > > Then you as a generic routine that does nothing but return success
> > > (potentially shared with other drivers that are in the same situation).
> > 
> > But if I just write an empty routine like that I open myself up to
> > criticism along the lines of "writing dummy routines just in order
> > to shut up kernel warnings". BTDT.
> 
> Well, it might not be completely empty. I think someone already pointed
> out that there's a minimal workset for the pci bus that pci drivers
> would want to invoke. But we wouldn't (rightly) accuse you of such
> things if we decided that the policy was "Every driver ought to have a
> resume routine, even if it's just a minimal I-just-work route".

I'm still thinking that would be wasteful.  I think there are more drivers that
work than there are drivers that don't work.

> > >> - What if I don't know whether my device requires power management?
> > > 
> > > The questions are straight forward: Is there hardware state that needs
> > > to be configured if you've just booted the computer and nothing else has
> > > touched it? If so, that needs to be done in a resume method. Do you need
> > > to clean up state prior to doing the things in the resume method, or
> > > otherwise do things to quiesce the driver? If so, they will need to be
> > > done in the suspend method. The result will be roughly similar to what
> > > you do for module load/unload, except maybe less complete in some cases.
> > 
> > I don't doubt your basic assessment. However it doesn't translate that
> > easily into a real implementation. In my case, I maintain a USB driver,
> > so I have to deal with USB specifics of suspend/resume which happen not
> > to be that well documented. My driver provides an isdn4linux device but
> > isdn4linux knows nothing about suspend/resume so I am on my own on how
> > to reconcile the two. The device itself, though in turn far from trivial,
> > is actually the least of my worries.
> 
> Mmm, so that's a case where we need to prod those who write
> documentation and bus support first. You're probably closer! :)

Actually, the lack of documentation is a major problem that we all should
try to fix in the first place.  Unfortunately the code has been recently
changing quite often, so that's difficult.

Greetings,
Rafael

Re: NAK new drivers without proper power management?

[Nigel Cunningham]

Hi.

On Mon, 2007-02-12 at 21:06 +0100, Rafael J. Wysocki wrote:
> On Monday, 12 February 2007 05:08, Nigel Cunningham wrote:
> > Nope. I'm assuming that the driver author knows what needs to be done to
> > get the driver out of whatever state the BIOS puts it in to start with,
> > and into an operational state, and that they therefore also know what
> > needs to be done to take it out of the operational state again. I'm
> > admitting that there's also another state - the post suspend-to-ram
> > driver state - that they may not know how to deal with. But for
> > suspend-to-disk, if you know how to get the driver to work in the first
> > place, you know enough to stop it working (.suspend) and start it up
> > again (.resume) for the hibernate case at least.
> 
> We're talking about _both_ the STR and STD.  The drivers that have problems
> with the STR cannot be regarded as suspend/resume-safe IMO.

Yeah, I'm not disagreeing at all. I'm just admitting my bias toward the
bit I concentrate on more.

[...]

> > Mmm, so that's a case where we need to prod those who write
> > documentation and bus support first. You're probably closer! :)
> 
> Actually, the lack of documentation is a major problem that we all should
> try to fix in the first place.  Unfortunately the code has been recently
> changing quite often, so that's difficult.

Yeah.

Nigel

Suspend/resume semantics for ISDN drivers (was: NAK new drivers without proper power management?)

[Tilman Schmidt]

[-- Attachment #1: Type: text/plain, Size: 1207 bytes --]

Ok, I've thought some more but I still don't know ...

On 12.02.2007 01:10 I wrote:
> I don't doubt your basic assessment. However it doesn't translate that
> easily into a real implementation. In my case, I maintain a USB driver,
> so I have to deal with USB specifics of suspend/resume which happen not
> to be that well documented. My driver provides an isdn4linux device but
> isdn4linux knows nothing about suspend/resume so I am on my own on how
> to reconcile the two. The device itself, though in turn far from trivial,
> is actually the least of my worries.

So, how *should* an isdn4linux driver handle a request to suspend?
Specifically, if there are active connections, should it try to
shut them down in an orderly fashion (which might imply some delays
waiting for the remote station to acknowledge, etc.)? Should it kill
them abruptly (as for a USB unplug event)? Or should it just refuse
to suspend while a connection is still active?

Thanks for any insights,
Tilman

-- 
Tilman Schmidt                          E-Mail: tilman@imap.cc
Bonn, Germany
Diese Nachricht besteht zu 100% aus wiederverwerteten Bits.
Ungeöffnet mindestens haltbar bis: (siehe Rückseite)


[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 253 bytes --]

Re: Suspend/resume semantics for ISDN drivers (was: NAK new drivers without proper power management?)

[Rafael J. Wysocki]

On Saturday, 3 March 2007 23:48, Tilman Schmidt wrote:
> Ok, I've thought some more but I still don't know ...
> 
> On 12.02.2007 01:10 I wrote:
> > I don't doubt your basic assessment. However it doesn't translate that
> > easily into a real implementation. In my case, I maintain a USB driver,
> > so I have to deal with USB specifics of suspend/resume which happen not
> > to be that well documented. My driver provides an isdn4linux device but
> > isdn4linux knows nothing about suspend/resume so I am on my own on how
> > to reconcile the two. The device itself, though in turn far from trivial,
> > is actually the least of my worries.
> 
> So, how *should* an isdn4linux driver handle a request to suspend?
> Specifically, if there are active connections, should it try to
> shut them down in an orderly fashion (which might imply some delays
> waiting for the remote station to acknowledge, etc.)? Should it kill
> them abruptly (as for a USB unplug event)? Or should it just refuse
> to suspend while a connection is still active?

I think that refusing to suspend wouldn't be a good approach (think of an
emergency suspend when the battery is running low).

Probably the closing of connections would be the nicest thing from the
user's point of view.

Greetings,
Rafael

Re: Suspend/resume semantics for ISDN drivers (was: NAK new drivers without proper power management?)

[Pavel Machek]

Hi!

> > On 12.02.2007 01:10 I wrote:
> > > I don't doubt your basic assessment. However it doesn't translate that
> > > easily into a real implementation. In my case, I maintain a USB driver,
> > > so I have to deal with USB specifics of suspend/resume which happen not
> > > to be that well documented. My driver provides an isdn4linux device but
> > > isdn4linux knows nothing about suspend/resume so I am on my own on how
> > > to reconcile the two. The device itself, though in turn far from trivial,
> > > is actually the least of my worries.
> > 
> > So, how *should* an isdn4linux driver handle a request to suspend?
> > Specifically, if there are active connections, should it try to
> > shut them down in an orderly fashion (which might imply some delays
> > waiting for the remote station to acknowledge, etc.)? Should it kill
> > them abruptly (as for a USB unplug event)? Or should it just refuse
> > to suspend while a connection is still active?
> 
> I think that refusing to suspend wouldn't be a good approach (think of an
> emergency suspend when the battery is running low).
> 
> Probably the closing of connections would be the nicest thing from the
> user's point of view.

It depends on "how long does connection close take". If it is more
than few seconds, kill them abruptly.
								Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

Re: NAK new drivers without proper power management?

[Willy Tarreau]

Hi Nigel,

On Sun, Feb 11, 2007 at 09:37:06AM +1100, Nigel Cunningham wrote:
> On Sat, 2007-02-10 at 23:20 +0100, Rafael J. Wysocki wrote:
(...)
> > What about this:
> > 
> > "If the device requires that, implement .suspend and .resume or at least
> > define .suspend that will always return -ENOSYS (then people will know they
> > have to unload the driver before the suspend).  Similarly, if you aren't sure
> > whether or not the device requires .suspend and .resume, define .suspend that
> > will always return -ENOSYS."
> 
> If your device requires power management, and you know it requires power
> management, why not just implement power management? Doing -ENOSYS
> instead is like saying -ESPAMMEBECAUSEIMLAZY.

No, it means "Not implemented because I don't want to screw that driver with
something I'm not expert in". And it also means "Other people will quickly
notice it and will know how to fix this if they really need it".

> Let me put it another way: People keep talking about Linux being ready
> for the desktop. To me at least (but I dare say for lots of other people
> too), being ready for the desktop means that things just work, without
> having to recompile kernels or bug driver authors or wait twelve
> months. 

It's *one* usage of Linux. For this usage, you could also suggest to stop
supporting UP kernels and always build everything with SMP enabled since
more and more often, people will use multi-core systems. It will exempt
the users from upgrading their kernels when they replace their CPU. We
could also try to chase down all the drivers which do not correctly behave
when the CPU switches to a lower frequency.

> And it means that doing a bare minimum isn't enough. We keep claiming
> that Open Source is better than Proprietary software. If we accept
> half-pie jobs of implementing support for anything - driver power
> management support or hibernation support or whatever - as 'good
> enough', we're undercutting that argument. Linux's power management
> support should - as far as we're able - be at least as good as that
> other operating system's and preferably way, way better.
> 
> -ENOSYS is just not acceptable.

Nigel, don't take it as a personal offense, but I think it is a very
centric view of Linux usages. Where I work, Linux is used a lot on
servers and appliances. It is used for mail relays, HTTP proxies,
anti-viruses, firewalls, routers, load balancers, UTM, SSH relays,
etc... Nobody would ever want to enable power management on those
machines, let alone suspend which would cause a major havoc, would
the system decide to enter suspend for any reason.

Many people also have Linux on their notebooks, but as a dual-boot. You
read the word ? "dual-boot". It means that they cleanly shutdown their
system every time they don't use it anymore, and they won't know what
OS they'll use next time.

I've never heard anyone there complaining "oh, I'm fed up with this
boring boot, I always have to wait 30 seconds when I need to do
something, I wish I could suspend and resume". It is considered the
normal way of using their PCs.

So globally, those hundreds of notebooks, workstations and servers
will not be customers of the suspend code any time soon. It would
be a shame to deprive them from working drivers. You must just
accept that a lot of people are not interested in your work. It's
the same for all of us here. I know that a lot of people are not
interested in 2.4 anymore and I'm perfectly fine with that. I'm
not asking 2.6 driver authors to ensure that their driver is easy
to backport for instance.

What I really think would be a clean solution would be sort of
a capability. Either the driver *is* suspend/resume-capable, and
the system can be suspended. Or it is not, and the system must
refuse to suspend. It should not be a problem to proceed like
this because drivers which will not support suspend will mainly
be those which will not have to. And if a user occasionnaly
complains that one driver does not support it, at least you will
have a good argument against its author to implement suspend.

Best regards,
Willy

Re: NAK new drivers without proper power management?

[Rafael J. Wysocki]

On Sunday, 11 February 2007 07:46, Willy Tarreau wrote:
[--snip--]

> What I really think would be a clean solution would be sort of
> a capability. Either the driver *is* suspend/resume-capable, and
> the system can be suspended. Or it is not, and the system must
> refuse to suspend. It should not be a problem to proceed like
> this because drivers which will not support suspend will mainly
> be those which will not have to. And if a user occasionnaly
> complains that one driver does not support it, at least you will
> have a good argument against its author to implement suspend.

I agree, but the suspend/resume safeness has to be somehow indicated by
the driver.  We could add a flag for that, but it would require us to modify
lots of existing drivers (unless there's something obvious I don't see).
However, the driver can effectively say "I'm not suspend/resume-safe" by
returning an error from .suspend(), in which case the system will automatically
refuse to suspend.

Greetings,
Rafael

Re: NAK new drivers without proper power management?

[Nigel Cunningham]

Hi.

On Sun, 2007-02-11 at 07:46 +0100, Willy Tarreau wrote:
> Hi Nigel,
> 
> On Sun, Feb 11, 2007 at 09:37:06AM +1100, Nigel Cunningham wrote:
> > On Sat, 2007-02-10 at 23:20 +0100, Rafael J. Wysocki wrote:
> (...)
> > > What about this:
> > > 
> > > "If the device requires that, implement .suspend and .resume or at least
> > > define .suspend that will always return -ENOSYS (then people will know they
> > > have to unload the driver before the suspend).  Similarly, if you aren't sure
> > > whether or not the device requires .suspend and .resume, define .suspend that
> > > will always return -ENOSYS."
> > 
> > If your device requires power management, and you know it requires power
> > management, why not just implement power management? Doing -ENOSYS
> > instead is like saying -ESPAMMEBECAUSEIMLAZY.
> 
> No, it means "Not implemented because I don't want to screw that driver with
> something I'm not expert in". And it also means "Other people will quickly
> notice it and will know how to fix this if they really need it".

Ok, that was a bit rough. Sorry.

At the same time though, we were talking about new drivers. If you know
enough to implement the rest of the driver, surely you know enough to
implement the power management part too. (See my previous comment about
the similarities to module load/unload code).

> > Let me put it another way: People keep talking about Linux being ready
> > for the desktop. To me at least (but I dare say for lots of other people
> > too), being ready for the desktop means that things just work, without
> > having to recompile kernels or bug driver authors or wait twelve
> > months. 
> 
> It's *one* usage of Linux. For this usage, you could also suggest to stop
> supporting UP kernels and always build everything with SMP enabled since
> more and more often, people will use multi-core systems. It will exempt
> the users from upgrading their kernels when they replace their CPU. We
> could also try to chase down all the drivers which do not correctly behave
> when the CPU switches to a lower frequency.
> 
> > And it means that doing a bare minimum isn't enough. We keep claiming
> > that Open Source is better than Proprietary software. If we accept
> > half-pie jobs of implementing support for anything - driver power
> > management support or hibernation support or whatever - as 'good
> > enough', we're undercutting that argument. Linux's power management
> > support should - as far as we're able - be at least as good as that
> > other operating system's and preferably way, way better.
> > 
> > -ENOSYS is just not acceptable.
> 
> Nigel, don't take it as a personal offense, but I think it is a very
> centric view of Linux usages. Where I work, Linux is used a lot on
> servers and appliances. It is used for mail relays, HTTP proxies,
> anti-viruses, firewalls, routers, load balancers, UTM, SSH relays,
> etc... Nobody would ever want to enable power management on those
> machines, let alone suspend which would cause a major havoc, would
> the system decide to enter suspend for any reason.

I agree.

> Many people also have Linux on their notebooks, but as a dual-boot. You
> read the word ? "dual-boot". It means that they cleanly shutdown their
> system every time they don't use it anymore, and they won't know what
> OS they'll use next time.

Not necessarily. I dual boot our desktop machine, and hibernate both,
using grub to select with OS to run.

> I've never heard anyone there complaining "oh, I'm fed up with this
> boring boot, I always have to wait 30 seconds when I need to do
> something, I wish I could suspend and resume". It is considered the
> normal way of using their PCs.
> 
> So globally, those hundreds of notebooks, workstations and servers
> will not be customers of the suspend code any time soon. It would
> be a shame to deprive them from working drivers. You must just
> accept that a lot of people are not interested in your work. It's
> the same for all of us here. I know that a lot of people are not
> interested in 2.4 anymore and I'm perfectly fine with that. I'm
> not asking 2.6 driver authors to ensure that their driver is easy
> to backport for instance.

Neither am I. I'm just asking that new drivers have power management as
standard.

> What I really think would be a clean solution would be sort of
> a capability. Either the driver *is* suspend/resume-capable, and
> the system can be suspended. Or it is not, and the system must
> refuse to suspend. It should not be a problem to proceed like
> this because drivers which will not support suspend will mainly
> be those which will not have to. And if a user occasionnaly
> complains that one driver does not support it, at least you will
> have a good argument against its author to implement suspend.

Yes, but why should the user have to complain to start with?

Regards,

Nigel

Re: NAK new drivers without proper power management?

[Manu Abraham]

On 2/12/07, Nigel Cunningham <nigel@nigel.suspend2.net> wrote:

> Neither am I. I'm just asking that new drivers have power management as
> standard.


What if the hardware doesn't support power management ?

regards,
manu

Re: NAK new drivers without proper power management?

[Nigel Cunningham]

Hi.

On Mon, 2007-02-12 at 02:57 +0400, Manu Abraham wrote:
> On 2/12/07, Nigel Cunningham <nigel@nigel.suspend2.net> wrote:
> 
> > Neither am I. I'm just asking that new drivers have power management as
> > standard.

> What if the hardware doesn't support power management ?

You would still want to do the cleanup and configuration that you'd do
for module load/unload.

Regards,

Nigel

Re: NAK new drivers without proper power management?

[Manu Abraham]

On 2/12/07, Nigel Cunningham <nigel@nigel.suspend2.net> wrote:
> Hi.
>
> On Mon, 2007-02-12 at 02:57 +0400, Manu Abraham wrote:
> > On 2/12/07, Nigel Cunningham <nigel@nigel.suspend2.net> wrote:
> >
> > > Neither am I. I'm just asking that new drivers have power management as
> > > standard.
>
> > What if the hardware doesn't support power management ?
>
> You would still want to do the cleanup and configuration that you'd do
> for module load/unload.
>

By adding dummy functions, wouldn't that just look awkward ?

regards,
manu

Re: NAK new drivers without proper power management?

[Pavel Machek]

Hi!

> >> > Neither am I. I'm just asking that new drivers have power management as
> >> > standard.
> >
> >> What if the hardware doesn't support power management ?
> >
> >You would still want to do the cleanup and configuration that you'd do
> >for module load/unload.
> >
> 
> By adding dummy functions, wouldn't that just look awkward ?

No, it is not by dummy functions. Checkout how swsusp works; it needs
no hw support, still it needs driver support.

									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

Re: NAK new drivers without proper power management?

[Nigel Cunningham]

Hi.

On Mon, 2007-02-12 at 03:25 +0400, Manu Abraham wrote:
> On 2/12/07, Nigel Cunningham <nigel@nigel.suspend2.net> wrote:
> > Hi.
> >
> > On Mon, 2007-02-12 at 02:57 +0400, Manu Abraham wrote:
> > > On 2/12/07, Nigel Cunningham <nigel@nigel.suspend2.net> wrote:
> > >
> > > > Neither am I. I'm just asking that new drivers have power management as
> > > > standard.
> >
> > > What if the hardware doesn't support power management ?
> >
> > You would still want to do the cleanup and configuration that you'd do
> > for module load/unload.
> >
> By adding dummy functions, wouldn't that just look awkward ?

If all you need to do is say 'I don't need to do anything' and we have a
shared function that does that, all we're talking about doing is adding
to your struct pci_device (or whatever)

.resume = generic_empty_resume;

To me at least, that doesn't look awkward, and says cleanly and clearly
that you've checked things over and decided you know what's required.

Regards,

Nigel

Re: NAK new drivers without proper power management?

[Pavel Machek]

Hi!

> > > > > Neither am I. I'm just asking that new drivers have power management as
> > > > > standard.
> > >
> > > > What if the hardware doesn't support power management ?
> > >
> > > You would still want to do the cleanup and configuration that you'd do
> > > for module load/unload.
> > >
> > By adding dummy functions, wouldn't that just look awkward ?
> 
> If all you need to do is say 'I don't need to do anything' and we have a
> shared function that does that, all we're talking about doing is adding
> to your struct pci_device (or whatever)
> 
> .resume = generic_empty_resume;
> 
> To me at least, that doesn't look awkward, and says cleanly and clearly
> that you've checked things over and decided you know what's required.

Actually, I'd like it to be

.resume = generic_empty_resume; /* Explain, why your driver needs no
				   resume */

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

Re: NAK new drivers without proper power management?

[Rafael J. Wysocki]

On Monday, 12 February 2007 17:52, Pavel Machek wrote:
> Hi!
> 
> > > > > > Neither am I. I'm just asking that new drivers have power management as
> > > > > > standard.
> > > >
> > > > > What if the hardware doesn't support power management ?
> > > >
> > > > You would still want to do the cleanup and configuration that you'd do
> > > > for module load/unload.
> > > >
> > > By adding dummy functions, wouldn't that just look awkward ?
> > 
> > If all you need to do is say 'I don't need to do anything' and we have a
> > shared function that does that, all we're talking about doing is adding
> > to your struct pci_device (or whatever)
> > 
> > .resume = generic_empty_resume;
> > 
> > To me at least, that doesn't look awkward, and says cleanly and clearly
> > that you've checked things over and decided you know what's required.
> 
> Actually, I'd like it to be
> 
> .resume = generic_empty_resume; /* Explain, why your driver needs no
> 				   resume */

Okay, but we can't define an empty .resume(), because, for example, the PCI's
generic suspend/resume won't be called.

I think we can introduce a "pm_safe" flag that will indicate if the driver
handles suspend/resume correctly.  If we do it, we can flag all of the drivers
currently in the tree as "pm_safe" unless we know that they aren't.  Next,
we can convert the core to fail the suspend for any driver that is not flagged
as "pm_safe".  But I think that will take time.

In the meantime, I'd like to ask the authors of new drivers to define
error-returning .suspend() if they don't intend to define "real" .suspend()
and .resume() for now.  When we are ready with the conversion, we'll be able
to drop the error-returning .suspend()s and clear "pm_safe" for them.

Greetings,
Rafael

Re: NAK new drivers without proper power management?

[Pavel Machek]

Hi!

> > > If all you need to do is say 'I don't need to do anything' and we have a
> > > shared function that does that, all we're talking about doing is adding
> > > to your struct pci_device (or whatever)
> > > 
> > > .resume = generic_empty_resume;
> > > 
> > > To me at least, that doesn't look awkward, and says cleanly and clearly
> > > that you've checked things over and decided you know what's required.
> > 
> > Actually, I'd like it to be
> > 
> > .resume = generic_empty_resume; /* Explain, why your driver needs no
> > 				   resume */
> 
> Okay, but we can't define an empty .resume(), because, for example, the PCI's
> generic suspend/resume won't be called.

PCI drivers should just do .resume = pci_generic_resume, explicitely.

> In the meantime, I'd like to ask the authors of new drivers to define
> error-returning .suspend() if they don't intend to define "real" .suspend()
> and .resume() for now.  When we are ready with the conversion, we'll be able
> to drop the error-returning .suspend()s and clear "pm_safe" for them.

Yes... please.
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

Re: NAK new drivers without proper power management?

[Rafael J. Wysocki]

On Monday, 12 February 2007 21:58, Pavel Machek wrote:
> Hi!
> 
> > > > If all you need to do is say 'I don't need to do anything' and we have a
> > > > shared function that does that, all we're talking about doing is adding
> > > > to your struct pci_device (or whatever)
> > > > 
> > > > .resume = generic_empty_resume;
> > > > 
> > > > To me at least, that doesn't look awkward, and says cleanly and clearly
> > > > that you've checked things over and decided you know what's required.
> > > 
> > > Actually, I'd like it to be
> > > 
> > > .resume = generic_empty_resume; /* Explain, why your driver needs no
> > > 				   resume */
> > 
> > Okay, but we can't define an empty .resume(), because, for example, the PCI's
> > generic suspend/resume won't be called.
> 
> PCI drivers should just do .resume = pci_generic_resume, explicitely.

Well, I generally agree, but I think the idea with the "pm_safe" flag has some
advantages.  For example, the drivers that do deffine .suspend() and .resume()
which don't work correctly could be flagged as not "pm_safe" until the problems
are fixed.

Greetings,
Rafael

Re: NAK new drivers without proper power management?

[Nigel Cunningham]

Hi.

On Mon, 2007-02-12 at 22:01 +0100, Rafael J. Wysocki wrote:
> On Monday, 12 February 2007 21:58, Pavel Machek wrote:
> > Hi!
> > 
> > > > > If all you need to do is say 'I don't need to do anything' and we have a
> > > > > shared function that does that, all we're talking about doing is adding
> > > > > to your struct pci_device (or whatever)
> > > > > 
> > > > > .resume = generic_empty_resume;
> > > > > 
> > > > > To me at least, that doesn't look awkward, and says cleanly and clearly
> > > > > that you've checked things over and decided you know what's required.
> > > > 
> > > > Actually, I'd like it to be
> > > > 
> > > > .resume = generic_empty_resume; /* Explain, why your driver needs no
> > > > 				   resume */
> > > 
> > > Okay, but we can't define an empty .resume(), because, for example, the PCI's
> > > generic suspend/resume won't be called.
> > 
> > PCI drivers should just do .resume = pci_generic_resume, explicitely.
> 
> Well, I generally agree, but I think the idea with the "pm_safe" flag has some
> advantages.  For example, the drivers that do deffine .suspend() and .resume()
> which don't work correctly could be flagged as not "pm_safe" until the problems
> are fixed.

Oooh. Now I like that idea. Are you thinking of a document in
Documentation/power that describes why pm_safe is off, or comments in
the code itself?

Regards,

Nigel

Re: NAK new drivers without proper power management?

[Rafael J. Wysocki]

On Monday, 12 February 2007 22:24, Nigel Cunningham wrote:
> Hi.
> 
> On Mon, 2007-02-12 at 22:01 +0100, Rafael J. Wysocki wrote:
> > On Monday, 12 February 2007 21:58, Pavel Machek wrote:
> > > Hi!
> > > 
> > > > > > If all you need to do is say 'I don't need to do anything' and we have a
> > > > > > shared function that does that, all we're talking about doing is adding
> > > > > > to your struct pci_device (or whatever)
> > > > > > 
> > > > > > .resume = generic_empty_resume;
> > > > > > 
> > > > > > To me at least, that doesn't look awkward, and says cleanly and clearly
> > > > > > that you've checked things over and decided you know what's required.
> > > > > 
> > > > > Actually, I'd like it to be
> > > > > 
> > > > > .resume = generic_empty_resume; /* Explain, why your driver needs no
> > > > > 				   resume */
> > > > 
> > > > Okay, but we can't define an empty .resume(), because, for example, the PCI's
> > > > generic suspend/resume won't be called.
> > > 
> > > PCI drivers should just do .resume = pci_generic_resume, explicitely.
> > 
> > Well, I generally agree, but I think the idea with the "pm_safe" flag has some
> > advantages.  For example, the drivers that do define .suspend() and .resume()
> > which don't work correctly could be flagged as not "pm_safe" until the problems
> > are fixed.
> 
> Oooh. Now I like that idea. Are you thinking of a document in
> Documentation/power that describes why pm_safe is off, or comments in
> the code itself?

I think the code should be commented in the first place.  Additionally, we can
create a file or a directory under Documentation/power for documenting more
complicated cases, if necessary.

Greetings,
Rafael

Re: NAK new drivers without proper power management?

[Tilman Schmidt]

[-- Attachment #1: Type: text/plain, Size: 1440 bytes --]

Rafael J. Wysocki schrieb:
> I think we can introduce a "pm_safe" flag that will indicate if the driver
> handles suspend/resume correctly.  If we do it, we can flag all of the drivers
> currently in the tree as "pm_safe" unless we know that they aren't.  Next,
> we can convert the core to fail the suspend for any driver that is not flagged
> as "pm_safe".  But I think that will take time.

Why a new flag? IMHO it would be both more readable and more efficient
to create a pm_generic_nosuspend() function which does "return -ENOSYS",
and set that as the .suspend method on drivers known to break
suspend/resume. New drivers should either have .suspend and .resume
methods of their own or set .suspend = pm_generic_nosuspend.

That way, NULL .suspend/.resume methods retain their current semantics
("don't know whether suspend would work, never thought about it"),
error-returning ones would clearly signal "cannot suspend safely", and
success-returning ones would equally clearly signal "suspend works ok".
(Bugs nonwithstanding.)

There could then be a policy parameter (Kconfig selectable to start)
to abort suspend when encountering a driver without .suspend/.resume
methods, or to proceed with a warning message.

-- 
Tilman Schmidt                    E-Mail: tilman@imap.cc
Bonn, Germany
Diese Nachricht besteht zu 100% aus wiederverwerteten Bits.
Ungeöffnet mindestens haltbar bis: (siehe Rückseite)


[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 250 bytes --]

Re: NAK new drivers without proper power management?

[Rafael J. Wysocki]

On Tuesday, 13 February 2007 10:42, Tilman Schmidt wrote:
> Rafael J. Wysocki schrieb:
> > I think we can introduce a "pm_safe" flag that will indicate if the driver
> > handles suspend/resume correctly.  If we do it, we can flag all of the drivers
> > currently in the tree as "pm_safe" unless we know that they aren't.  Next,
> > we can convert the core to fail the suspend for any driver that is not flagged
> > as "pm_safe".  But I think that will take time.
> 
> Why a new flag?

For example, there are drivers that define .suspend() and .resume() which
do not work correctly and we can use the flag to mark them.

> IMHO it would be both more readable and more efficient 
> to create a pm_generic_nosuspend() function which does "return -ENOSYS",
> and set that as the .suspend method on drivers known to break
> suspend/resume. New drivers should either have .suspend and .resume
> methods of their own or set .suspend = pm_generic_nosuspend.

This is quite similar to what we are trying to do now: ask driver authors to
define .suspend that will return -ENOSYS if they can't ensure that the driver
will handle the suspend and resume correctly.

> That way, NULL .suspend/.resume methods retain their current semantics
> ("don't know whether suspend would work, never thought about it"),

I think this convention is unfortunate.  The default should be to fail the
suspend if there's no .suspend defined, IMO.  Still, it's hard to change now.

> error-returning ones would clearly signal "cannot suspend safely", and
> success-returning ones would equally clearly signal "suspend works ok".
> (Bugs nonwithstanding.)
> 
> There could then be a policy parameter (Kconfig selectable to start)
> to abort suspend when encountering a driver without .suspend/.resume
> methods, or to proceed with a warning message.

I think there are many drivers without .suspend and .resume already in the
tree, so that wouldn't be practical.

Greetings,
Rafael

Re: NAK new drivers without proper power management?

[Stefan Richter]

Rafael J. Wysocki wrote:
>> Why a new flag?
> 
> For example, there are drivers that define .suspend() and .resume() which
> do not work correctly and we can use the flag to mark them.

Depending on how serious the problems with these .suspend/.resume()s
are, you could also put a printk in them or #if 0 bad_code #else return
-ENOSYS #endif around them.

Re: NAK new drivers without proper power management?

[Arjan van de Ven]

> 
> By adding dummy functions, wouldn't that just look awkward ?

not really; if you have a template


pm_no_suspend_needed
and
pm_no_restore_needed

functions, and just make it part of ALL device structs that don't need
it.. it's not that bad

or maybe 

pm_generic_no_suspend
pm_generic_no_resume

as names, more in line what we use elsewhere in the kernel
-- 
if you want to mail me at work (you don't), use arjan (at) linux.intel.com
Test the interaction between Linux and your BIOS via http://www.linuxfirmwarekit.org

Re: NAK new drivers without proper power management?

[Gerhard Mack]

On Sun, 11 Feb 2007, Willy Tarreau wrote:

> On Sun, Feb 11, 2007 at 09:37:06AM +1100, Nigel Cunningham wrote:
> > On Sat, 2007-02-10 at 23:20 +0100, Rafael J. Wysocki wrote:
> 
> Many people also have Linux on their notebooks, but as a dual-boot. You
> read the word ? "dual-boot". It means that they cleanly shutdown their
> system every time they don't use it anymore, and they won't know what
> OS they'll use next time.

Please tell me your joking.  Linux' crappy suspend support is a common 
reason people give me for not wanting Linux anywhere near their laptops.  

I have a single boot laptop that's somewhat of a mobile debugging station 
that needs Linux and I absolutely hate it.  Right now my laptop takes far 
too long to boot and even if it didn't I wish I could suspend.

I'm actually a huge Linux fan.. I use it exclusively on my server and on 
my PC but if I get another laptop I will probably run something else on 
it.  Linux is just too annoying for that use.

	Gerhard



--
Gerhard Mack

gmack@innerfire.net

<>< As a computer I find your faith in technology amusing.

Re: NAK new drivers without proper power management?

[Willy Tarreau]

On Mon, Feb 12, 2007 at 07:59:40AM -0500, Gerhard Mack wrote:
> On Sun, 11 Feb 2007, Willy Tarreau wrote:
> 
> > On Sun, Feb 11, 2007 at 09:37:06AM +1100, Nigel Cunningham wrote:
> > > On Sat, 2007-02-10 at 23:20 +0100, Rafael J. Wysocki wrote:
> > 
> > Many people also have Linux on their notebooks, but as a dual-boot. You
> > read the word ? "dual-boot". It means that they cleanly shutdown their
> > system every time they don't use it anymore, and they won't know what
> > OS they'll use next time.
> 
> Please tell me your joking.  Linux' crappy suspend support is a common 
> reason people give me for not wanting Linux anywhere near their laptops.  

No, I'm not kidding. The most annoyed ones are those who don't have serial
ports and who need those annoying USB adapters. But fortunately, not all
of them need to access router consoles :-)

> I have a single boot laptop that's somewhat of a mobile debugging station 
> that needs Linux and I absolutely hate it.  Right now my laptop takes far 
> too long to boot and even if it didn't I wish I could suspend.

Probably that you got the wrong laptop. If you buy an ultra-thin with highly
proprietary hardware, it may be hard. But if you choose in profesionnal ranges,
there is rarely any problem. I have a compaq nc8000 on which everything works
fine, and it boots in about 20 seconds. Other people I know have Toshibas,
NECs, Dells and IBMs and are happy with them. My previous VAIO was a dirty
crap that I would never recommend to anybody though.

> I'm actually a huge Linux fan.. I use it exclusively on my server and on 
> my PC but if I get another laptop I will probably run something else on 
> it.  Linux is just too annoying for that use.

Everyone has different needs, that's all.

Sorry, but I fell like we're becoming a bit off-topic here.

Regards,
Willy

Re: NAK new drivers without proper power management?

[Brad Campbell]

Willy Tarreau wrote:

> Probably that you got the wrong laptop. If you buy an ultra-thin with highly
> proprietary hardware, it may be hard. But if you choose in profesionnal ranges,
> there is rarely any problem. I have a compaq nc8000 on which everything works
> fine, and it boots in about 20 seconds. Other people I know have Toshibas,
> NECs, Dells and IBMs and are happy with them. My previous VAIO was a dirty
> crap that I would never recommend to anybody though.

Whereas my "ultru-thin" VAIO works perfectly with both S2D and S2R and the only thing I have some 
difficulty with is the SD reader. Would not hesitate to recommend it to anyone.

I often hibernate linux to boot into a hibernated windows session, then go back the other way as 
required, and my machine might do 80-100 "suspend2both" sessions a month between reboots. 30-40 
seconds to suspend mostly (1.5GB of RAM) and about 15 to come back. That's what I call highly useful.

Different strokes and all that I guess..

Brad
-- 
"Human beings, who are almost unique in having the ability
to learn from the experience of others, are also remarkable
for their apparent disinclination to do so." -- Douglas Adams

Re: NAK new drivers without proper power management?

[Rafael J. Wysocki]

On Monday, 12 February 2007 13:59, Gerhard Mack wrote:
> On Sun, 11 Feb 2007, Willy Tarreau wrote:
> 
> > On Sun, Feb 11, 2007 at 09:37:06AM +1100, Nigel Cunningham wrote:
> > > On Sat, 2007-02-10 at 23:20 +0100, Rafael J. Wysocki wrote:
> > 
> > Many people also have Linux on their notebooks, but as a dual-boot. You
> > read the word ? "dual-boot". It means that they cleanly shutdown their
> > system every time they don't use it anymore, and they won't know what
> > OS they'll use next time.
> 
> Please tell me your joking.  Linux' crappy suspend support is a common 
> reason people give me for not wanting Linux anywhere near their laptops.  
> 
> I have a single boot laptop that's somewhat of a mobile debugging station 
> that needs Linux and I absolutely hate it.  Right now my laptop takes far 
> too long to boot and even if it didn't I wish I could suspend.

When did you try last time?

Rafael

Re: NAK new drivers without proper power management?

[Tino Keitel]

On Sun, Feb 11, 2007 at 07:46:36 +0100, Willy Tarreau wrote:

[...]

> Many people also have Linux on their notebooks, but as a dual-boot. You
> read the word ? "dual-boot". It means that they cleanly shutdown their
> system every time they don't use it anymore, and they won't know what
> OS they'll use next time.

I can suspend to disk my Mac mini, reboot into MacOS X, shutdown, and
then resume in Linux. I also did this with APM suspend to disk support
on my ThinkPad some years ago, using Linux and Windows.

So, dualboot and suspend support isn't mutual exclusive. This is only
the case if suspend is limited to suspend to RAM.

Regards,
Tino

Re: NAK new drivers without proper power management?

[Pavel Machek]

Hi!

> > > > Can we start to NAK new drivers that don't have proper power management
> > > > implemented? There really is no excuse for writing a new driver and not
> > > > putting .suspend and .resume methods in anymore, is there?
> > > 
> > > to a large degree, a device driver that doesn't suspend is better than
> > > no device driver at all, right?
> > > now.. if you want to make the core warn about it, that's very fair
> > 
> > Well, driver that is broken on SMP is arguably better than no driver
> > at all, yet we'd probably avoid merging that. It would be nice to
> > start including suspend in 'must work' list...
> 
> What about this:
> 
> "If the device requires that, implement .suspend and .resume or at least
> define .suspend that will always return -ENOSYS (then people will know they
> have to unload the driver before the suspend).  Similarly, if you aren't sure
> whether or not the device requires .suspend and .resume, define .suspend that
> will always return -ENOSYS."

Sounds ok to me. Where should this text go?
Documentation/SubmittingDrivers ?

									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

Re: NAK new drivers without proper power management?

[Alan]

> > "If the device requires that, implement .suspend and .resume or at least
> > define .suspend that will always return -ENOSYS (then people will know they
> > have to unload the driver before the suspend).  Similarly, if you aren't sure
> > whether or not the device requires .suspend and .resume, define .suspend that
> > will always return -ENOSYS."
> 
> Sounds ok to me. Where should this text go?
> Documentation/SubmittingDrivers ?

And testing/submitting drivers, perhaps with additional text in that to
make it clear we want suspend/resume support or good excuses

"Please verify your driver correctly handles suspend and resume. If it
does not your patch submission is likely to be suspended and only resume
when the driver correctly handles this feature"

Re: NAK new drivers without proper power management?

[Rafael J. Wysocki]

On Sunday, 11 February 2007 22:02, Alan wrote:
> > > "If the device requires that, implement .suspend and .resume or at least
> > > define .suspend that will always return -ENOSYS (then people will know they
> > > have to unload the driver before the suspend).  Similarly, if you aren't sure
> > > whether or not the device requires .suspend and .resume, define .suspend that
> > > will always return -ENOSYS."
> > 
> > Sounds ok to me. Where should this text go?
> > Documentation/SubmittingDrivers ?
> 
> And testing/submitting drivers, perhaps with additional text in that to
> make it clear we want suspend/resume support or good excuses
> 
> "Please verify your driver correctly handles suspend and resume. If it
> does not your patch submission is likely to be suspended and only resume
> when the driver correctly handles this feature"

I have prepared a patch against Documentation/SubmittingDrivers.  Please
have a look.

---
 Documentation/SubmittingDrivers |   12 ++++++++++++
 1 file changed, 12 insertions(+)

Index: linux-2.6.20-git4/Documentation/SubmittingDrivers
===================================================================
--- linux-2.6.20-git4.orig/Documentation/SubmittingDrivers
+++ linux-2.6.20-git4/Documentation/SubmittingDrivers
@@ -87,6 +87,18 @@ Clarity:	It helps if anyone can see how 
 		driver that intentionally obfuscates how the hardware works
 		it will go in the bitbucket.
 
+PM support:	Since Linux is used on many portable and desktop systems, your
+		driver is likely to be used on such a system and therefore it
+		should support basic power management by implementing, if
+		necessary, the .suspend and .resume methods used during the
+		system-wide suspend and resume transitions.  You should verify
+		that your driver correctly handles the suspend and resume, but
+		if you are unable to ensure that, please at least define the
+		.suspend method returning the -ENOSYS ("Function not
+		implemented") error.  Note, however, that in such a case your
+		submission is likely to be suspended and only resumed when the
+		driver correctly handles this feature.
+
 Control:	In general if there is active maintainance of a driver by
 		the author then patches will be redirected to them unless
 		they are totally obvious and without need of checking.

Re: NAK new drivers without proper power management?

[Alan]

> +PM support:	Since Linux is used on many portable and desktop systems, your
> +		driver is likely to be used on such a system and therefore it
> +		should support basic power management by implementing, if
> +		necessary, the .suspend and .resume methods used during the
> +		system-wide suspend and resume transitions.  You should verify
> +		that your driver correctly handles the suspend and resume, but
> +		if you are unable to ensure that, please at least define the
> +		.suspend method returning the -ENOSYS ("Function not
> +		implemented") error.  Note, however, that in such a case your
> +		submission is likely to be suspended and only resumed when the
> +		driver correctly handles this feature.

I'd lose the last bit. Just end it at "error.", there are going to be
people who produce good reasons not to handle suspend/resume.

Re: NAK new drivers without proper power management?

[Rafael J. Wysocki]

On Monday, 12 February 2007 01:28, Alan wrote:
> > +PM support:	Since Linux is used on many portable and desktop systems, your
> > +		driver is likely to be used on such a system and therefore it
> > +		should support basic power management by implementing, if
> > +		necessary, the .suspend and .resume methods used during the
> > +		system-wide suspend and resume transitions.  You should verify
> > +		that your driver correctly handles the suspend and resume, but
> > +		if you are unable to ensure that, please at least define the
> > +		.suspend method returning the -ENOSYS ("Function not
> > +		implemented") error.  Note, however, that in such a case your
> > +		submission is likely to be suspended and only resumed when the
> > +		driver correctly handles this feature.
> 
> I'd lose the last bit. Just end it at "error.", there are going to be
> people who produce good reasons not to handle suspend/resume.

OK, I will.

Re: NAK new drivers without proper power management?

[Nigel Cunningham]

Hi.

On Sun, 2007-02-11 at 21:02 +0000, Alan wrote:
> > > "If the device requires that, implement .suspend and .resume or at least
> > > define .suspend that will always return -ENOSYS (then people will know they
> > > have to unload the driver before the suspend).  Similarly, if you aren't sure
> > > whether or not the device requires .suspend and .resume, define .suspend that
> > > will always return -ENOSYS."
> > 
> > Sounds ok to me. Where should this text go?
> > Documentation/SubmittingDrivers ?
> 
> And testing/submitting drivers, perhaps with additional text in that to
> make it clear we want suspend/resume support or good excuses
> 
> "Please verify your driver correctly handles suspend and resume. If it
> does not your patch submission is likely to be suspended and only resume
> when the driver correctly handles this feature"

Maybe make it explicit that testing should be done for both suspend to
ram and to disk, and with the following usage scenarios as applicable?

- built in;
- modular, loaded while suspending but not loaded prior to resume from
disk;
- modular, loaded while suspending and loaded prior to resume from disk;

Regards,

Nigel

Re: NAK new drivers without proper power management?

[Rafael J. Wysocki]

On Monday, 12 February 2007 00:10, Nigel Cunningham wrote:
> Hi.
> 
> On Sun, 2007-02-11 at 21:02 +0000, Alan wrote:
> > > > "If the device requires that, implement .suspend and .resume or at least
> > > > define .suspend that will always return -ENOSYS (then people will know they
> > > > have to unload the driver before the suspend).  Similarly, if you aren't sure
> > > > whether or not the device requires .suspend and .resume, define .suspend that
> > > > will always return -ENOSYS."
> > > 
> > > Sounds ok to me. Where should this text go?
> > > Documentation/SubmittingDrivers ?
> > 
> > And testing/submitting drivers, perhaps with additional text in that to
> > make it clear we want suspend/resume support or good excuses
> > 
> > "Please verify your driver correctly handles suspend and resume. If it
> > does not your patch submission is likely to be suspended and only resume
> > when the driver correctly handles this feature"
> 
> Maybe make it explicit that testing should be done for both suspend to
> ram and to disk, and with the following usage scenarios as applicable?
> 
> - built in;
> - modular, loaded while suspending but not loaded prior to resume from
> disk;
> - modular, loaded while suspending and loaded prior to resume from disk;

I think we should state the general rule in Documentation/SubmittingDrivers
and give more details in Documentation/power/devices.txt

Greetings,
Rafael

Re: NAK new drivers without proper power management?

[Nigel Cunningham]

Hi.

On Mon, 2007-02-12 at 00:16 +0100, Rafael J. Wysocki wrote:
> On Monday, 12 February 2007 00:10, Nigel Cunningham wrote:
> > Hi.
> > 
> > On Sun, 2007-02-11 at 21:02 +0000, Alan wrote:
> > > > > "If the device requires that, implement .suspend and .resume or at least
> > > > > define .suspend that will always return -ENOSYS (then people will know they
> > > > > have to unload the driver before the suspend).  Similarly, if you aren't sure
> > > > > whether or not the device requires .suspend and .resume, define .suspend that
> > > > > will always return -ENOSYS."
> > > > 
> > > > Sounds ok to me. Where should this text go?
> > > > Documentation/SubmittingDrivers ?
> > > 
> > > And testing/submitting drivers, perhaps with additional text in that to
> > > make it clear we want suspend/resume support or good excuses
> > > 
> > > "Please verify your driver correctly handles suspend and resume. If it
> > > does not your patch submission is likely to be suspended and only resume
> > > when the driver correctly handles this feature"
> > 
> > Maybe make it explicit that testing should be done for both suspend to
> > ram and to disk, and with the following usage scenarios as applicable?
> > 
> > - built in;
> > - modular, loaded while suspending but not loaded prior to resume from
> > disk;
> > - modular, loaded while suspending and loaded prior to resume from disk;
> 
> I think we should state the general rule in Documentation/SubmittingDrivers
> and give more details in Documentation/power/devices.txt

Sounds good.

Regards,

Nigel

Re: NAK new drivers without proper power management?

[Pavel Machek]

Hi!

> > > - built in;
> > > - modular, loaded while suspending but not loaded prior to resume from
> > > disk;
> > > - modular, loaded while suspending and loaded prior to resume from disk;
> > 
> > I think we should state the general rule in Documentation/SubmittingDrivers
> > and give more details in Documentation/power/devices.txt
> 
> Sounds good.

Ok, so who does the patch?
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

Re: NAK new drivers without proper power management?

[Pavel Machek]

Hi!

> > > > define .suspend that will always return -ENOSYS (then people will know they
> > > > have to unload the driver before the suspend).  Similarly, if you aren't sure
> > > > whether or not the device requires .suspend and .resume, define .suspend that
> > > > will always return -ENOSYS."
> > > 
> > > Sounds ok to me. Where should this text go?
> > > Documentation/SubmittingDrivers ?
> > 
> > And testing/submitting drivers, perhaps with additional text in that to
> > make it clear we want suspend/resume support or good excuses
> > 
> > "Please verify your driver correctly handles suspend and resume. If it
> > does not your patch submission is likely to be suspended and only resume
> > when the driver correctly handles this feature"
> 
> Maybe make it explicit that testing should be done for both suspend to
> ram and to disk, and with the following usage scenarios as
 > applicable?

Well, for many people s2ram does not work even today... so requiring
them to test it is slightly draconian.

> - built in;
> - modular, loaded while suspending but not loaded prior to resume from
> disk;

These two should be equivalent.

> - modular, loaded while suspending and loaded prior to resume from disk;

Ok.. but I'm not sure how many people will actually test it _that_
thoroughly. "Try to test it" is good enough for a first version. When
suspend is in better shape, we can ask for more.

									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

Re: NAK new drivers without proper power management?

[Nigel Cunningham]

Hi.

On Mon, 2007-02-12 at 00:21 +0100, Pavel Machek wrote:
> Hi!
> 
> > > > > define .suspend that will always return -ENOSYS (then people will know they
> > > > > have to unload the driver before the suspend).  Similarly, if you aren't sure
> > > > > whether or not the device requires .suspend and .resume, define .suspend that
> > > > > will always return -ENOSYS."
> > > > 
> > > > Sounds ok to me. Where should this text go?
> > > > Documentation/SubmittingDrivers ?
> > > 
> > > And testing/submitting drivers, perhaps with additional text in that to
> > > make it clear we want suspend/resume support or good excuses
> > > 
> > > "Please verify your driver correctly handles suspend and resume. If it
> > > does not your patch submission is likely to be suspended and only resume
> > > when the driver correctly handles this feature"
> > 
> > Maybe make it explicit that testing should be done for both suspend to
> > ram and to disk, and with the following usage scenarios as
>  > applicable?
> 
> Well, for many people s2ram does not work even today... so requiring
> them to test it is slightly draconian.
> 
> > - built in;
> > - modular, loaded while suspending but not loaded prior to resume from
> > disk;
> 
> These two should be equivalent.

No. The differences are:

Built in: The initcalls will have run, but the driver may or may not
actually have been used, depending on whether it's used before we start
the resume. It should probably be tested with both having been used and
not having been used.
Modular, loaded prior to suspending but not prior to resuming: At resume
time, will still be in whatever config the bios puts it in. No Linux
driver code will have touched it.
Modular, loaded prior to suspending and resuming: Should be equivalent
to built in (module initcalls will have run), but may vary if there's
some difference in code/timing between being a module and built in.
(This shouldn't happen, but that's the point to testing).

> > - modular, loaded while suspending and loaded prior to resume from disk;
> 
> Ok.. but I'm not sure how many people will actually test it _that_
> thoroughly. "Try to test it" is good enough for a first version. When
> suspend is in better shape, we can ask for more.

I'd prefer to ask for what should be done from the start. Will we expect
people to go back and retest if we change the rules, or do we prefer
them to complain "You didn't adequately point out the testing I needed
to do, and I got all these complaints from my users!"

Regards,

Nigel

Re: NAK new drivers without proper power management?

[Tilman Schmidt]

[-- Attachment #1: Type: text/plain, Size: 735 bytes --]

Am 11.02.2007 20:42 schrieb Pavel Machek:
[...]
>> What about this:
>>
>> "If the device requires that, implement .suspend and .resume or at least
>> define .suspend that will always return -ENOSYS (then people will know they
>> have to unload the driver before the suspend).  Similarly, if you aren't sure
>> whether or not the device requires .suspend and .resume, define .suspend that
>> will always return -ENOSYS."
> 
> Sounds ok to me. Where should this text go?
> Documentation/SubmittingDrivers ?


Documentation/power/devices.txt?

-- 
Tilman Schmidt                          E-Mail: tilman@imap.cc
Bonn, Germany
- In theory, there is no difference between theory and practice.
  In practice, there is.


[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 253 bytes --]

Re: NAK new drivers without proper power management?

[Geert Uytterhoeven]

On Sat, 10 Feb 2007, Rafael J. Wysocki wrote:
> What about this:
> 
> "If the device requires that, implement .suspend and .resume or at least
                                                                  ^^^^^^^^
> define .suspend that will always return -ENOSYS (then people will know they
  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> have to unload the driver before the suspend).  Similarly, if you aren't sure
> whether or not the device requires .suspend and .resume, define .suspend that
                                                           ^^^^^^^^^^^^^^^^^^^^
> will always return -ENOSYS."
  ^^^^^^^^^^^^^^^^^^^^^^^^^^^
Can't the upper layer just assume -ENOSYS if .resume/.suspend is NULL?
It's nicer if you don't have to implement dummy functions at all.

Gr{oetje,eeting}s,

						Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
							    -- Linus Torvalds

Re: NAK new drivers without proper power management?

[Pavel Machek]

Hi!

> > "If the device requires that, implement .suspend and .resume or at least
>                                                                   ^^^^^^^^
> > define .suspend that will always return -ENOSYS (then people will know they
>   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> > have to unload the driver before the suspend).  Similarly, if you aren't sure
> > whether or not the device requires .suspend and .resume, define .suspend that
>                                                            ^^^^^^^^^^^^^^^^^^^^
> > will always return -ENOSYS."
>   ^^^^^^^^^^^^^^^^^^^^^^^^^^^
> Can't the upper layer just assume -ENOSYS if .resume/.suspend is NULL?
> It's nicer if you don't have to implement dummy functions at all.

Unfortunately, drivers currently assume "NULL == nothing is needed",
so we'd have t do big search & replace... 
								Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

Re: NAK new drivers without proper power management?

[Geert Uytterhoeven]

On Mon, 12 Feb 2007, Pavel Machek wrote:
> > > "If the device requires that, implement .suspend and .resume or at least
> >                                                                   ^^^^^^^^
> > > define .suspend that will always return -ENOSYS (then people will know they
> >   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> > > have to unload the driver before the suspend).  Similarly, if you aren't sure
> > > whether or not the device requires .suspend and .resume, define .suspend that
> >                                                            ^^^^^^^^^^^^^^^^^^^^
> > > will always return -ENOSYS."
> >   ^^^^^^^^^^^^^^^^^^^^^^^^^^^
> > Can't the upper layer just assume -ENOSYS if .resume/.suspend is NULL?
> > It's nicer if you don't have to implement dummy functions at all.
> 
> Unfortunately, drivers currently assume "NULL == nothing is needed",
> so we'd have t do big search & replace... 

Which means you also cannot easily keep track of which driver supports
suspend/resume and which doesn't, as there will always be drivers where a
missing suspend/resume function is correct.

Wouldn't it be more sensible to have

    .suspend = suspend_nothing_to_do

instead, and reserve NULL for `not yet implemented'?

Gr{oetje,eeting}s,

						Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
							    -- Linus Torvalds

Re: NAK new drivers without proper power management?

[Pavel Machek]

Hi!

> > > > "If the device requires that, implement .suspend and .resume or at least
> > >                                                                   ^^^^^^^^
> > > > define .suspend that will always return -ENOSYS (then people will know they
> > >   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> > > > have to unload the driver before the suspend).  Similarly, if you aren't sure
> > > > whether or not the device requires .suspend and .resume, define .suspend that
> > >                                                            ^^^^^^^^^^^^^^^^^^^^
> > > > will always return -ENOSYS."
> > >   ^^^^^^^^^^^^^^^^^^^^^^^^^^^
> > > Can't the upper layer just assume -ENOSYS if .resume/.suspend is NULL?
> > > It's nicer if you don't have to implement dummy functions at all.
> > 
> > Unfortunately, drivers currently assume "NULL == nothing is needed",
> > so we'd have t do big search & replace... 
> 
> Which means you also cannot easily keep track of which driver supports
> suspend/resume and which doesn't, as there will always be drivers where a
> missing suspend/resume function is correct.
> 
> Wouldn't it be more sensible to have
> 
>     .suspend = suspend_nothing_to_do
> 
> instead, and reserve NULL for `not yet implemented'?

It would be. Patch would be welcome :-).
								Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

Re: NAK new drivers without proper power management?

[Nigel Cunningham]

Hi.

On Mon, 2007-02-12 at 16:57 +0100, Geert Uytterhoeven wrote:
> On Mon, 12 Feb 2007, Pavel Machek wrote:
> > > Can't the upper layer just assume -ENOSYS if .resume/.suspend is NULL?
> > > It's nicer if you don't have to implement dummy functions at all.
> > 
> > Unfortunately, drivers currently assume "NULL == nothing is needed",
> > so we'd have t do big search & replace... 
> 
> Which means you also cannot easily keep track of which driver supports
> suspend/resume and which doesn't, as there will always be drivers where a
> missing suspend/resume function is correct.
> 
> Wouldn't it be more sensible to have
> 
>     .suspend = suspend_nothing_to_do
> 
> instead, and reserve NULL for `not yet implemented'?

Agreed.

Regards,

Nigel

Re: NAK new drivers without proper power management?

[Tilman Schmidt]

[-- Attachment #1: Type: text/plain, Size: 1200 bytes --]

Geert Uytterhoeven schrieb:
> On Mon, 12 Feb 2007, Pavel Machek wrote:

>> > Can't the upper layer just assume -ENOSYS if .resume/.suspend is NULL?
>> > It's nicer if you don't have to implement dummy functions at all.
>> 
>> Unfortunately, drivers currently assume "NULL == nothing is needed",

More often than not they assume nothing of the kind.

>> so we'd have t do big search & replace... 
> 
> Which means you also cannot easily keep track of which driver supports
> suspend/resume and which doesn't, as there will always be drivers where a
> missing suspend/resume function is correct.

I think those are rare exceptions. They could and should be
asked to make this statement explicit, as you propose:

> Wouldn't it be more sensible to have
> 
>     .suspend = suspend_nothing_to_do
> 
> instead, and reserve NULL for `not yet implemented'?

NULL is already taken for 'don't know'. So *two* new values
are needed, one for "nothing to do" and one for "not supported".

-- 
Tilman Schmidt                    E-Mail: tilman@imap.cc
Bonn, Germany
Diese Nachricht besteht zu 100% aus wiederverwerteten Bits.
Ungeöffnet mindestens haltbar bis: (siehe Rückseite)


[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 250 bytes --]

Re: NAK new drivers without proper power management?

[Matthew Garrett]

On Sat, Feb 10, 2007 at 08:57:49AM +1100, Nigel Cunningham wrote:

> Can we start to NAK new drivers that don't have proper power management
> implemented? There really is no excuse for writing a new driver and not
> putting .suspend and .resume methods in anymore, is there?

The PCI layer is able to deal with drivers that have no PM methods in 
the most simple case.

-- 
Matthew Garrett | mjg59@srcf.ucam.org

Re: NAK new drivers without proper power management?

[Nigel Cunningham]

Hi.

On Sat, 2007-02-10 at 03:42 +0000, Matthew Garrett wrote:
> On Sat, Feb 10, 2007 at 08:57:49AM +1100, Nigel Cunningham wrote:
> 
> > Can we start to NAK new drivers that don't have proper power management
> > implemented? There really is no excuse for writing a new driver and not
> > putting .suspend and .resume methods in anymore, is there?
> 
> The PCI layer is able to deal with drivers that have no PM methods in 
> the most simple case.

Yeah. I suppose we could use a pm_safe bit flag in struct device_driver
and/or struct pci_driver. I have other things to do right now, but will
seek to understand the relationship between those structs better later.

Regards,

Nigel

Re: NAK new drivers without proper power management?

[Robert Hancock]

Jeff Garzik wrote:
> Nigel Cunningham wrote:
>> Hi.
>>
>> On Fri, 2007-02-09 at 23:17 +0100, Arjan van de Ven wrote:
>>> On Sat, 2007-02-10 at 08:57 +1100, Nigel Cunningham wrote:
>>>> Hi.
>>>>
>>>> I don't think this is already done (feel free to correct me if I'm
>>>> wrong)..
>>>>
>>>> Can we start to NAK new drivers that don't have proper power management
>>>> implemented? There really is no excuse for writing a new driver and not
>>>> putting .suspend and .resume methods in anymore, is there?
>>>
>>> to a large degree, a device driver that doesn't suspend is better than
>>> no device driver at all, right?
>>
>> I'm not sure it is. It only makes more work for everyone else: We have
>> to help people figure out what causes their computer to fail to resume
>> (which can take quite a while), then get them them complain to driver
>> author, and the driver author has to submit patches to fix it.
>>
>> All of this is avoided if they'll just do it right in the first place.
> 
> A lot of a lot of things could have been avoided, if they just did it 
> right the first time.
> 
> I think it's more valuable to users to get a basic network driver that 
> pings or a basic ATA driver that reads/writes, than peripheral issues 
> like suspend/resume.
> 
> Certainly we should ask for it, but it shouldn't be a merge-stopper.
> 
>     Jeff

I would disagree that it's a peripheral issue, it's pretty core these 
days, at least for any hardware that you can stuff in a laptop (though a 
fair number of desktops get suspended and resumed these days too). One 
driver on a system which doesn't suspend or resume properly can ruin the 
entire process, causing a ton of user frustration. Certainly I would 
consider a driver without suspend/resume support to be incomplete.

The trouble with deferring adding this support is that it's a lot harder 
to add this support in after the fact than if it was considered during 
the original driver development.

I would be in favor of not merging drivers lacking suspend unless 
there's a very good reason they're lacking it.

It also kind of bothers me that if a driver has no suspend/resume 
functions, and you suspend and resume the system, we don't complain 
about it even though there's a very good chance that device is not going 
to function properly. How about something in dmesg like:

Warning: driver for device XXXX has no suspend or resume support.
Device may not function properly after resume.

so that users know who to complain to. Maybe there are some devices that 
truly don't need any handling for suspend, but if so I suspect the 
number of those is small enough that adding empty functions would be a 
good-enough solution.

-- 
Robert Hancock      Saskatoon, SK, Canada
To email, remove "nospam" from hancockr@nospamshaw.ca
Home Page: http://www.roberthancock.com/

Re: NAK new drivers without proper power management?

[Lee Revell]

On 2/9/07, Robert Hancock <hancockr@shaw.ca> wrote:
> I would disagree that it's a peripheral issue, it's pretty core these
> days, at least for any hardware that you can stuff in a laptop (though a
> fair number of desktops get suspended and resumed these days too).

Servers are still the most important Linux market, and don't care
about suspend/resume.  I would consider implementing suspend./resume
for a driver that will only be used in server or HPC class hardware a
waste of valuable development resources.

Lee

Re: NAK new drivers without proper power management?

[Nigel Cunningham]

Hi.

On Fri, 2007-02-09 at 20:59 -0500, Lee Revell wrote:
> On 2/9/07, Robert Hancock <hancockr@shaw.ca> wrote:
> > I would disagree that it's a peripheral issue, it's pretty core these
> > days, at least for any hardware that you can stuff in a laptop (though a
> > fair number of desktops get suspended and resumed these days too).
> 
> Servers are still the most important Linux market, and don't care
> about suspend/resume.  I would consider implementing suspend./resume
> for a driver that will only be used in server or HPC class hardware a
> waste of valuable development resources.

Not necessarily. Imagine suspending to disk in order to replace a faulty
card. That could be way faster and less disruptive than shutting down
normally and loosing caches and so on.

Irrespective of the above, servers tend not to have too much in the way
of hardware unique to them anyway, and even if you don't find it useful,
that's not to say others won't want it.

Regards,

Nigel

Re: NAK new drivers without proper power management?

[Lee Revell]

On 2/9/07, Nigel Cunningham <nigel@nigel.suspend2.net> wrote:
> On Fri, 2007-02-09 at 20:59 -0500, Lee Revell wrote:
> > On 2/9/07, Robert Hancock <hancockr@shaw.ca> wrote:
> > > I would disagree that it's a peripheral issue, it's pretty core these
> > > days, at least for any hardware that you can stuff in a laptop (though a
> > > fair number of desktops get suspended and resumed these days too).
> >
> > Servers are still the most important Linux market, and don't care
> > about suspend/resume.  I would consider implementing suspend./resume
> > for a driver that will only be used in server or HPC class hardware a
> > waste of valuable development resources.
>
> Not necessarily. Imagine suspending to disk in order to replace a faulty
> card. That could be way faster and less disruptive than shutting down
> normally and loosing caches and so on.
>

Hmm.  If uptime is critical I would make sure to have redundant
systems anyway and I would just reboot the thing.  I would not expect
the suspend/resume paths on server class hardware like 10gig ethernet,
Infiniband adapters, or high end SCSI to be particularly well tested.

> Irrespective of the above, servers tend not to have too much in the way
> of hardware unique to them anyway, and even if you don't find it useful,
> that's not to say others won't want it.

Yes but for such hardware, suspend/resume is likely to be a lot of
work to implement, and I'd rather the developers devote those
resources to making the driver as stable and performant as possible.

I agree 100% that drivers for desktop and laptop hardware should be
rejected if missing suspend/resume.

Lee

Re: NAK new drivers without proper power management?

[Kevin Fox]

On Fri, 2007-02-09 at 18:22 -0800, Lee Revell wrote:
> On 2/9/07, Nigel Cunningham <nigel@nigel.suspend2.net> wrote:
> > On Fri, 2007-02-09 at 20:59 -0500, Lee Revell wrote:
> > > On 2/9/07, Robert Hancock <hancockr@shaw.ca> wrote:
> > > > I would disagree that it's a peripheral issue, it's pretty core
> these
> > > > days, at least for any hardware that you can stuff in a laptop
> (though a
> > > > fair number of desktops get suspended and resumed these days
> too).
> > >
> > > Servers are still the most important Linux market, and don't care
> > > about suspend/resume.  I would consider implementing
> suspend./resume
> > > for a driver that will only be used in server or HPC class
> hardware a
> > > waste of valuable development resources.
> >
> > Not necessarily. Imagine suspending to disk in order to replace a
> faulty
> > card. That could be way faster and less disruptive than shutting
> down
> > normally and loosing caches and so on.
> >
> 
> Hmm.  If uptime is critical I would make sure to have redundant
> systems anyway and I would just reboot the thing.  I would not expect
> the suspend/resume paths on server class hardware like 10gig ethernet,
> Infiniband adapters, or high end SCSI to be particularly well tested.

Speaking from the HPC standpoint, we are gaining more and more nodes in
clusters as time goes on, so the potential for single failures affecting
performance is growing. A lot of the server class nodes have redundancy
such that the node slows down but not die on failure. Unfortunately,
slowdown in a single node in a tightly coupled job can greatly affect
performance. A good example would be ECC memory. If a chip is going bad,
the machine can detect it but it will run slower until the memory is
replaced. This one node can affect thousands of other nodes in the same
job. Having a mechanism to migrate the operating system that is running
on this failing node to another node would be quite beneficial to
performance. If all drivers properly supported suspend/resume, it could
possibly be extended to support migration to another node as well. At
least for the HPC world, we'd like to see, and encourage, the hardware
you describe getting full support for suspend/resume.

Kevin

> > Irrespective of the above, servers tend not to have too much in the
> way
> > of hardware unique to them anyway, and even if you don't find it
> useful,
> > that's not to say others won't want it.
> 
> Yes but for such hardware, suspend/resume is likely to be a lot of
> work to implement, and I'd rather the developers devote those
> resources to making the driver as stable and performant as possible.
> 
> I agree 100% that drivers for desktop and laptop hardware should be
> rejected if missing suspend/resume.
> 
> Lee
> -
> To unsubscribe from this list: send the line "unsubscribe
> linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at  http://www.tux.org/lkml/
> 
> 

Re: NAK new drivers without proper power management?

[Adrian Bunk]

On Fri, Feb 09, 2007 at 09:22:48PM -0500, Lee Revell wrote:
> On 2/9/07, Nigel Cunningham <nigel@nigel.suspend2.net> wrote:
> >On Fri, 2007-02-09 at 20:59 -0500, Lee Revell wrote:
> >> On 2/9/07, Robert Hancock <hancockr@shaw.ca> wrote:
> >> > I would disagree that it's a peripheral issue, it's pretty core these
> >> > days, at least for any hardware that you can stuff in a laptop (though 
> >a
> >> > fair number of desktops get suspended and resumed these days too).
> >>
> >> Servers are still the most important Linux market, and don't care
> >> about suspend/resume.  I would consider implementing suspend./resume
> >> for a driver that will only be used in server or HPC class hardware a
> >> waste of valuable development resources.
> >
> >Not necessarily. Imagine suspending to disk in order to replace a faulty
> >card. That could be way faster and less disruptive than shutting down
> >normally and loosing caches and so on.
> >
> 
> Hmm.  If uptime is critical I would make sure to have redundant
> systems anyway and I would just reboot the thing.  I would not expect
> the suspend/resume paths on server class hardware like 10gig ethernet,
> Infiniband adapters, or high end SCSI to be particularly well tested.
>...

10gig ethernet will be commodity hardware 5 years from now like 
1gig ethernet today where you can get cards for 12 Euro and switches for 
40 Euro.

> Lee

cu
Adrian

-- 

       "Is there not promise of rain?" Ling Tan asked suddenly out
        of the darkness. There had been need of rain for many days.
       "Only a promise," Lao Er said.
                                       Pearl S. Buck - Dragon Seed

Re: NAK new drivers without proper power management?

[Joseph Fannin]

On Fri, Feb 09, 2007 at 08:59:55PM -0500, Lee Revell wrote:
> On 2/9/07, Robert Hancock <hancockr@shaw.ca> wrote:
> >I would disagree that it's a peripheral issue, it's pretty core these
> >days, at least for any hardware that you can stuff in a laptop (though a
> >fair number of desktops get suspended and resumed these days too).
>
> Servers are still the most important Linux market, and don't care
> about suspend/resume.  I would consider implementing suspend./resume
> for a driver that will only be used in server or HPC class hardware a
> waste of valuable development resources.

    Please allow me to be offensively blunt for a moment.

    So, the situation seems to be:

    1. The work of the suspend developer who engages the users who put
       effort into making suspend work on their hardware (bless
       their addled little heads) often doesn't meet kernel standards,
       or isn't well enough documented to prove the real *need* for
       the features and/or hacks that have happened to get actual
       users' systems sleeping and running again.

    2. The swsusp maintainer continues in the belief that as long as
       their are no bug reports in kernel bugzilla or crossing the
       (relatively obscure) swsusp mailing lists, it has zarro boogs
       and meanwhile works on the fourth implementation of suspend
       support in as many years.  It's in CVS on sourceforge.  There's
       no documentation whatsoever.

    3. There's another guy who appears to be doing a lot of work, so I
       shan't leave him out.  Like the two developers previously
       mentioned, he seems to be working pretty hard on the whole
       thing.  The previously mentioned fourth suspend implementation
       seems to be largely his doing, for good and for ill.

    4. "Everybody" knows suspend doesn't work on Linux without a huge
       amount of tinkering, deep magic, and dead chickens.  Only
       Gentoo users seem to bother; everyone else waits for Ubuntu
       12.04 wherein suspend will "just work".  The Gentoo users all
       use swsusp2, as it contains the hacks to work around:

    5. All the suspend developers blame the lack of power-management
       support in drivers for the inablility of Linux to properly
       suspend on anything that doesn't support APM.

    6. Getting proper power-management support in Linux device drivers
       is not a priority; drivers without any power management support
       whatsoever should not only be accepted -- they should be merged
       without comment or complaint.

   How is working suspend support ever supposed to happen?

--
Joseph Fannin
jfannin@gmail.com || jhf@columbus.rr.com

Re: NAK new drivers without proper power management?

[Pavel Machek]

Hi!

> > >I would disagree that it's a peripheral issue, it's pretty core these
> > >days, at least for any hardware that you can stuff in a laptop (though a
> > >fair number of desktops get suspended and resumed these days too).
> >
> > Servers are still the most important Linux market, and don't care
> > about suspend/resume.  I would consider implementing suspend./resume
> > for a driver that will only be used in server or HPC class hardware a
> > waste of valuable development resources.
> 
>     Please allow me to be offensively blunt for a moment.
> 
>     So, the situation seems to be:
> 
>     1. The work of the suspend developer who engages the users who put
>        effort into making suspend work on their hardware (bless
>        their addled little heads) often doesn't meet kernel standards,
>        or isn't well enough documented to prove the real *need* for
>        the features and/or hacks that have happened to get actual
>        users' systems sleeping and running again.
> 
>     2. The swsusp maintainer continues in the belief that as long as
>        their are no bug reports in kernel bugzilla or crossing the
>        (relatively obscure) swsusp mailing lists, it has zarro boogs
>        and meanwhile works on the fourth implementation of suspend
>        support in as many years.  It's in CVS on sourceforge.  There's
>        no documentation whatsoever.
....
>     4. "Everybody" knows suspend doesn't work on Linux without a huge
>        amount of tinkering, deep magic, and dead chickens.  Only
>        Gentoo users seem to bother; everyone else waits for Ubuntu
>        12.04 wherein suspend will "just work".  The Gentoo users all
>        use swsusp2, as it contains the hacks to work around:

Suspend just works in suse10.2 (and suse10.1, and suse10.0, ...)...
thanks to work seife did on pm scripts. It
is not my fault if it is broken on your distro.

>     6. Getting proper power-management support in Linux device drivers
>        is not a priority; drivers without any power management support
>        whatsoever should not only be accepted -- they should be merged
>        without comment or complaint.
> 
>    How is working suspend support ever supposed to happen?

If people stopped sending rants and started sending patches... yep,
that would help. I don't have all the notebooks ever produced, sorry.

							Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

Re: NAK new drivers without proper power management?

[Stefan Richter]

Lee Revell wrote:
> Servers are still the most important Linux market,

To whom?
-- 
Stefan Richter
-=====-=-=== --=- -=-=-
http://arcgraph.de/sr/

Re: NAK new drivers without proper power management?

[Nigel Cunningham]

Hi.

On Fri, 2007-02-09 at 19:50 -0600, Robert Hancock wrote:
> Jeff Garzik wrote:
> > Nigel Cunningham wrote:
> >> Hi.
> >>
> >> On Fri, 2007-02-09 at 23:17 +0100, Arjan van de Ven wrote:
> >>> On Sat, 2007-02-10 at 08:57 +1100, Nigel Cunningham wrote:
> >>>> Hi.
> >>>>
> >>>> I don't think this is already done (feel free to correct me if I'm
> >>>> wrong)..
> >>>>
> >>>> Can we start to NAK new drivers that don't have proper power management
> >>>> implemented? There really is no excuse for writing a new driver and not
> >>>> putting .suspend and .resume methods in anymore, is there?
> >>>
> >>> to a large degree, a device driver that doesn't suspend is better than
> >>> no device driver at all, right?
> >>
> >> I'm not sure it is. It only makes more work for everyone else: We have
> >> to help people figure out what causes their computer to fail to resume
> >> (which can take quite a while), then get them them complain to driver
> >> author, and the driver author has to submit patches to fix it.
> >>
> >> All of this is avoided if they'll just do it right in the first place.
> > 
> > A lot of a lot of things could have been avoided, if they just did it 
> > right the first time.
> > 
> > I think it's more valuable to users to get a basic network driver that 
> > pings or a basic ATA driver that reads/writes, than peripheral issues 
> > like suspend/resume.
> > 
> > Certainly we should ask for it, but it shouldn't be a merge-stopper.
> > 
> >     Jeff
> 
> I would disagree that it's a peripheral issue, it's pretty core these 
> days, at least for any hardware that you can stuff in a laptop (though a 
> fair number of desktops get suspended and resumed these days too). One 
> driver on a system which doesn't suspend or resume properly can ruin the 
> entire process, causing a ton of user frustration. Certainly I would 
> consider a driver without suspend/resume support to be incomplete.
> 
> The trouble with deferring adding this support is that it's a lot harder 
> to add this support in after the fact than if it was considered during 
> the original driver development.
> 
> I would be in favor of not merging drivers lacking suspend unless 
> there's a very good reason they're lacking it.
> 
> It also kind of bothers me that if a driver has no suspend/resume 
> functions, and you suspend and resume the system, we don't complain 
> about it even though there's a very good chance that device is not going 
> to function properly. How about something in dmesg like:
> 
> Warning: driver for device XXXX has no suspend or resume support.
> Device may not function properly after resume.
> 
> so that users know who to complain to. Maybe there are some devices that 
> truly don't need any handling for suspend, but if so I suspect the 
> number of those is small enough that adding empty functions would be a 
> good-enough solution.

I've already made a start on doing just that. Rafael was clearly right
in asserting that some drivers would need to have warnings suppressed,
but that can be dealt with (see below).

Even if no-one wants it for vanilla, I think I'll put this in Suspend2.
It will at least help my users with debugging issues.

Regards,

Nigel

[   14.936667] Device driver platform lacks bus and class support for being suspended or resumed.
[   14.937612] Device driver vtcon0 lacks bus and class support for being suspended or resumed.
[   14.955258] Device driver pci0000:00 lacks bus and class support for being suspended or resumed.
[   15.004268] Device driver pnp0 lacks bus and class support for being suspended or resumed.
[   15.010618] Device driver mem lacks bus and class support for being suspended or resumed.
[   15.010779] Device driver kmem lacks bus and class support for being suspended or resumed.
[   15.010932] Device driver null lacks bus and class support for being suspended or resumed.
[   15.011090] Device driver port lacks bus and class support for being suspended or resumed.
[   15.011248] Device driver zero lacks bus and class support for being suspended or resumed.
[   15.011414] Device driver full lacks bus and class support for being suspended or resumed.
[   15.011566] Device driver random lacks bus and class support for being suspended or resumed.
[   15.011723] Device driver urandom lacks bus and class support for being suspended or resumed.
[   15.011875] Device driver kmsg lacks bus and class support for being suspended or resumed.
[   15.305495] Device driver mcelog lacks bus and class support for being suspended or resumed.
[   15.305688] Device driver msr0 lacks bus and class support for being suspended or resumed.
[   15.306571] Device driver snapshot lacks bus and class support for being suspended or resumed.
[   15.359006] Device driver fb0 lacks bus and class support for being suspended or resumed.
[   15.359471] Device driver vtcon1 lacks bus and class support for being suspended or resumed.
[   15.455642] Device driver tty lacks bus and class support for being suspended or resumed.
[   15.455815] Device driver console lacks bus and class support for being suspended or resumed.
[   15.455991] Device driver ptmx lacks bus and class support for being suspended or resumed.
[   15.456157] Device driver tty0 lacks bus and class support for being suspended or resumed.
[   15.456336] Device driver vcs lacks bus and class support for being suspended or resumed.
[   15.456495] Device driver vcsa lacks bus and class support for being suspended or resumed.
[   15.456668] Device driver tty1 lacks bus and class support for being suspended or resumed.
[   15.456860] Device driver tty2 lacks bus and class support for being suspended or resumed.
[   15.457057] Device driver tty3 lacks bus and class support for being suspended or resumed.
[   15.457256] Device driver tty4 lacks bus and class support for being suspended or resumed.
[   15.457447] Device driver tty5 lacks bus and class support for being suspended or resumed.
[   15.457642] Device driver tty6 lacks bus and class support for being suspended or resumed.
[   15.457833] Device driver tty7 lacks bus and class support for being suspended or resumed.
[   15.458024] Device driver tty8 lacks bus and class support for being suspended or resumed.
[   15.458219] Device driver tty9 lacks bus and class support for being suspended or resumed.
[   15.458419] Device driver tty10 lacks bus and class support for being suspended or resumed.
[   15.458615] Device driver tty11 lacks bus and class support for being suspended or resumed.
[   15.458808] Device driver tty12 lacks bus and class support for being suspended or resumed.
...
[   15.469106] Device driver rtc lacks bus and class support for being suspended or resumed.
[   15.469283] Device driver hpet lacks bus and class support for being suspended or resumed.
[   15.469585] Device driver ttyS0 lacks bus and class support for being suspended or resumed.
[   15.469777] Device driver ttyS1 lacks bus and class support for being suspended or resumed.
[   15.469972] Device driver ttyS2 lacks bus and class support for being suspended or resumed.
[   15.470173] Device driver ttyS3 lacks bus and class support for being suspended or resumed.
[   15.470808] Device driver ttyS0 lacks bus and class support for being suspended or resumed.
[   15.471159] Device driver ttyS0 lacks bus and class support for being suspended or resumed.
[   15.471501] Device driver ttyS0 lacks bus and class support for being suspended or resumed.
[   15.471844] Device driver ttyS0 lacks bus and class support for being suspended or resumed.
[   15.472213] Device driver ttyS0 lacks bus and class support for being suspended or resumed.
[   15.472583] Device driver ttyS1 lacks bus and class support for being suspended or resumed.
[   15.472916] Device driver ttyS2 lacks bus and class support for being suspended or resumed.
[   15.473271] Device driver ttyS2 lacks bus and class support for being suspended or resumed.
[   15.473641] Device driver ttyS2 lacks bus and class support for being suspended or resumed.
[   15.474009] Device driver ttyS3 lacks bus and class support for being suspended or resumed.
[   15.775682] Device driver ide0 lacks bus and class support for being suspended or resumed.
[   17.632766] Device driver ide1 lacks bus and class support for being suspended or resumed.
[   17.633462] PCI driver ALI15x3_IDE lacks driver specific suspend and resume support.
[   17.633465] PCI driver ALI15x3_IDE lacks a driver specific resume method.
[   17.633547] PCI driver PIIX_IDE lacks driver specific suspend and resume support.
[   17.633549] PCI driver PIIX_IDE lacks a driver specific resume method.
[   17.684475] Device driver serio0 lacks bus and class support for being resumed.
[   17.684724] Device driver serio1 lacks bus and class support for being resumed.
[   17.684874] Device driver psaux lacks bus and class support for being suspended or resumed.
[   17.685015] Device driver serio2 lacks bus and class support for being resumed.
[   18.373576] Device driver serio3 lacks bus and class support for being resumed.
[   18.375666] Device driver serio4 lacks bus and class support for being resumed.
...
[   22.656888] Device driver timer lacks bus and class support for being suspended or resumed.
[   23.314970] Device driver pcmC0D2p lacks bus and class support for being suspended or resumed.
[   23.315327] Device driver pcmC0D1c lacks bus and class support for being suspended or resumed.
[   23.315648] Device driver adsp lacks bus and class support for being suspended or resumed.
[   23.316036] Device driver pcmC0D0p lacks bus and class support for being suspended or resumed.
[   23.316352] Device driver pcmC0D0c lacks bus and class support for being suspended or resumed.
[   23.316672] Device driver dsp lacks bus and class support for being suspended or resumed.
[   23.317053] Device driver audio lacks bus and class support for being suspended or resumed.
[   23.317530] Device driver controlC0 lacks bus and class support for being suspended or resumed.
[   23.317875] Device driver mixer lacks bus and class support for being suspended or resumed.
[   28.806277] Device driver vcs1 lacks bus and class support for being suspended or resumed.
[   28.806479] Device driver vcsa1 lacks bus and class support for being suspended or resumed.
[   71.656860] Device driver vcs1 lacks bus and class support for being suspended or resumed.
[   71.657062] Device driver vcsa1 lacks bus and class support for being suspended or resumed.
[   71.657563] Device driver vcs1 lacks bus and class support for being suspended or resumed.
[   71.657758] Device driver vcsa1 lacks bus and class support for being suspended or resumed.
[   71.658342] Device driver vcs1 lacks bus and class support for being suspended or resumed.
[   71.658530] Device driver vcsa1 lacks bus and class support for being suspended or resumed.
[   71.674825] Device driver vcs1 lacks bus and class support for being suspended or resumed.
[   71.675010] Device driver vcsa1 lacks bus and class support for being suspended or resumed.
[   75.573394] PCI driver ali15x3_smbus lacks driver specific suspend and resume support.
[   75.573396] PCI driver ali15x3_smbus lacks a driver specific resume method.
[   75.844125] Device driver usbdev1.1_ep00 lacks bus and class support for being suspended or resumed.
[   75.951810] Device driver usbdev1.1_ep81 lacks bus and class support for being suspended or resumed.
[   76.013809] Device driver usbdev2.1_ep00 lacks bus and class support for being suspended or resumed.
[   76.121522] Device driver usbdev2.1_ep81 lacks bus and class support for being suspended or resumed.
[   76.122026] PCI driver ali1535_smbus lacks driver specific suspend and resume support.
[   76.122028] PCI driver ali1535_smbus lacks a driver specific resume method.
[   76.151696] Device driver usbdev3.1_ep00 lacks bus and class support for being suspended or resumed.
[   76.301270] Device driver usbdev3.1_ep81 lacks bus and class support for being suspended or resumed.
[   86.348191] Device driver vcs7 lacks bus and class support for being suspended or resumed.
[   86.348373] Device driver vcsa7 lacks bus and class support for being suspended or resumed.
[  113.547039] Device driver vmmon lacks bus and class support for being suspended or resumed.

Re: NAK new drivers without proper power management?

[Dmitry Torokhov]

Hi Nigel,

On Friday 09 February 2007 21:05, Nigel Cunningham wrote:
> [   17.684475] Device driver serio0 lacks bus and class support for being resumed.
> [   17.684724] Device driver serio1 lacks bus and class support for being resumed.
> [   17.684874] Device driver psaux lacks bus and class support for being suspended or resumed.
> [   17.685015] Device driver serio2 lacks bus and class support for being resumed.
> [   18.373576] Device driver serio3 lacks bus and class support for being resumed.
> [   18.375666] Device driver serio4 lacks bus and class support for being resumed.
> 

You should probably only warn if driver does not have resume method - not
having suspend is quite valid if driver is able to restore state at resume
without explicitely saving anything at suspend time.

-- 
Dmitry

Re: NAK new drivers without proper power management?

[Nigel Cunningham]

Hi Dmitry!

On Fri, 2007-02-09 at 22:27 -0500, Dmitry Torokhov wrote:
> Hi Nigel,
> 
> On Friday 09 February 2007 21:05, Nigel Cunningham wrote:
> > [   17.684475] Device driver serio0 lacks bus and class support for being resumed.
> > [   17.684724] Device driver serio1 lacks bus and class support for being resumed.
> > [   17.684874] Device driver psaux lacks bus and class support for being suspended or resumed.
> > [   17.685015] Device driver serio2 lacks bus and class support for being resumed.
> > [   18.373576] Device driver serio3 lacks bus and class support for being resumed.
> > [   18.375666] Device driver serio4 lacks bus and class support for being resumed.
> > 
> 
> You should probably only warn if driver does not have resume method - not
> having suspend is quite valid if driver is able to restore state at resume
> without explicitely saving anything at suspend time.

Can do. Will do :)

Nigel

Re: NAK new drivers without proper power management?

[Robert Hancock]

Nigel Cunningham wrote:
> If your device requires power management, and you know it requires power
> management, why not just implement power management? Doing -ENOSYS
> instead is like saying -ESPAMMEBECAUSEIMLAZY.
> 
> Let me put it another way: People keep talking about Linux being ready
> for the desktop. To me at least (but I dare say for lots of other people
> too), being ready for the desktop means that things just work, without
> having to recompile kernels or bug driver authors or wait twelve
> months. 
> 
> And it means that doing a bare minimum isn't enough. We keep claiming
> that Open Source is better than Proprietary software. If we accept
> half-pie jobs of implementing support for anything - driver power
> management support or hibernation support or whatever - as 'good
> enough', we're undercutting that argument. Linux's power management
> support should - as far as we're able - be at least as good as that
> other operating system's and preferably way, way better.
> 
> -ENOSYS is just not acceptable.

Well, it's probably more acceptable than silently doing nothing and the 
device failing or locking up the machine on resume, but I couldn't agree 
more that it's not what we want to be encouraging. Perfect may be the 
enemy of the good, but "works except no power management" is hardly what 
I would call good these days, more like pretty sloppy..

-- 
Robert Hancock      Saskatoon, SK, Canada
To email, remove "nospam" from hancockr@nospamshaw.ca
Home Page: http://www.roberthancock.com/

Re: NAK new drivers without proper power management?

[Rafael J. Wysocki]

On Sunday, 11 February 2007 00:20, Robert Hancock wrote:
> Nigel Cunningham wrote:
> > If your device requires power management, and you know it requires power
> > management, why not just implement power management? Doing -ENOSYS
> > instead is like saying -ESPAMMEBECAUSEIMLAZY.
> > 
> > Let me put it another way: People keep talking about Linux being ready
> > for the desktop. To me at least (but I dare say for lots of other people
> > too), being ready for the desktop means that things just work, without
> > having to recompile kernels or bug driver authors or wait twelve
> > months. 
> > 
> > And it means that doing a bare minimum isn't enough. We keep claiming
> > that Open Source is better than Proprietary software. If we accept
> > half-pie jobs of implementing support for anything - driver power
> > management support or hibernation support or whatever - as 'good
> > enough', we're undercutting that argument. Linux's power management
> > support should - as far as we're able - be at least as good as that
> > other operating system's and preferably way, way better.
> > 
> > -ENOSYS is just not acceptable.
> 
> Well, it's probably more acceptable than silently doing nothing and the 
> device failing or locking up the machine on resume, but I couldn't agree 
> more that it's not what we want to be encouraging. Perfect may be the 
> enemy of the good, but "works except no power management" is hardly what 
> I would call good these days, more like pretty sloppy..

I think there are situations in which it can be justified, like:
- The driver is not entirely finished, but we want to merge it early, because
of many potential users,
- The driver has only a few users who aren't interested in the suspend/resume
functionality,
- The device is undocumented and we don't know how to make it handle the
suspend/resume (we may learn that in the future or not).

For this reason I 100% agree that we should _encourage_ implementing .suspend
and .resume, but we should not make it an unbreakable rule cast in stone.

Greetings,
Rafael


-- 
If you don't have the time to read,
you don't have the time or the tools to write.
		- Stephen King

Re: NAK new drivers without proper power management?

[Pavel Machek]

Hi!

> > > -ENOSYS is just not acceptable.
> > 
> > Well, it's probably more acceptable than silently doing nothing and the 
> > device failing or locking up the machine on resume, but I couldn't agree 
> > more that it's not what we want to be encouraging. Perfect may be the 
> > enemy of the good, but "works except no power management" is hardly what 
> > I would call good these days, more like pretty sloppy..
> 
> I think there are situations in which it can be justified, like:
> - The driver is not entirely finished, but we want to merge it early, because
> of many potential users,
> - The driver has only a few users who aren't interested in the suspend/resume
> functionality,
> - The device is undocumented and we don't know how to make it handle the
> suspend/resume (we may learn that in the future or not).
> 
> For this reason I 100% agree that we should _encourage_ implementing .suspend
> and .resume, but we should not make it an unbreakable rule cast in stone.

No rules are ever unbreakable, so that should be okay. 'Make it
suspend, if you can't for some good reason, at least return -ENOSYS
from .suspend' sounds good to me.
							Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

Re: NAK new drivers without proper power management?

[Nigel Cunningham]

Hi.

On Sun, 2007-02-11 at 01:44 +0100, Rafael J. Wysocki wrote:
> > Well, it's probably more acceptable than silently doing nothing and the 
> > device failing or locking up the machine on resume, but I couldn't agree 
> > more that it's not what we want to be encouraging. Perfect may be the 
> > enemy of the good, but "works except no power management" is hardly what 
> > I would call good these days, more like pretty sloppy..
> 
> I think there are situations in which it can be justified, like:
> - The driver is not entirely finished, but we want to merge it early, because
> of many potential users,
> - The driver has only a few users who aren't interested in the suspend/resume
> functionality,

How do you determine that? How many users have to want suspend/resume
functionality before you say "Ok. It has to be done now"?

> - The device is undocumented and we don't know how to make it handle the
> suspend/resume (we may learn that in the future or not).

If we know how to initialise/cleanup, we know a good portion of what is
needed for suspend/resume. Sure, for some video chipsets, you need more
(you need to know how to reprogram the whole thing after S3), but
they're the exception. Yes, there are other cases. But on the whole,
we're not talking about esoteric knowledge.

Regards,

Nigel

Re: NAK new drivers without proper power management?

[Rafael J. Wysocki]

On Sunday, 11 February 2007 23:40, Nigel Cunningham wrote:
> Hi.
> 
> On Sun, 2007-02-11 at 01:44 +0100, Rafael J. Wysocki wrote:
> > > Well, it's probably more acceptable than silently doing nothing and the 
> > > device failing or locking up the machine on resume, but I couldn't agree 
> > > more that it's not what we want to be encouraging. Perfect may be the 
> > > enemy of the good, but "works except no power management" is hardly what 
> > > I would call good these days, more like pretty sloppy..
> > 
> > I think there are situations in which it can be justified, like:
> > - The driver is not entirely finished, but we want to merge it early, because
> > of many potential users,
> > - The driver has only a few users who aren't interested in the suspend/resume
> > functionality,
> 
> How do you determine that? How many users have to want suspend/resume
> functionality before you say "Ok. It has to be done now"?

That depends on what the driver author tells us.  If he says there's only one
such device in the world and it needs a Linux drivers, but the system in
question will never be suspended, that will be fine, I think.  There are such
cases already and I see no reason why there won't be any more in the future.

> > - The device is undocumented and we don't know how to make it handle the
> > suspend/resume (we may learn that in the future or not).
> 
> If we know how to initialise/cleanup, we know a good portion of what is
> needed for suspend/resume. Sure, for some video chipsets, you need more
> (you need to know how to reprogram the whole thing after S3), but
> they're the exception. Yes, there are other cases. But on the whole,
> we're not talking about esoteric knowledge.

No, in general this is not _that_ simple.  Please browse the archives of
bcm43xx-dev, for example.

While I agree that the support for suspend and resume _is_ generally important,
I also admit that there are situations in which it doesn't matter and there are
many people who won't care a whit for it.

Greetings,
Rafael 

Re: NAK new drivers without proper power management?

[Nigel Cunningham]

Hi.

On Mon, 2007-02-12 at 00:29 +0100, Rafael J. Wysocki wrote:
> > On Sun, 2007-02-11 at 01:44 +0100, Rafael J. Wysocki wrote:
> > > > Well, it's probably more acceptable than silently doing nothing and the 
> > > > device failing or locking up the machine on resume, but I couldn't agree 
> > > > more that it's not what we want to be encouraging. Perfect may be the 
> > > > enemy of the good, but "works except no power management" is hardly what 
> > > > I would call good these days, more like pretty sloppy..
> > > 
> > > I think there are situations in which it can be justified, like:
> > > - The driver is not entirely finished, but we want to merge it early, because
> > > of many potential users,
> > > - The driver has only a few users who aren't interested in the suspend/resume
> > > functionality,
> > 
> > How do you determine that? How many users have to want suspend/resume
> > functionality before you say "Ok. It has to be done now"?
> 
> That depends on what the driver author tells us.  If he says there's only one
> such device in the world and it needs a Linux drivers, but the system in
> question will never be suspended, that will be fine, I think.  There are such
> cases already and I see no reason why there won't be any more in the future.
> 
> > > - The device is undocumented and we don't know how to make it handle the
> > > suspend/resume (we may learn that in the future or not).
> > 
> > If we know how to initialise/cleanup, we know a good portion of what is
> > needed for suspend/resume. Sure, for some video chipsets, you need more
> > (you need to know how to reprogram the whole thing after S3), but
> > they're the exception. Yes, there are other cases. But on the whole,
> > we're not talking about esoteric knowledge.
> 
> No, in general this is not _that_ simple.  Please browse the archives of
> bcm43xx-dev, for example.

Yeah. The problems of not having documentation + having to reassociate
and so on.

> While I agree that the support for suspend and resume _is_ generally important,
> I also admit that there are situations in which it doesn't matter and there are
> many people who won't care a whit for it.

Ok, but that's the exception, right? Not the rule? So in those cases, an
exception is made.

Regards,

Nigel

Re: NAK new drivers without proper power management?

[Robert Hancock]

Willy Tarreau wrote:
> Nigel, don't take it as a personal offense, but I think it is a very
> centric view of Linux usages. Where I work, Linux is used a lot on
> servers and appliances. It is used for mail relays, HTTP proxies,
> anti-viruses, firewalls, routers, load balancers, UTM, SSH relays,
> etc... Nobody would ever want to enable power management on those
> machines, let alone suspend which would cause a major havoc, would
> the system decide to enter suspend for any reason.
> 
> Many people also have Linux on their notebooks, but as a dual-boot. You
> read the word ? "dual-boot". It means that they cleanly shutdown their
> system every time they don't use it anymore, and they won't know what
> OS they'll use next time.
> 
> I've never heard anyone there complaining "oh, I'm fed up with this
> boring boot, I always have to wait 30 seconds when I need to do
> something, I wish I could suspend and resume". It is considered the
> normal way of using their PCs.

I think your experience is rather different than that of Joe Average 
User who doesn't frequent kernel lists, and also I think you'll find 
that for a lot of Linux laptop users that don't use supend, the reason 
is that it doesn't work reliably, quite often due to driver issues.

-- 
Robert Hancock      Saskatoon, SK, Canada
To email, remove "nospam" from hancockr@nospamshaw.ca
Home Page: http://www.roberthancock.com/

Re: NAK new drivers without proper power management?

[Willy Tarreau]

On Sun, Feb 11, 2007 at 12:31:14PM -0600, Robert Hancock wrote:
> Willy Tarreau wrote:
> >Nigel, don't take it as a personal offense, but I think it is a very
> >centric view of Linux usages. Where I work, Linux is used a lot on
> >servers and appliances. It is used for mail relays, HTTP proxies,
> >anti-viruses, firewalls, routers, load balancers, UTM, SSH relays,
> >etc... Nobody would ever want to enable power management on those
> >machines, let alone suspend which would cause a major havoc, would
> >the system decide to enter suspend for any reason.
> >
> >Many people also have Linux on their notebooks, but as a dual-boot. You
> >read the word ? "dual-boot". It means that they cleanly shutdown their
> >system every time they don't use it anymore, and they won't know what
> >OS they'll use next time.
> >
> >I've never heard anyone there complaining "oh, I'm fed up with this
> >boring boot, I always have to wait 30 seconds when I need to do
> >something, I wish I could suspend and resume". It is considered the
> >normal way of using their PCs.
> 
> I think your experience is rather different than that of Joe Average 
> User who doesn't frequent kernel lists, and also I think you'll find 
> that for a lot of Linux laptop users that don't use supend, the reason 
> is that it doesn't work reliably, quite often due to driver issues.

I would believe it if I knew people using suspend/resume on the other OS.
But that's not the case either. Also, it happens that with today's RAM
sizes, suspend-to-disk then resume can be several times slower than a
clean fresh boot. When you have 1 GB to write at 20 MB/s, it takes 50
seconds to shut down, and as much to restart. Compare this to 5-10
seconds for a shutdown and 30-50 seconds for a cold boot, and it might
give you another clue why there are people not interested in such a
feature.

Regards,
Willy

Re: NAK new drivers without proper power management?

[Nigel Cunningham]

Hi.

On Sun, 2007-02-11 at 22:52 +0100, Willy Tarreau wrote:
> On Sun, Feb 11, 2007 at 12:31:14PM -0600, Robert Hancock wrote:
> > Willy Tarreau wrote:
> > >Nigel, don't take it as a personal offense, but I think it is a very
> > >centric view of Linux usages. Where I work, Linux is used a lot on
> > >servers and appliances. It is used for mail relays, HTTP proxies,
> > >anti-viruses, firewalls, routers, load balancers, UTM, SSH relays,
> > >etc... Nobody would ever want to enable power management on those
> > >machines, let alone suspend which would cause a major havoc, would
> > >the system decide to enter suspend for any reason.
> > >
> > >Many people also have Linux on their notebooks, but as a dual-boot. You
> > >read the word ? "dual-boot". It means that they cleanly shutdown their
> > >system every time they don't use it anymore, and they won't know what
> > >OS they'll use next time.
> > >
> > >I've never heard anyone there complaining "oh, I'm fed up with this
> > >boring boot, I always have to wait 30 seconds when I need to do
> > >something, I wish I could suspend and resume". It is considered the
> > >normal way of using their PCs.
> > 
> > I think your experience is rather different than that of Joe Average 
> > User who doesn't frequent kernel lists, and also I think you'll find 
> > that for a lot of Linux laptop users that don't use supend, the reason 
> > is that it doesn't work reliably, quite often due to driver issues.
> 
> I would believe it if I knew people using suspend/resume on the other OS.
> But that's not the case either. Also, it happens that with today's RAM
> sizes, suspend-to-disk then resume can be several times slower than a
> clean fresh boot. When you have 1 GB to write at 20 MB/s, it takes 50
> seconds to shut down, and as much to restart. Compare this to 5-10
> seconds for a shutdown and 30-50 seconds for a cold boot, and it might
> give you another clue why there are people not interested in such a
> feature.

I'm using M$ hibernation and Suspend2 to dual boot on our desktop (dtv
card that Linux doesn't support well yet), and I know other Suspend2
users doing the same. It's made earier by the fact that Suspend2 lets
you reboot instead of powering down.

As to comparing the speed with the time to boot, your estimates are way
out. Both will of course vary with the harddrive and cpu speeds and
compression qualities of the image, but with Suspend2, I'm seeing speeds
more in the range of 40-100MB/s, and even had a resport of 160MB/s a
couple of days ago. The rule of thumb I use is:

Run hdparm -t (or equiv) on the drive you'll be using:

nigel@nigel:~$ sudo hdparm -t /dev/hda

/dev/hda:
 Timing buffered disk reads:  120 MB in  3.02 seconds =  39.70 MB/sec

Then calculate RAM_IN_MB / 2 / HDPARM_RESULT = seconds to read/write
image.

In my case: 1024 / 2 / 39.7 = approx 12 seconds. The / 2 is because with
LZF compression, you normally get about 50% compression.

I think the mean reason some people aren't interested in suspend to disk
is because of myths (if you'll excuse the term) like the one you've put
above. Of course that values you give were more accurate for swsusp and
uswsusp until recently, but Suspend2 has had async I/O and compression
for years, so all I can really do is encourage you to try again.

Of course there's another factor you're not taking into account: With
suspending to disk, you don't have to close and reopen documents or shut
down and restart applications. The time to do that should be factored
into the non-suspend-to-disk time to compare apples with apples.

Regards,

Nigel

Re: NAK new drivers without proper power management?

[Willy Tarreau]

On Mon, Feb 12, 2007 at 09:26:26AM +1100, Nigel Cunningham wrote:
> Hi.
> 
> On Sun, 2007-02-11 at 22:52 +0100, Willy Tarreau wrote:
> > On Sun, Feb 11, 2007 at 12:31:14PM -0600, Robert Hancock wrote:
> > > Willy Tarreau wrote:
> > > >Nigel, don't take it as a personal offense, but I think it is a very
> > > >centric view of Linux usages. Where I work, Linux is used a lot on
> > > >servers and appliances. It is used for mail relays, HTTP proxies,
> > > >anti-viruses, firewalls, routers, load balancers, UTM, SSH relays,
> > > >etc... Nobody would ever want to enable power management on those
> > > >machines, let alone suspend which would cause a major havoc, would
> > > >the system decide to enter suspend for any reason.
> > > >
> > > >Many people also have Linux on their notebooks, but as a dual-boot. You
> > > >read the word ? "dual-boot". It means that they cleanly shutdown their
> > > >system every time they don't use it anymore, and they won't know what
> > > >OS they'll use next time.
> > > >
> > > >I've never heard anyone there complaining "oh, I'm fed up with this
> > > >boring boot, I always have to wait 30 seconds when I need to do
> > > >something, I wish I could suspend and resume". It is considered the
> > > >normal way of using their PCs.
> > > 
> > > I think your experience is rather different than that of Joe Average 
> > > User who doesn't frequent kernel lists, and also I think you'll find 
> > > that for a lot of Linux laptop users that don't use supend, the reason 
> > > is that it doesn't work reliably, quite often due to driver issues.
> > 
> > I would believe it if I knew people using suspend/resume on the other OS.
> > But that's not the case either. Also, it happens that with today's RAM
> > sizes, suspend-to-disk then resume can be several times slower than a
> > clean fresh boot. When you have 1 GB to write at 20 MB/s, it takes 50
> > seconds to shut down, and as much to restart. Compare this to 5-10
> > seconds for a shutdown and 30-50 seconds for a cold boot, and it might
> > give you another clue why there are people not interested in such a
> > feature.
> 
> I'm using M$ hibernation and Suspend2 to dual boot on our desktop (dtv
> card that Linux doesn't support well yet), and I know other Suspend2
> users doing the same. It's made earier by the fact that Suspend2 lets
> you reboot instead of powering down.
> 
> As to comparing the speed with the time to boot, your estimates are way
> out. Both will of course vary with the harddrive and cpu speeds and
> compression qualities of the image, but with Suspend2, I'm seeing speeds
> more in the range of 40-100MB/s, and even had a resport of 160MB/s a
> couple of days ago. The rule of thumb I use is:
> 
> Run hdparm -t (or equiv) on the drive you'll be using:
> 
> nigel@nigel:~$ sudo hdparm -t /dev/hda
> 
> /dev/hda:
>  Timing buffered disk reads:  120 MB in  3.02 seconds =  39.70 MB/sec
> 
> Then calculate RAM_IN_MB / 2 / HDPARM_RESULT = seconds to read/write
> image.
> 
> In my case: 1024 / 2 / 39.7 = approx 12 seconds. The / 2 is because with
> LZF compression, you normally get about 50% compression.
> 
> I think the mean reason some people aren't interested in suspend to disk
> is because of myths (if you'll excuse the term) like the one you've put
> above. Of course that values you give were more accurate for swsusp and
> uswsusp until recently, but Suspend2 has had async I/O and compression
> for years, so all I can really do is encourage you to try again.

Well, I agree that you give some good arguments here.

> Of course there's another factor you're not taking into account: With
> suspending to disk, you don't have to close and reopen documents or shut
> down and restart applications. The time to do that should be factored
> into the non-suspend-to-disk time to compare apples with apples.

Hmm sorry, but we don't have the same usages of notebooks. For no reason
would I keep documents open, for two reasons :

  - when I shutdown my notebook, it is to move from one customer to
    home/company/another customer. There's no related work anyway, the
    network will have changed and I'll have to switch nearly all of my
    apps anyway. So using suspend just to save one reboot is not worth
    it (for me) IMHO.

  - I would certainly not keep open documents that are on crypted FS
    while I travel. Otherwise, it would be a total waste of time to
    enter my passphrase everytime I need to access them ! Some might
    argue that it would save me a lot of time, providing me with the
    ability to type my passphrase only once a month, but that's not
    what I'm looking for :-)

I can barely understand why one would prefer to suspend when the notebook
does not move at all, but under the conditions above, advantages are really
faint. I now realize that people I work with also face the same constraints,
which can explain why they don't use such features either, whatever the OS.

Best regards,
Willy

Re: NAK new drivers without proper power management?

[Nigel Cunningham]

Hi.

On Sun, 2007-02-11 at 23:46 +0100, Willy Tarreau wrote:
> > On Sun, 2007-02-11 at 22:52 +0100, Willy Tarreau wrote:
> > > On Sun, Feb 11, 2007 at 12:31:14PM -0600, Robert Hancock wrote:
> > > > Willy Tarreau wrote:
> > > > >Nigel, don't take it as a personal offense, but I think it is a very
> > > > >centric view of Linux usages. Where I work, Linux is used a lot on
> > > > >servers and appliances. It is used for mail relays, HTTP proxies,
> > > > >anti-viruses, firewalls, routers, load balancers, UTM, SSH relays,
> > > > >etc... Nobody would ever want to enable power management on those
> > > > >machines, let alone suspend which would cause a major havoc, would
> > > > >the system decide to enter suspend for any reason.
> > > > >
> > > > >Many people also have Linux on their notebooks, but as a dual-boot. You
> > > > >read the word ? "dual-boot". It means that they cleanly shutdown their
> > > > >system every time they don't use it anymore, and they won't know what
> > > > >OS they'll use next time.
> > > > >
> > > > >I've never heard anyone there complaining "oh, I'm fed up with this
> > > > >boring boot, I always have to wait 30 seconds when I need to do
> > > > >something, I wish I could suspend and resume". It is considered the
> > > > >normal way of using their PCs.
> > > > 
> > > > I think your experience is rather different than that of Joe Average 
> > > > User who doesn't frequent kernel lists, and also I think you'll find 
> > > > that for a lot of Linux laptop users that don't use supend, the reason 
> > > > is that it doesn't work reliably, quite often due to driver issues.
> > > 
> > > I would believe it if I knew people using suspend/resume on the other OS.
> > > But that's not the case either. Also, it happens that with today's RAM
> > > sizes, suspend-to-disk then resume can be several times slower than a
> > > clean fresh boot. When you have 1 GB to write at 20 MB/s, it takes 50
> > > seconds to shut down, and as much to restart. Compare this to 5-10
> > > seconds for a shutdown and 30-50 seconds for a cold boot, and it might
> > > give you another clue why there are people not interested in such a
> > > feature.
> > 
> > I'm using M$ hibernation and Suspend2 to dual boot on our desktop (dtv
> > card that Linux doesn't support well yet), and I know other Suspend2
> > users doing the same. It's made earier by the fact that Suspend2 lets
> > you reboot instead of powering down.
> > 
> > As to comparing the speed with the time to boot, your estimates are way
> > out. Both will of course vary with the harddrive and cpu speeds and
> > compression qualities of the image, but with Suspend2, I'm seeing speeds
> > more in the range of 40-100MB/s, and even had a resport of 160MB/s a
> > couple of days ago. The rule of thumb I use is:
> > 
> > Run hdparm -t (or equiv) on the drive you'll be using:
> > 
> > nigel@nigel:~$ sudo hdparm -t /dev/hda
> > 
> > /dev/hda:
> >  Timing buffered disk reads:  120 MB in  3.02 seconds =  39.70 MB/sec
> > 
> > Then calculate RAM_IN_MB / 2 / HDPARM_RESULT = seconds to read/write
> > image.
> > 
> > In my case: 1024 / 2 / 39.7 = approx 12 seconds. The / 2 is because with
> > LZF compression, you normally get about 50% compression.
> > 
> > I think the mean reason some people aren't interested in suspend to disk
> > is because of myths (if you'll excuse the term) like the one you've put
> > above. Of course that values you give were more accurate for swsusp and
> > uswsusp until recently, but Suspend2 has had async I/O and compression
> > for years, so all I can really do is encourage you to try again.
> 
> Well, I agree that you give some good arguments here.
> 
> > Of course there's another factor you're not taking into account: With
> > suspending to disk, you don't have to close and reopen documents or shut
> > down and restart applications. The time to do that should be factored
> > into the non-suspend-to-disk time to compare apples with apples.
> 
> Hmm sorry, but we don't have the same usages of notebooks. For no reason
> would I keep documents open, for two reasons :
> 
>   - when I shutdown my notebook, it is to move from one customer to
>     home/company/another customer. There's no related work anyway, the
>     network will have changed and I'll have to switch nearly all of my
>     apps anyway. So using suspend just to save one reboot is not worth
>     it (for me) IMHO.

The network configuration utilities can help there. In addition,
Suspend2 preserves the commandline you used to boot with
(/sys/power/suspend2/resume_commandline), so you can use a combination
of slightly varying grub entries (I have one for not starting ath0 and
one for starting it) and scripts to do different things in different
environments. The resume_commandline is writable, so can be cleared
after usage if there were anything sensitive there.

>   - I would certainly not keep open documents that are on crypted FS
>     while I travel. Otherwise, it would be a total waste of time to
>     enter my passphrase everytime I need to access them ! Some might
>     argue that it would save me a lot of time, providing me with the
>     ability to type my passphrase only once a month, but that's not
>     what I'm looking for :-)

People are using Suspend2 with encryption today (I'm not sure about
uswsusp). Some of them have set things up so you need to use a
passphrase or usb key to resume, and the image itself is of course
encrypted too.

You could also close the document and not the app. Or both and just get
the benefit of having the app in page cache post-resume.

> I can barely understand why one would prefer to suspend when the notebook
> does not move at all, but under the conditions above, advantages are really
> faint. I now realize that people I work with also face the same constraints,
> which can explain why they don't use such features either, whatever the OS.

I guess the thing you're highlighting to me is the lack of awareness of
the options that are available. Maybe I need to work harder at making
people aware of the possible usage scenarios! :)

Nigel

Re: NAK new drivers without proper power management?

[Willy Tarreau]

On Mon, Feb 12, 2007 at 10:18:42AM +1100, Nigel Cunningham wrote:
[snip]
> > Hmm sorry, but we don't have the same usages of notebooks. For no reason
> > would I keep documents open, for two reasons :
> > 
> >   - when I shutdown my notebook, it is to move from one customer to
> >     home/company/another customer. There's no related work anyway, the
> >     network will have changed and I'll have to switch nearly all of my
> >     apps anyway. So using suspend just to save one reboot is not worth
> >     it (for me) IMHO.
> 
> The network configuration utilities can help there. In addition,
> Suspend2 preserves the commandline you used to boot with
> (/sys/power/suspend2/resume_commandline), so you can use a combination
> of slightly varying grub entries (I have one for not starting ath0 and
> one for starting it) and scripts to do different things in different
> environments. The resume_commandline is writable, so can be cleared
> after usage if there were anything sensitive there.

OK, I see there are features to make life easier when I decide to use
suspend. But it looks like that using suspend is the goal and dealing
with the constraints is a lot of work and I'm still far from being
convinced that it would provide me advantage.

> >   - I would certainly not keep open documents that are on crypted FS
> >     while I travel. Otherwise, it would be a total waste of time to
> >     enter my passphrase everytime I need to access them ! Some might
> >     argue that it would save me a lot of time, providing me with the
> >     ability to type my passphrase only once a month, but that's not
> >     what I'm looking for :-)
> 
> People are using Suspend2 with encryption today (I'm not sure about
> uswsusp). Some of them have set things up so you need to use a
> passphrase or usb key to resume, and the image itself is of course
> encrypted too.

Unless I'm mistaken, I have to type the passphrase twice then :
  - once at suspend
  - once at resume

which is once more per "boot" than what I'm doing on loop-aes.

> You could also close the document and not the app. Or both and just get
> the benefit of having the app in page cache post-resume.

I'm not much convinced by the advantage of reading 500 MB on disk to have
emacs in hot cache :-)

> > I can barely understand why one would prefer to suspend when the notebook
> > does not move at all, but under the conditions above, advantages are really
> > faint. I now realize that people I work with also face the same constraints,
> > which can explain why they don't use such features either, whatever the OS.
> 
> I guess the thing you're highlighting to me is the lack of awareness of
> the options that are available. Maybe I need to work harder at making
> people aware of the possible usage scenarios! :)

You're certainly right. I really think that this feature is clearly not for
me but it's more featureful than I initially thought, and I could encourage
some people to give it a try.

Best regards,
Willy

Re: NAK new drivers without proper power management?

[Nigel Cunningham]

Hi.

On Mon, 2007-02-12 at 00:38 +0100, Willy Tarreau wrote:
> On Mon, Feb 12, 2007 at 10:18:42AM +1100, Nigel Cunningham wrote:
> [snip]
> > > Hmm sorry, but we don't have the same usages of notebooks. For no reason
> > > would I keep documents open, for two reasons :
> > > 
> > >   - when I shutdown my notebook, it is to move from one customer to
> > >     home/company/another customer. There's no related work anyway, the
> > >     network will have changed and I'll have to switch nearly all of my
> > >     apps anyway. So using suspend just to save one reboot is not worth
> > >     it (for me) IMHO.
> > 
> > The network configuration utilities can help there. In addition,
> > Suspend2 preserves the commandline you used to boot with
> > (/sys/power/suspend2/resume_commandline), so you can use a combination
> > of slightly varying grub entries (I have one for not starting ath0 and
> > one for starting it) and scripts to do different things in different
> > environments. The resume_commandline is writable, so can be cleared
> > after usage if there were anything sensitive there.
> 
> OK, I see there are features to make life easier when I decide to use
> suspend. But it looks like that using suspend is the goal and dealing
> with the constraints is a lot of work and I'm still far from being
> convinced that it would provide me advantage.

Ok. I don't feel like I have to convince everyone :)

> > >   - I would certainly not keep open documents that are on crypted FS
> > >     while I travel. Otherwise, it would be a total waste of time to
> > >     enter my passphrase everytime I need to access them ! Some might
> > >     argue that it would save me a lot of time, providing me with the
> > >     ability to type my passphrase only once a month, but that's not
> > >     what I'm looking for :-)
> > 
> > People are using Suspend2 with encryption today (I'm not sure about
> > uswsusp). Some of them have set things up so you need to use a
> > passphrase or usb key to resume, and the image itself is of course
> > encrypted too.
> 
> Unless I'm mistaken, I have to type the passphrase twice then :
>   - once at suspend
>   - once at resume
> 
> which is once more per "boot" than what I'm doing on loop-aes.

I'm not sure. I don't use encryption myself, so I don't understand all
the fine details. I just know that there are people out there using
encryption, loop-aes, dmsetup and all that sort of stuff. I don't have
to worry about it because they use an initrd/ramfs to do whatever they
need to do to provide access to the device on which the image is found,
then

echo /dev/whatever_funny_device > /sys/power/suspend2/resume2
echo > /sys/power/suspend2/do_resume

> > You could also close the document and not the app. Or both and just get
> > the benefit of having the app in page cache post-resume.
> 
> I'm not much convinced by the advantage of reading 500 MB on disk to have
> emacs in hot cache :-)

Neither am I! Presumably you'd have a lot more than emacs in there
though :) You could always switch to vim! (*ducks*)

Regards,

Nigel

Re: NAK new drivers without proper power management?

[Alan]

> Unless I'm mistaken, I have to type the passphrase twice then :
>   - once at suspend
>   - once at resume
> 
> which is once more per "boot" than what I'm doing on loop-aes.

You don't need to type in a key at suspend time if you don't want to.
Think about gpg email - I can send you an encrypted email without typing
any keys, you need the right key however to read it.

Alan

Re: NAK new drivers without proper power management?

[Willy Tarreau]

On Mon, Feb 12, 2007 at 12:26:52AM +0000, Alan wrote:
> > Unless I'm mistaken, I have to type the passphrase twice then :
> >   - once at suspend
> >   - once at resume
> > 
> > which is once more per "boot" than what I'm doing on loop-aes.
> 
> You don't need to type in a key at suspend time if you don't want to.
> Think about gpg email - I can send you an encrypted email without typing
> any keys, you need the right key however to read it.

OK, so that means that it can generate a random secret which is crypted
with your public key. That's very different from a crypted FS which has
to keep the same secret key over time for obvious reasons, but it is
smart to proceed this way.

One less "myth" as Nigel would say call it ;-)

Thanks Alan for clarifications
Willy

Re: NAK new drivers without proper power management?

[Rafael J. Wysocki]

On Monday, 12 February 2007 06:19, Willy Tarreau wrote:
> On Mon, Feb 12, 2007 at 12:26:52AM +0000, Alan wrote:
> > > Unless I'm mistaken, I have to type the passphrase twice then :
> > >   - once at suspend
> > >   - once at resume
> > > 
> > > which is once more per "boot" than what I'm doing on loop-aes.
> > 
> > You don't need to type in a key at suspend time if you don't want to.
> > Think about gpg email - I can send you an encrypted email without typing
> > any keys, you need the right key however to read it.
> 
> OK, so that means that it can generate a random secret which is crypted
> with your public key. That's very different from a crypted FS which has
> to keep the same secret key over time for obvious reasons, but it is
> smart to proceed this way.
> 
> One less "myth" as Nigel would say call it ;-)

Yup.  Our userland suspend tools available from http://suspend.sf.net are
capable of doing that in a more or less transparent way.

Greetings,
Rafael

Re: NAK new drivers without proper power management?

[Nigel Cunningham]

Hi.

On Mon, 2007-02-12 at 06:19 +0100, Willy Tarreau wrote:
> One less "myth" as Nigel would say call it ;-)

You know me too well! :>

Re: NAK new drivers without proper power management?

[Alan]

> Hmm sorry, but we don't have the same usages of notebooks. For no reason
> would I keep documents open, for two reasons :
> 
>   - when I shutdown my notebook, it is to move from one customer to
>     home/company/another customer. There's no related work anyway, the
>     network will have changed and I'll have to switch nearly all of my
>     apps anyway. So using suspend just to save one reboot is not worth
>     it (for me) IMHO.
> 
>   - I would certainly not keep open documents that are on crypted FS
>     while I travel. 

You use the encryption patches for suspend. And even if you turn your
laptop off and leave it somewhere for a bit I can turn it on install a
trojan and turn it off again.

Suspend/Resume is supposed to work, many people find it useful. One non
suspend friendly driver makes every suspend aware driver on that
system useless so we really should be tight about suspend/resume.

Alan

Re: NAK new drivers without proper power management?

[Rafael J. Wysocki]

On Sunday, 11 February 2007 23:46, Willy Tarreau wrote:
> On Mon, Feb 12, 2007 at 09:26:26AM +1100, Nigel Cunningham wrote:
> > Hi.
> > 
> > On Sun, 2007-02-11 at 22:52 +0100, Willy Tarreau wrote:
> > > On Sun, Feb 11, 2007 at 12:31:14PM -0600, Robert Hancock wrote:
> > > > Willy Tarreau wrote:
> > > > >Nigel, don't take it as a personal offense, but I think it is a very
> > > > >centric view of Linux usages. Where I work, Linux is used a lot on
> > > > >servers and appliances. It is used for mail relays, HTTP proxies,
> > > > >anti-viruses, firewalls, routers, load balancers, UTM, SSH relays,
> > > > >etc... Nobody would ever want to enable power management on those
> > > > >machines, let alone suspend which would cause a major havoc, would
> > > > >the system decide to enter suspend for any reason.
> > > > >
> > > > >Many people also have Linux on their notebooks, but as a dual-boot. You
> > > > >read the word ? "dual-boot". It means that they cleanly shutdown their
> > > > >system every time they don't use it anymore, and they won't know what
> > > > >OS they'll use next time.
> > > > >
> > > > >I've never heard anyone there complaining "oh, I'm fed up with this
> > > > >boring boot, I always have to wait 30 seconds when I need to do
> > > > >something, I wish I could suspend and resume". It is considered the
> > > > >normal way of using their PCs.
> > > > 
> > > > I think your experience is rather different than that of Joe Average 
> > > > User who doesn't frequent kernel lists, and also I think you'll find 
> > > > that for a lot of Linux laptop users that don't use supend, the reason 
> > > > is that it doesn't work reliably, quite often due to driver issues.
> > > 
> > > I would believe it if I knew people using suspend/resume on the other OS.
> > > But that's not the case either. Also, it happens that with today's RAM
> > > sizes, suspend-to-disk then resume can be several times slower than a
> > > clean fresh boot. When you have 1 GB to write at 20 MB/s, it takes 50
> > > seconds to shut down, and as much to restart. Compare this to 5-10
> > > seconds for a shutdown and 30-50 seconds for a cold boot, and it might
> > > give you another clue why there are people not interested in such a
> > > feature.

I use the suspend to disk on a regular basis, because it takes at least 3x more
time to boot and get KDE started than to resume.

> > I'm using M$ hibernation and Suspend2 to dual boot on our desktop (dtv
> > card that Linux doesn't support well yet), and I know other Suspend2
> > users doing the same. It's made earier by the fact that Suspend2 lets
> > you reboot instead of powering down.
> > 
> > As to comparing the speed with the time to boot, your estimates are way
> > out. Both will of course vary with the harddrive and cpu speeds and
> > compression qualities of the image, but with Suspend2, I'm seeing speeds
> > more in the range of 40-100MB/s, and even had a resport of 160MB/s a
> > couple of days ago. The rule of thumb I use is:
> > 
> > Run hdparm -t (or equiv) on the drive you'll be using:
> > 
> > nigel@nigel:~$ sudo hdparm -t /dev/hda
> > 
> > /dev/hda:
> >  Timing buffered disk reads:  120 MB in  3.02 seconds =  39.70 MB/sec
> > 
> > Then calculate RAM_IN_MB / 2 / HDPARM_RESULT = seconds to read/write
> > image.
> > 
> > In my case: 1024 / 2 / 39.7 = approx 12 seconds. The / 2 is because with
> > LZF compression, you normally get about 50% compression.
> > 
> > I think the mean reason some people aren't interested in suspend to disk
> > is because of myths (if you'll excuse the term) like the one you've put
> > above. Of course that values you give were more accurate for swsusp and
> > uswsusp until recently, but Suspend2 has had async I/O and compression
> > for years, so all I can really do is encourage you to try again.
> 
> Well, I agree that you give some good arguments here.
> 
> > Of course there's another factor you're not taking into account: With
> > suspending to disk, you don't have to close and reopen documents or shut
> > down and restart applications. The time to do that should be factored
> > into the non-suspend-to-disk time to compare apples with apples.
> 
> Hmm sorry, but we don't have the same usages of notebooks. For no reason
> would I keep documents open, for two reasons :
> 
>   - when I shutdown my notebook, it is to move from one customer to
>     home/company/another customer. There's no related work anyway, the
>     network will have changed and I'll have to switch nearly all of my
>     apps anyway. So using suspend just to save one reboot is not worth
>     it (for me) IMHO.
> 
>   - I would certainly not keep open documents that are on crypted FS
>     while I travel. Otherwise, it would be a total waste of time to
>     enter my passphrase everytime I need to access them ! Some might
>     argue that it would save me a lot of time, providing me with the
>     ability to type my passphrase only once a month, but that's not
>     what I'm looking for :-)
> 
> I can barely understand why one would prefer to suspend when the notebook
> does not move at all, but under the conditions above, advantages are really
> faint. I now realize that people I work with also face the same constraints,
> which can explain why they don't use such features either, whatever the OS.

Please note we're talking about the suspend to RAM here too and, arguably, the
support in drivers is more important for the suspend to RAM.

Greetings,
Rafael

Re: NAK new drivers without proper power management?

[Rafael J. Wysocki]

On Sunday, 11 February 2007 23:26, Nigel Cunningham wrote:
> Hi.
> 
> On Sun, 2007-02-11 at 22:52 +0100, Willy Tarreau wrote:
> > On Sun, Feb 11, 2007 at 12:31:14PM -0600, Robert Hancock wrote:
> > > Willy Tarreau wrote:
> > > >Nigel, don't take it as a personal offense, but I think it is a very
> > > >centric view of Linux usages. Where I work, Linux is used a lot on
> > > >servers and appliances. It is used for mail relays, HTTP proxies,
> > > >anti-viruses, firewalls, routers, load balancers, UTM, SSH relays,
> > > >etc... Nobody would ever want to enable power management on those
> > > >machines, let alone suspend which would cause a major havoc, would
> > > >the system decide to enter suspend for any reason.
> > > >
> > > >Many people also have Linux on their notebooks, but as a dual-boot. You
> > > >read the word ? "dual-boot". It means that they cleanly shutdown their
> > > >system every time they don't use it anymore, and they won't know what
> > > >OS they'll use next time.
> > > >
> > > >I've never heard anyone there complaining "oh, I'm fed up with this
> > > >boring boot, I always have to wait 30 seconds when I need to do
> > > >something, I wish I could suspend and resume". It is considered the
> > > >normal way of using their PCs.
> > > 
> > > I think your experience is rather different than that of Joe Average 
> > > User who doesn't frequent kernel lists, and also I think you'll find 
> > > that for a lot of Linux laptop users that don't use supend, the reason 
> > > is that it doesn't work reliably, quite often due to driver issues.
> > 
> > I would believe it if I knew people using suspend/resume on the other OS.
> > But that's not the case either. Also, it happens that with today's RAM
> > sizes, suspend-to-disk then resume can be several times slower than a
> > clean fresh boot. When you have 1 GB to write at 20 MB/s, it takes 50
> > seconds to shut down, and as much to restart. Compare this to 5-10
> > seconds for a shutdown and 30-50 seconds for a cold boot, and it might
> > give you another clue why there are people not interested in such a
> > feature.
> 
> I'm using M$ hibernation and Suspend2 to dual boot on our desktop (dtv
> card that Linux doesn't support well yet), and I know other Suspend2
> users doing the same. It's made earier by the fact that Suspend2 lets
> you reboot instead of powering down.

Well, I don't know why you're saying it's a special capability of suspend2.
Even the "old" swsusp has been able to do this since I can remember. ;-)

Greetings,
Rafael

Re: NAK new drivers without proper power management?

[Nigel Cunningham]

Hi.

On Mon, 2007-02-12 at 00:41 +0100, Rafael J. Wysocki wrote:
> > I'm using M$ hibernation and Suspend2 to dual boot on our desktop (dtv
> > card that Linux doesn't support well yet), and I know other Suspend2
> > users doing the same. It's made earier by the fact that Suspend2 lets
> > you reboot instead of powering down.
> 
> Well, I don't know why you're saying it's a special capability of suspend2.
> Even the "old" swsusp has been able to do this since I can remember. ;-)

It does?! I just did cat /sys/power/disk and it only says platform. How
do you make swsusp reboot instead of powering down?

Regards,

Nigel

Re: NAK new drivers without proper power management?

[Rafael J. Wysocki]

On Monday, 12 February 2007 00:47, Nigel Cunningham wrote:
> Hi.
> 
> On Mon, 2007-02-12 at 00:41 +0100, Rafael J. Wysocki wrote:
> > > I'm using M$ hibernation and Suspend2 to dual boot on our desktop (dtv
> > > card that Linux doesn't support well yet), and I know other Suspend2
> > > users doing the same. It's made earier by the fact that Suspend2 lets
> > > you reboot instead of powering down.
> > 
> > Well, I don't know why you're saying it's a special capability of suspend2.
> > Even the "old" swsusp has been able to do this since I can remember. ;-)
> 
> It does?! I just did cat /sys/power/disk and it only says platform. How
> do you make swsusp reboot instead of powering down?

echo reboot > /sys/power/disk && echo disk > /sys/power/state

Greetings,
Rafael

Re: NAK new drivers without proper power management?

[Nigel Cunningham]

Hi.

On Mon, 2007-02-12 at 00:50 +0100, Rafael J. Wysocki wrote:
> On Monday, 12 February 2007 00:47, Nigel Cunningham wrote:
> > Hi.
> > 
> > On Mon, 2007-02-12 at 00:41 +0100, Rafael J. Wysocki wrote:
> > > > I'm using M$ hibernation and Suspend2 to dual boot on our desktop (dtv
> > > > card that Linux doesn't support well yet), and I know other Suspend2
> > > > users doing the same. It's made earier by the fact that Suspend2 lets
> > > > you reboot instead of powering down.
> > > 
> > > Well, I don't know why you're saying it's a special capability of suspend2.
> > > Even the "old" swsusp has been able to do this since I can remember. ;-)
> > 
> > It does?! I just did cat /sys/power/disk and it only says platform. How
> > do you make swsusp reboot instead of powering down?
> 
> echo reboot > /sys/power/disk && echo disk > /sys/power/state

Ah. Perhaps you should make it show reboot when you cat it?

Regards,

Nigel

Re: NAK new drivers without proper power management?

[Rafael J. Wysocki]

On Monday, 12 February 2007 00:55, Nigel Cunningham wrote:
> Hi.
> 
> On Mon, 2007-02-12 at 00:50 +0100, Rafael J. Wysocki wrote:
> > On Monday, 12 February 2007 00:47, Nigel Cunningham wrote:
> > > Hi.
> > > 
> > > On Mon, 2007-02-12 at 00:41 +0100, Rafael J. Wysocki wrote:
> > > > > I'm using M$ hibernation and Suspend2 to dual boot on our desktop (dtv
> > > > > card that Linux doesn't support well yet), and I know other Suspend2
> > > > > users doing the same. It's made earier by the fact that Suspend2 lets
> > > > > you reboot instead of powering down.
> > > > 
> > > > Well, I don't know why you're saying it's a special capability of suspend2.
> > > > Even the "old" swsusp has been able to do this since I can remember. ;-)
> > > 
> > > It does?! I just did cat /sys/power/disk and it only says platform. How
> > > do you make swsusp reboot instead of powering down?
> > 
> > echo reboot > /sys/power/disk && echo disk > /sys/power/state
> 
> Ah. Perhaps you should make it show reboot when you cat it?

albercik:~ # echo reboot > /sys/power/disk
albercik:~ # cat /sys/power/disk
reboot

It shows the current value, and "platform" happens to be the default now.

Greetings,
Rafael

Re: NAK new drivers without proper power management?

[Nigel Cunningham]

Hi.

On Mon, 2007-02-12 at 01:09 +0100, Rafael J. Wysocki wrote:
> On Monday, 12 February 2007 00:55, Nigel Cunningham wrote:
> > Hi.
> > 
> > On Mon, 2007-02-12 at 00:50 +0100, Rafael J. Wysocki wrote:
> > > On Monday, 12 February 2007 00:47, Nigel Cunningham wrote:
> > > > Hi.
> > > > 
> > > > On Mon, 2007-02-12 at 00:41 +0100, Rafael J. Wysocki wrote:
> > > > > > I'm using M$ hibernation and Suspend2 to dual boot on our desktop (dtv
> > > > > > card that Linux doesn't support well yet), and I know other Suspend2
> > > > > > users doing the same. It's made earier by the fact that Suspend2 lets
> > > > > > you reboot instead of powering down.
> > > > > 
> > > > > Well, I don't know why you're saying it's a special capability of suspend2.
> > > > > Even the "old" swsusp has been able to do this since I can remember. ;-)
> > > > 
> > > > It does?! I just did cat /sys/power/disk and it only says platform. How
> > > > do you make swsusp reboot instead of powering down?
> > > 
> > > echo reboot > /sys/power/disk && echo disk > /sys/power/state
> > 
> > Ah. Perhaps you should make it show reboot when you cat it?
> 
> albercik:~ # echo reboot > /sys/power/disk
> albercik:~ # cat /sys/power/disk
> reboot
> 
> It shows the current value, and "platform" happens to be the default now.

Oh, so the problem is that it shows the current value, not the
possibilities. I wrongly assumed it would work like /sys/power/disk.
That explains it :)

Regards,

Nigel

Re: NAK new drivers without proper power management?

[Pavel Machek]

Hi!

> > I think your experience is rather different than that of Joe Average 
> > User who doesn't frequent kernel lists, and also I think you'll find 
> > that for a lot of Linux laptop users that don't use supend, the reason 
> > is that it doesn't work reliably, quite often due to driver issues.
> 
> I would believe it if I knew people using suspend/resume on the other OS.
> But that's not the case either. Also, it happens that with today's RAM
> sizes, suspend-to-disk then resume can be several times slower than a
> clean fresh boot. When you have 1 GB to write at 20 MB/s, it takes 50

Stop spreading FUD. swsusp only saves _used_ memory, not all memory,
so it indeed should be faster these days. And yes, it supports
encryption these days.

						Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

Re: NAK new drivers without proper power management?

[Robert Hancock]

Tilman Schmidt wrote:
>>>> If your device requires power management, and you know it requires power
>>>> management, why not just implement power management? [...]
>>> Like it or not, power management is far from trivial, and people
>>> writing device drivers have limited resources. [...]
>> It's not that complex. All we're really talking about is a bit of extra
>> code to cleanup and configure hardware state; things that the driver
>> author already knows how to do. S3 might require a bit more
>> initialisation if firmware needs to be reloaded or more extensive
>> configuration needs to be done, but if there's firmware to be loaded,
>> there is a reasonably good probability that we loaded it from Linux to
>> start with anyway.
> 
> You are assuming a perfect world where driver authors have complete
> knowledge of their devices. In reality, many drivers (including
> those I have the mixed pleasure of maintaining) are based at least
> in part on reverse engineering, and managing power states may well
> fall into the domain of things not yet sufficiently reverse
> engineered.
> 
>>> Also, in your argument you neglected a few cases:
>>> - What if my device does not require power management?
>> Then you as a generic routine that does nothing but return success
>> (potentially shared with other drivers that are in the same situation).
> 
> But if I just write an empty routine like that I open myself up to
> criticism along the lines of "writing dummy routines just in order
> to shut up kernel warnings". BTDT.

Well, it couldn't actually be an empty routine (at least not for a PCI 
device), since the generic PCI suspend/resume handling doesn't get 
called if you have suspend/resume functions defined, so you'd have to do 
the pci_save_state, pci_disable_device, pci_set_power_state, etc. in 
there at least. Using empty functions would prevent those from being 
called and result in your PCI config space contain crap after resuming, 
which can break the whole system.

That's a bit messy, actually.. I know we can't just do that stuff 
unconditionally in the PCI layer since some devices blow up if you 
disable them, which we normally do, etc. We should just have some 
generic function you can stick in the .suspend slot that just says "I 
know how to suspend, but don't need anything more than the generic 
handling". And if you do need more than that (which is almost always the 
case), you can just call that from your own function and then add what 
you need, instead of duplicating the code a million times (sometimes in 
an incomplete/incorrect fashion) like we do now.

>>> - What if I don't know whether my device requires power management?
>> The questions are straight forward: Is there hardware state that needs
>> to be configured if you've just booted the computer and nothing else has
>> touched it? If so, that needs to be done in a resume method. Do you need
>> to clean up state prior to doing the things in the resume method, or
>> otherwise do things to quiesce the driver? If so, they will need to be
>> done in the suspend method. The result will be roughly similar to what
>> you do for module load/unload, except maybe less complete in some cases.
> 
> I don't doubt your basic assessment. However it doesn't translate that
> easily into a real implementation. In my case, I maintain a USB driver,
> so I have to deal with USB specifics of suspend/resume which happen not
> to be that well documented. My driver provides an isdn4linux device but
> isdn4linux knows nothing about suspend/resume so I am on my own on how
> to reconcile the two. The device itself, though in turn far from trivial,
> is actually the least of my worries.

That is one good excuse for not implementing it - the driver is part of 
a framework which does not handle suspend/resume itself. (The current 
FireWire stack is another case like this.) This is the kind of situation 
where I would say the driver should just define a suspend function that 
returns -ENOSYS and then the user would know they have to remove that 
module, etc. before suspending (there is at least some distro script 
support for doing that automatically based on a config file), since it 
hasn't a hope of working after resume until the framework is updated to 
support suspending.

-- 
Robert Hancock      Saskatoon, SK, Canada
To email, remove "nospam" from hancockr@nospamshaw.ca
Home Page: http://www.roberthancock.com/