Re: NAK new drivers without proper power management?

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
> -
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> 
> 

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

[PATCH] Re: NAK new drivers without proper power management?

[Nigel Cunningham]

Hi.

On Fri, 2007-02-09 at 19:50 -0600, Robert Hancock wrote:
> 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.

Here's my current version of a patch to do this, if anyone wants to try
it out. It dumps stack with the warning to make it easier to see what
the source of the message is:

 drivers/base/core.c       |   25 +++++++++++++++++++++++++
 drivers/pci/pci-driver.c  |    6 ++++++
 drivers/usb/core/driver.c |    5 +++++
 include/linux/device.h    |    1 +
 4 files changed, 37 insertions(+)
diff -ruNp 920-report-no-pm-support.patch-old/drivers/base/core.c 920-report-no-pm-support.patch-new/drivers/base/core.c
--- 920-report-no-pm-support.patch-old/drivers/base/core.c	2007-02-06 14:48:31.000000000 +1100
+++ 920-report-no-pm-support.patch-new/drivers/base/core.c	2007-02-10 13:36:33.000000000 +1100
@@ -552,6 +552,30 @@ int device_add(struct device *dev)
 				class_intf->add_dev(dev, class_intf);
 		up(&dev->class->sem);
 	}
+
+#ifdef CONFIG_PM
+	{
+	int nosusp = 0, nores = 0;
+
+	if (!((dev->class && dev->class->suspend) ||
+	      (dev->bus && (dev->bus->suspend || dev->bus->suspend_late))))
+		nosusp = 1;
+
+	if (!((dev->class && dev->class->resume) ||
+	      (dev->bus && (dev->bus->resume || dev->bus->resume_early))))
+		nores = 1;
+
+	if ((nosusp || nores) && !dev->pm_safe) {
+		printk("Device driver %s lacks bus and class support for "
+				"being %s.\n",
+			kobject_name(&dev->kobj),
+			nosusp ? (nores ? "suspended or resumed" :
+				"resumed") : "suspended");
+		dump_stack();
+	}
+	}
+#endif
+
  Done:
  	kfree(class_name);
 	put_device(dev);
@@ -851,6 +875,7 @@ struct device *device_create(struct clas
 	dev->class = class;
 	dev->parent = parent;
 	dev->release = device_create_release;
+	dev->pm_safe = 1;
 
 	va_start(args, fmt);
 	vsnprintf(dev->bus_id, BUS_ID_SIZE, fmt, args);
diff -ruNp 920-report-no-pm-support.patch-old/drivers/pci/pci-driver.c 920-report-no-pm-support.patch-new/drivers/pci/pci-driver.c
--- 920-report-no-pm-support.patch-old/drivers/pci/pci-driver.c	2007-02-06 14:48:44.000000000 +1100
+++ 920-report-no-pm-support.patch-new/drivers/pci/pci-driver.c	2007-02-10 14:00:39.000000000 +1100
@@ -449,6 +449,12 @@ int __pci_register_driver(struct pci_dri
 	if (error)
 		driver_unregister(&drv->driver);
 
+	if (!drv->suspend || !drv->resume)
+		printk("PCI driver %s lacks driver specific %s support.\n",
+				drv->name,
+				!drv->suspend ? (drv->resume ? "suspend" :
+					"suspend and resume") :	"resume");
+
 	return error;
 }
 
diff -ruNp 920-report-no-pm-support.patch-old/drivers/usb/core/driver.c 920-report-no-pm-support.patch-new/drivers/usb/core/driver.c
--- 920-report-no-pm-support.patch-old/drivers/usb/core/driver.c	2007-02-06 14:48:47.000000000 +1100
+++ 920-report-no-pm-support.patch-new/drivers/usb/core/driver.c	2007-02-10 12:32:57.000000000 +1100
@@ -709,6 +709,11 @@ int usb_register_device_driver(struct us
 		pr_info("%s: registered new device driver %s\n",
 			usbcore_name, new_udriver->name);
 		usbfs_update_special();
+		if (!new_udriver->suspend || !new_udriver->resume)
+			printk("USB driver %s lacks %s support.\n",
+				new_udriver->name, !new_udriver->suspend ?
+				(new_udriver->resume ? "suspend" :
+				 "suspend and resume") : "resume");
 	} else {
 		printk(KERN_ERR "%s: error %d registering device "
 			"	driver %s\n",
diff -ruNp 920-report-no-pm-support.patch-old/include/linux/device.h 920-report-no-pm-support.patch-new/include/linux/device.h
--- 920-report-no-pm-support.patch-old/include/linux/device.h	2007-02-06 14:48:56.000000000 +1100
+++ 920-report-no-pm-support.patch-new/include/linux/device.h	2007-02-10 13:36:01.000000000 +1100
@@ -356,6 +356,7 @@ struct device {
 	struct kobject kobj;
 	char	bus_id[BUS_ID_SIZE];	/* position on parent bus */
 	unsigned		is_registered:1;
+	unsigned		pm_safe:1; /* No suspend/resume fns ok? */
 	struct device_attribute uevent_attr;
 	struct device_attribute *devt_attr;
 
 


My output:
nigel@nigel:~$ dmesg | grep lacks
[   15.113674] Device driver platform lacks bus and class support for being suspended or resumed.
[   15.131601] Device driver pci0000:00 lacks bus and class support for being suspended or resumed.
[   15.179802] Device driver pnp0 lacks bus and class support for being suspended or resumed.
[   15.972661] Device driver ide0 lacks bus and class support for being suspended or resumed.
[   17.829746] Device driver ide1 lacks bus and class support for being suspended or resumed.
[   17.830878] PCI driver ALI15x3_IDE lacks driver specific suspend and resume support.
[   17.830963] PCI driver PIIX_IDE lacks driver specific suspend and resume support.
[   17.878190] Device driver serio0 lacks bus and class support for being resumed.
[   17.878442] Device driver serio1 lacks bus and class support for being resumed.
[   17.878672] Device driver serio2 lacks bus and class support for being resumed.
[   18.555856] Device driver serio3 lacks bus and class support for being resumed.
[   18.558109] Device driver serio4 lacks bus and class support for being resumed.
[   78.487717] Device driver usbdev1.1_ep00 lacks bus and class support for being suspended or resumed.
[   78.595362] Device driver usbdev1.1_ep81 lacks bus and class support for being suspended or resumed.
[   78.657382] Device driver usbdev2.1_ep00 lacks bus and class support for being suspended or resumed.
[   78.765044] Device driver usbdev2.1_ep81 lacks bus and class support for being suspended or resumed.
[   78.795324] Device driver usbdev3.1_ep00 lacks bus and class support for being suspended or resumed.
[   78.904912] Device driver usbdev3.1_ep81 lacks bus and class support for being suspended or resumed.
[   78.936997] PCI driver ali15x3_smbus lacks driver specific suspend and resume support.
[   78.996318] PCI driver ali1535_smbus lacks driver specific suspend and resume support.

Re: [PATCH] Re: NAK new drivers without proper power management?

[Rafael J. Wysocki]

Hi,

On Saturday, 10 February 2007 04:02, Nigel Cunningham wrote:
> Hi.
> 
> On Fri, 2007-02-09 at 19:50 -0600, Robert Hancock wrote:
> > 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.
> 
> Here's my current version of a patch to do this, if anyone wants to try
> it out. It dumps stack with the warning to make it easier to see what
> the source of the message is:

I have an alternative idea.

There is a test mode of swsusp that's triggered with
"echo test > /sys/power/disk" and "echo disk > /sys/power/state".  We can make
it set a switch that will be used to trigger the warnings in the core.

This way the warnings will only appear in the user's dmesg in the test mode
and not always.

Would that be acceptable?

Rafael

Re: [PATCH] Re: NAK new drivers without proper power management?

[Rafael J. Wysocki]

Hi,

On Saturday, 10 February 2007 04:02, Nigel Cunningham wrote:
> Hi.
> 
> On Fri, 2007-02-09 at 19:50 -0600, Robert Hancock wrote:
> > 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.
> 
> Here's my current version of a patch to do this, if anyone wants to try
> it out. It dumps stack with the warning to make it easier to see what
> the source of the message is:

I have an alternative idea.

There is a test mode of swsusp that's triggered with
"echo test > /sys/power/disk" and "echo disk > /sys/power/state".  We can make
it set a switch that will be used to trigger the warnings in the core.

This way the warnings will only appear in the user's dmesg in the test mode
and not always.

Would that be acceptable?

Rafael

Re: [PATCH] Re: NAK new drivers without proper power management?

[Nigel Cunningham]

Gidday.

On Sat, 2007-02-10 at 10:34 +0100, Rafael J. Wysocki wrote:
> On Saturday, 10 February 2007 04:02, Nigel Cunningham wrote:
> > On Fri, 2007-02-09 at 19:50 -0600, Robert Hancock wrote:
> > > 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.
> > 
> > Here's my current version of a patch to do this, if anyone wants to try
> > it out. It dumps stack with the warning to make it easier to see what
> > the source of the message is:
> 
> I have an alternative idea.
> 
> There is a test mode of swsusp that's triggered with
> "echo test > /sys/power/disk" and "echo disk > /sys/power/state".  We can make
> it set a switch that will be used to trigger the warnings in the core.
> 
> This way the warnings will only appear in the user's dmesg in the test mode
> and not always.
> 
> Would that be acceptable?

Well, the original desire was to stop new drivers getting in without
proper power management. For this to help achieve that aim, one or more
of the following would need to happen:

* developers of new drivers would have to remember to run the test
after/during writing their driver. Of course if they remember to do
this, they've already remembered that they need to implement power
management;
* you, I or someone else would need to test all these trees before
Andrew and Linus merge them and report problems to the developers before
they get their new drivers merged;
* Andrew or Linus would run it prior to or after merging a whole lot of
stuff.

I'm afraid I don't like the chances of any of those things happening, so
I'm not sure that it is an acceptable alternative from my perspective. 

Sticking a printk in dmesg doesn't exactly put the problem in flashing
red 36 point characters before the developer either, but I think they're
slightly more likely to see it there if only because they might stick
printks in that they want to read (eg perhaps while debugging the
driver) and therefore see the message when checking output from the
driver being loaded/initialised.

Maybe another alternative would be to make the warnings compile time
warnings - if that's possible?

Regards,

Nigel

Re: [PATCH] Re: NAK new drivers without proper power management?

[Rafael J. Wysocki]

Hi,

On Saturday, 10 February 2007 11:02, Nigel Cunningham wrote:
> Gidday.
> 
> On Sat, 2007-02-10 at 10:34 +0100, Rafael J. Wysocki wrote:
> > On Saturday, 10 February 2007 04:02, Nigel Cunningham wrote:
> > > On Fri, 2007-02-09 at 19:50 -0600, Robert Hancock wrote:
> > > > 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.
> > > 
> > > Here's my current version of a patch to do this, if anyone wants to try
> > > it out. It dumps stack with the warning to make it easier to see what
> > > the source of the message is:
> > 
> > I have an alternative idea.
> > 
> > There is a test mode of swsusp that's triggered with
> > "echo test > /sys/power/disk" and "echo disk > /sys/power/state".  We can make
> > it set a switch that will be used to trigger the warnings in the core.
> > 
> > This way the warnings will only appear in the user's dmesg in the test mode
> > and not always.
> > 
> > Would that be acceptable?
> 
> Well, the original desire was to stop new drivers getting in without
> proper power management.

I know, but I agree with the argument that having a driver without the
suspend/resume support is better than not having the driver at all.
Moreover, if you _know_ which of the drivers you use have no suspend/resume
support, usually you _can_ suspend (at least to disk) and resume anyway - you
only need to unload their modules before the suspend.  Of course, this is not
true for the disk (and related) drivers and for the drivers that cannot be
unloaded.  [I think it generally is not true for the suspend-to-RAM either.]

Also, I think there are quite some drivers already in the tree that don't
support suspend/resume explicitly and honestly we should start from adding the
suspend/resume routines to these drivers _before_ we ban new drivers like that.

> For this to help achieve that aim, one or more 
> of the following would need to happen:
> 
> * developers of new drivers would have to remember to run the test
> after/during writing their driver. Of course if they remember to do
> this, they've already remembered that they need to implement power
> management;
> * you, I or someone else would need to test all these trees before
> Andrew and Linus merge them and report problems to the developers before
> they get their new drivers merged;
> * Andrew or Linus would run it prior to or after merging a whole lot of
> stuff.
> 
> I'm afraid I don't like the chances of any of those things happening, so
> I'm not sure that it is an acceptable alternative from my perspective. 
> 
> Sticking a printk in dmesg doesn't exactly put the problem in flashing
> red 36 point characters before the developer either, but I think they're
> slightly more likely to see it there if only because they might stick
> printks in that they want to read (eg perhaps while debugging the
> driver) and therefore see the message when checking output from the
> driver being loaded/initialised.
> 
> Maybe another alternative would be to make the warnings compile time
> warnings - if that's possible?

Well, maybe.

Still, I'd like to create standard debugging procedures for suspend/resume, so
that if someone reports a problem, we can tell him exactly what to do next.
>From this point of view, the idea of having warnings related to the lack of
.suspend or .resume routines in drivers that will appear in the user's dmesg in
the test mode seems to be a good one. ;-)

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: [PATCH] Re: NAK new drivers without proper power management?

[Rafael J. Wysocki]

Hi,

On Saturday, 10 February 2007 11:02, Nigel Cunningham wrote:
> Gidday.
> 
> On Sat, 2007-02-10 at 10:34 +0100, Rafael J. Wysocki wrote:
> > On Saturday, 10 February 2007 04:02, Nigel Cunningham wrote:
> > > On Fri, 2007-02-09 at 19:50 -0600, Robert Hancock wrote:
> > > > 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.
> > > 
> > > Here's my current version of a patch to do this, if anyone wants to try
> > > it out. It dumps stack with the warning to make it easier to see what
> > > the source of the message is:
> > 
> > I have an alternative idea.
> > 
> > There is a test mode of swsusp that's triggered with
> > "echo test > /sys/power/disk" and "echo disk > /sys/power/state".  We can make
> > it set a switch that will be used to trigger the warnings in the core.
> > 
> > This way the warnings will only appear in the user's dmesg in the test mode
> > and not always.
> > 
> > Would that be acceptable?
> 
> Well, the original desire was to stop new drivers getting in without
> proper power management.

I know, but I agree with the argument that having a driver without the
suspend/resume support is better than not having the driver at all.
Moreover, if you _know_ which of the drivers you use have no suspend/resume
support, usually you _can_ suspend (at least to disk) and resume anyway - you
only need to unload their modules before the suspend.  Of course, this is not
true for the disk (and related) drivers and for the drivers that cannot be
unloaded.  [I think it generally is not true for the suspend-to-RAM either.]

Also, I think there are quite some drivers already in the tree that don't
support suspend/resume explicitly and honestly we should start from adding the
suspend/resume routines to these drivers _before_ we ban new drivers like that.

> For this to help achieve that aim, one or more 
> of the following would need to happen:
> 
> * developers of new drivers would have to remember to run the test
> after/during writing their driver. Of course if they remember to do
> this, they've already remembered that they need to implement power
> management;
> * you, I or someone else would need to test all these trees before
> Andrew and Linus merge them and report problems to the developers before
> they get their new drivers merged;
> * Andrew or Linus would run it prior to or after merging a whole lot of
> stuff.
> 
> I'm afraid I don't like the chances of any of those things happening, so
> I'm not sure that it is an acceptable alternative from my perspective. 
> 
> Sticking a printk in dmesg doesn't exactly put the problem in flashing
> red 36 point characters before the developer either, but I think they're
> slightly more likely to see it there if only because they might stick
> printks in that they want to read (eg perhaps while debugging the
> driver) and therefore see the message when checking output from the
> driver being loaded/initialised.
> 
> Maybe another alternative would be to make the warnings compile time
> warnings - if that's possible?

Well, maybe.

Still, I'd like to create standard debugging procedures for suspend/resume, so
that if someone reports a problem, we can tell him exactly what to do next.
>From this point of view, the idea of having warnings related to the lack of
.suspend or .resume routines in drivers that will appear in the user's dmesg in
the test mode seems to be a good one. ;-)

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: [PATCH] Re: NAK new drivers without proper power management?

[Daniel Barkalow]

On Sat, 10 Feb 2007, Rafael J. Wysocki wrote:

> On Saturday, 10 February 2007 11:02, Nigel Cunningham wrote:
>
> > Well, the original desire was to stop new drivers getting in without
> > proper power management.
> 
> I know, but I agree with the argument that having a driver without the
> suspend/resume support is better than not having the driver at all.

How about if "proper power management" is defined to include the driver 
explicitly preventing suspend? It seems to me like the current problem is 
that driver writers don't think about power management at all, and the 
result is that, after suspend/resume, the system doesn't come back. It 
would be better if driver writers had to think about power management just 
enough to realize that it's not going to work, and make this information 
available to the system. At that point, it's relatively easy for the 
system to do something useful about it.

> Also, I think there are quite some drivers already in the tree that don't
> support suspend/resume explicitly and honestly we should start from adding the
> suspend/resume routines to these drivers _before_ we ban new drivers like that.

It'd be relatively quick to modify all the current drivers that don't 
explicitly support suspend/resume to explicitly not support it. (Or to 
explicitly support it trivially; /dev/null obviously doesn't need 
anything.)

	-Daniel
*This .sig left intentionally blank*

Re: [PATCH] Re: NAK new drivers without proper power management?

[Daniel Barkalow]

On Sat, 10 Feb 2007, Rafael J. Wysocki wrote:

> On Saturday, 10 February 2007 11:02, Nigel Cunningham wrote:
>
> > Well, the original desire was to stop new drivers getting in without
> > proper power management.
> 
> I know, but I agree with the argument that having a driver without the
> suspend/resume support is better than not having the driver at all.

How about if "proper power management" is defined to include the driver 
explicitly preventing suspend? It seems to me like the current problem is 
that driver writers don't think about power management at all, and the 
result is that, after suspend/resume, the system doesn't come back. It 
would be better if driver writers had to think about power management just 
enough to realize that it's not going to work, and make this information 
available to the system. At that point, it's relatively easy for the 
system to do something useful about it.

> Also, I think there are quite some drivers already in the tree that don't
> support suspend/resume explicitly and honestly we should start from adding the
> suspend/resume routines to these drivers _before_ we ban new drivers like that.

It'd be relatively quick to modify all the current drivers that don't 
explicitly support suspend/resume to explicitly not support it. (Or to 
explicitly support it trivially; /dev/null obviously doesn't need 
anything.)

	-Daniel
*This .sig left intentionally blank*

Re: [PATCH] Re: NAK new drivers without proper power management?

[Rafael J. Wysocki]

On Saturday, 10 February 2007 18:52, Daniel Barkalow wrote:
> On Sat, 10 Feb 2007, Rafael J. Wysocki wrote:
> 
> > On Saturday, 10 February 2007 11:02, Nigel Cunningham wrote:
> >
> > > Well, the original desire was to stop new drivers getting in without
> > > proper power management.
> > 
> > I know, but I agree with the argument that having a driver without the
> > suspend/resume support is better than not having the driver at all.
> 
> How about if "proper power management" is defined to include the driver 
> explicitly preventing suspend? It seems to me like the current problem is 
> that driver writers don't think about power management at all, and the 
> result is that, after suspend/resume, the system doesn't come back. It 
> would be better if driver writers had to think about power management just 
> enough to realize that it's not going to work, and make this information 
> available to the system. At that point, it's relatively easy for the 
> system to do something useful about it.

Actually, it is easy for the driver authors to do this right now.  They can
just make the .suspend() routine always return an error.

Well, I think this is a good idea: if the device in question requires specific
power management during the suspend/resume, but it is not implemented by the
driver, we should require the author of the driver to define the .suspend()
routine that returns -ENOSYS (preferably, with an explanatory warning in
dmesg).

Thoughts?

> > Also, I think there are quite some drivers already in the tree that don't
> > support suspend/resume explicitly and honestly we should start from adding the
> > suspend/resume routines to these drivers _before_ we ban new drivers like that.
> 
> It'd be relatively quick to modify all the current drivers that don't 
> explicitly support suspend/resume to explicitly not support it. (Or to 
> explicitly support it trivially; /dev/null obviously doesn't need 
> anything.)

The problem is we have to review quite a lot of drivers for this purpose.
Still it looks like we should do this anyway.

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: [PATCH] Re: NAK new drivers without proper power management?

[Rafael J. Wysocki]

On Saturday, 10 February 2007 18:52, Daniel Barkalow wrote:
> On Sat, 10 Feb 2007, Rafael J. Wysocki wrote:
> 
> > On Saturday, 10 February 2007 11:02, Nigel Cunningham wrote:
> >
> > > Well, the original desire was to stop new drivers getting in without
> > > proper power management.
> > 
> > I know, but I agree with the argument that having a driver without the
> > suspend/resume support is better than not having the driver at all.
> 
> How about if "proper power management" is defined to include the driver 
> explicitly preventing suspend? It seems to me like the current problem is 
> that driver writers don't think about power management at all, and the 
> result is that, after suspend/resume, the system doesn't come back. It 
> would be better if driver writers had to think about power management just 
> enough to realize that it's not going to work, and make this information 
> available to the system. At that point, it's relatively easy for the 
> system to do something useful about it.

Actually, it is easy for the driver authors to do this right now.  They can
just make the .suspend() routine always return an error.

Well, I think this is a good idea: if the device in question requires specific
power management during the suspend/resume, but it is not implemented by the
driver, we should require the author of the driver to define the .suspend()
routine that returns -ENOSYS (preferably, with an explanatory warning in
dmesg).

Thoughts?

> > Also, I think there are quite some drivers already in the tree that don't
> > support suspend/resume explicitly and honestly we should start from adding the
> > suspend/resume routines to these drivers _before_ we ban new drivers like that.
> 
> It'd be relatively quick to modify all the current drivers that don't 
> explicitly support suspend/resume to explicitly not support it. (Or to 
> explicitly support it trivially; /dev/null obviously doesn't need 
> anything.)

The problem is we have to review quite a lot of drivers for this purpose.
Still it looks like we should do this anyway.

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: [PATCH] Re: NAK new drivers without proper power management?

[Willy Tarreau]

On Sat, Feb 10, 2007 at 08:50:27PM +0100, Rafael J. Wysocki wrote:
> On Saturday, 10 February 2007 18:52, Daniel Barkalow wrote:
> > On Sat, 10 Feb 2007, Rafael J. Wysocki wrote:
> > 
> > > On Saturday, 10 February 2007 11:02, Nigel Cunningham wrote:
> > >
> > > > Well, the original desire was to stop new drivers getting in without
> > > > proper power management.
> > > 
> > > I know, but I agree with the argument that having a driver without the
> > > suspend/resume support is better than not having the driver at all.
> > 
> > How about if "proper power management" is defined to include the driver 
> > explicitly preventing suspend? It seems to me like the current problem is 
> > that driver writers don't think about power management at all, and the 
> > result is that, after suspend/resume, the system doesn't come back. It 
> > would be better if driver writers had to think about power management just 
> > enough to realize that it's not going to work, and make this information 
> > available to the system. At that point, it's relatively easy for the 
> > system to do something useful about it.
> 
> Actually, it is easy for the driver authors to do this right now.  They can
> just make the .suspend() routine always return an error.
> 
> Well, I think this is a good idea: if the device in question requires specific
> power management during the suspend/resume, but it is not implemented by the
> driver, we should require the author of the driver to define the .suspend()
> routine that returns -ENOSYS (preferably, with an explanatory warning in
> dmesg).

instead of modifying all drivers to explicitly state that they don't support
it, we should start with a test of the NULL pointer for .suspend which should
mean exactly the same without modifying the drivers. I find it obvious that
a driver which does provide a suspend function will not support it. And if
some drivers (eg /dev/null) can support it anyway, it's better to change
*those* drivers to explicitly mark them as compatible.

regards,
Willy

Re: [PATCH] Re: NAK new drivers without proper power management?

[Willy Tarreau]

On Sat, Feb 10, 2007 at 08:50:27PM +0100, Rafael J. Wysocki wrote:
> On Saturday, 10 February 2007 18:52, Daniel Barkalow wrote:
> > On Sat, 10 Feb 2007, Rafael J. Wysocki wrote:
> > 
> > > On Saturday, 10 February 2007 11:02, Nigel Cunningham wrote:
> > >
> > > > Well, the original desire was to stop new drivers getting in without
> > > > proper power management.
> > > 
> > > I know, but I agree with the argument that having a driver without the
> > > suspend/resume support is better than not having the driver at all.
> > 
> > How about if "proper power management" is defined to include the driver 
> > explicitly preventing suspend? It seems to me like the current problem is 
> > that driver writers don't think about power management at all, and the 
> > result is that, after suspend/resume, the system doesn't come back. It 
> > would be better if driver writers had to think about power management just 
> > enough to realize that it's not going to work, and make this information 
> > available to the system. At that point, it's relatively easy for the 
> > system to do something useful about it.
> 
> Actually, it is easy for the driver authors to do this right now.  They can
> just make the .suspend() routine always return an error.
> 
> Well, I think this is a good idea: if the device in question requires specific
> power management during the suspend/resume, but it is not implemented by the
> driver, we should require the author of the driver to define the .suspend()
> routine that returns -ENOSYS (preferably, with an explanatory warning in
> dmesg).

instead of modifying all drivers to explicitly state that they don't support
it, we should start with a test of the NULL pointer for .suspend which should
mean exactly the same without modifying the drivers. I find it obvious that
a driver which does provide a suspend function will not support it. And if
some drivers (eg /dev/null) can support it anyway, it's better to change
*those* drivers to explicitly mark them as compatible.

regards,
Willy

Re: [PATCH] Re: NAK new drivers without proper power management?

[Matthew Garrett]

On Sun, Feb 11, 2007 at 07:54:04AM +0100, Willy Tarreau wrote:

> instead of modifying all drivers to explicitly state that they don't support
> it, we should start with a test of the NULL pointer for .suspend which should
> mean exactly the same without modifying the drivers. I find it obvious that
> a driver which does provide a suspend function will not support it. And if
> some drivers (eg /dev/null) can support it anyway, it's better to change
> *those* drivers to explicitly mark them as compatible.

No, that doesn't work. In the absence of suspend/resume methods, the PCI 
layer will implement basic PM itself. In some cases, this works. In 
others, it doesn't. There's no way to automatically determine which is 
which without modifying the drivers.

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

Re: [PATCH] Re: NAK new drivers without proper power management?

[Willy Tarreau]

On Sun, Feb 11, 2007 at 12:13:40PM +0000, Matthew Garrett wrote:
> On Sun, Feb 11, 2007 at 07:54:04AM +0100, Willy Tarreau wrote:
> 
> > instead of modifying all drivers to explicitly state that they don't support
> > it, we should start with a test of the NULL pointer for .suspend which should
> > mean exactly the same without modifying the drivers. I find it obvious that
> > a driver which does provide a suspend function will not support it. And if
> > some drivers (eg /dev/null) can support it anyway, it's better to change
> > *those* drivers to explicitly mark them as compatible.
> 
> No, that doesn't work. In the absence of suspend/resume methods, the PCI 
> layer will implement basic PM itself. In some cases, this works. In 
> others, it doesn't. There's no way to automatically determine which is 
> which without modifying the drivers.

Then change the PCI layer to do the basic PM only for known compatible
drivers, and modify only the known-compatible drivers to mark them
explicitly compatible. IMHO, it generally is a bad idea to require that
any driver explicitly states what it *does not* support. It's the reason
why users encounter problem on new features with old drivers. For instance,
do you know if the old ISA NE2000 driver breaks suspend ? I don't know,
but I would at least expect it not to support it by default. It's best
to announce what *is* supported and consider everything unimplemented
otherwise explicitly stated.

Regards,
Willy

Re: [PATCH] Re: NAK new drivers without proper power management?

[Willy Tarreau]

On Sun, Feb 11, 2007 at 12:13:40PM +0000, Matthew Garrett wrote:
> On Sun, Feb 11, 2007 at 07:54:04AM +0100, Willy Tarreau wrote:
> 
> > instead of modifying all drivers to explicitly state that they don't support
> > it, we should start with a test of the NULL pointer for .suspend which should
> > mean exactly the same without modifying the drivers. I find it obvious that
> > a driver which does provide a suspend function will not support it. And if
> > some drivers (eg /dev/null) can support it anyway, it's better to change
> > *those* drivers to explicitly mark them as compatible.
> 
> No, that doesn't work. In the absence of suspend/resume methods, the PCI 
> layer will implement basic PM itself. In some cases, this works. In 
> others, it doesn't. There's no way to automatically determine which is 
> which without modifying the drivers.

Then change the PCI layer to do the basic PM only for known compatible
drivers, and modify only the known-compatible drivers to mark them
explicitly compatible. IMHO, it generally is a bad idea to require that
any driver explicitly states what it *does not* support. It's the reason
why users encounter problem on new features with old drivers. For instance,
do you know if the old ISA NE2000 driver breaks suspend ? I don't know,
but I would at least expect it not to support it by default. It's best
to announce what *is* supported and consider everything unimplemented
otherwise explicitly stated.

Regards,
Willy

Re: [PATCH] Re: NAK new drivers without proper power management?

[Matthew Garrett]

On Sun, Feb 11, 2007 at 02:09:43PM +0100, Willy Tarreau wrote:

> Then change the PCI layer to do the basic PM only for known compatible
> drivers, and modify only the known-compatible drivers to mark them
> explicitly compatible. IMHO, it generally is a bad idea to require that
> any driver explicitly states what it *does not* support. It's the reason
> why users encounter problem on new features with old drivers. For instance,
> do you know if the old ISA NE2000 driver breaks suspend ? I don't know,
> but I would at least expect it not to support it by default. It's best
> to announce what *is* supported and consider everything unimplemented
> otherwise explicitly stated.

This ignores the reality of the situation, which is that many drivers 
support suspend and resume despite the lack of any explicit 
implementation. Changing things so they're flagged as broken when 
they're not would be a regression.

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

Re: [PATCH] Re: NAK new drivers without proper power management?

[Willy Tarreau]

On Sun, Feb 11, 2007 at 01:19:57PM +0000, Matthew Garrett wrote:
> On Sun, Feb 11, 2007 at 02:09:43PM +0100, Willy Tarreau wrote:
> 
> > Then change the PCI layer to do the basic PM only for known compatible
> > drivers, and modify only the known-compatible drivers to mark them
> > explicitly compatible. IMHO, it generally is a bad idea to require that
> > any driver explicitly states what it *does not* support. It's the reason
> > why users encounter problem on new features with old drivers. For instance,
> > do you know if the old ISA NE2000 driver breaks suspend ? I don't know,
> > but I would at least expect it not to support it by default. It's best
> > to announce what *is* supported and consider everything unimplemented
> > otherwise explicitly stated.
> 
> This ignores the reality of the situation, which is that many drivers 
> support suspend and resume despite the lack of any explicit 
> implementation. Changing things so they're flagged as broken when 
> they're not would be a regression.

Those which are identified as OK should be flagged OK. Only those for
which we have no idea should be flagged broken. It's better than leaving
them in the wild waiting for a victim. And given what Nigel would like,
they would all have to be reviewed to get .suspend/.resume entries
anyway. But at least, we would only have to change the known good instead
of all of them. And the remaining ones would not cause trouble to users.

Willy

Re: [PATCH] Re: NAK new drivers without proper power management?

[Willy Tarreau]

On Sun, Feb 11, 2007 at 01:19:57PM +0000, Matthew Garrett wrote:
> On Sun, Feb 11, 2007 at 02:09:43PM +0100, Willy Tarreau wrote:
> 
> > Then change the PCI layer to do the basic PM only for known compatible
> > drivers, and modify only the known-compatible drivers to mark them
> > explicitly compatible. IMHO, it generally is a bad idea to require that
> > any driver explicitly states what it *does not* support. It's the reason
> > why users encounter problem on new features with old drivers. For instance,
> > do you know if the old ISA NE2000 driver breaks suspend ? I don't know,
> > but I would at least expect it not to support it by default. It's best
> > to announce what *is* supported and consider everything unimplemented
> > otherwise explicitly stated.
> 
> This ignores the reality of the situation, which is that many drivers 
> support suspend and resume despite the lack of any explicit 
> implementation. Changing things so they're flagged as broken when 
> they're not would be a regression.

Those which are identified as OK should be flagged OK. Only those for
which we have no idea should be flagged broken. It's better than leaving
them in the wild waiting for a victim. And given what Nigel would like,
they would all have to be reviewed to get .suspend/.resume entries
anyway. But at least, we would only have to change the known good instead
of all of them. And the remaining ones would not cause trouble to users.

Willy

Re: [PATCH] Re: NAK new drivers without proper power management?

[Rafael J. Wysocki]

On Sunday, 11 February 2007 14:37, Willy Tarreau wrote:
> On Sun, Feb 11, 2007 at 01:19:57PM +0000, Matthew Garrett wrote:
> > On Sun, Feb 11, 2007 at 02:09:43PM +0100, Willy Tarreau wrote:
> > 
> > > Then change the PCI layer to do the basic PM only for known compatible
> > > drivers, and modify only the known-compatible drivers to mark them
> > > explicitly compatible. IMHO, it generally is a bad idea to require that
> > > any driver explicitly states what it *does not* support. It's the reason
> > > why users encounter problem on new features with old drivers. For instance,
> > > do you know if the old ISA NE2000 driver breaks suspend ? I don't know,
> > > but I would at least expect it not to support it by default. It's best
> > > to announce what *is* supported and consider everything unimplemented
> > > otherwise explicitly stated.
> > 
> > This ignores the reality of the situation, which is that many drivers 
> > support suspend and resume despite the lack of any explicit 
> > implementation. Changing things so they're flagged as broken when 
> > they're not would be a regression.
> 
> Those which are identified as OK should be flagged OK. Only those for
> which we have no idea should be flagged broken.

I think we don't need to flag the drivers identified as OK.  Let's flag only
the suspicious ones.

Whatever we finally come up with, I'd like to avoid modifying drivers that are
known good.

Greetings,
Rafael

Re: [PATCH] Re: NAK new drivers without proper power management?

[Rafael J. Wysocki]

On Sunday, 11 February 2007 14:37, Willy Tarreau wrote:
> On Sun, Feb 11, 2007 at 01:19:57PM +0000, Matthew Garrett wrote:
> > On Sun, Feb 11, 2007 at 02:09:43PM +0100, Willy Tarreau wrote:
> > 
> > > Then change the PCI layer to do the basic PM only for known compatible
> > > drivers, and modify only the known-compatible drivers to mark them
> > > explicitly compatible. IMHO, it generally is a bad idea to require that
> > > any driver explicitly states what it *does not* support. It's the reason
> > > why users encounter problem on new features with old drivers. For instance,
> > > do you know if the old ISA NE2000 driver breaks suspend ? I don't know,
> > > but I would at least expect it not to support it by default. It's best
> > > to announce what *is* supported and consider everything unimplemented
> > > otherwise explicitly stated.
> > 
> > This ignores the reality of the situation, which is that many drivers 
> > support suspend and resume despite the lack of any explicit 
> > implementation. Changing things so they're flagged as broken when 
> > they're not would be a regression.
> 
> Those which are identified as OK should be flagged OK. Only those for
> which we have no idea should be flagged broken.

I think we don't need to flag the drivers identified as OK.  Let's flag only
the suspicious ones.

Whatever we finally come up with, I'd like to avoid modifying drivers that are
known good.

Greetings,
Rafael

Re: [PATCH] Re: NAK new drivers without proper power management?

[Willy Tarreau]

On Sun, Feb 11, 2007 at 02:50:48PM +0100, Rafael J. Wysocki wrote:
> On Sunday, 11 February 2007 14:37, Willy Tarreau wrote:
> > On Sun, Feb 11, 2007 at 01:19:57PM +0000, Matthew Garrett wrote:
> > > On Sun, Feb 11, 2007 at 02:09:43PM +0100, Willy Tarreau wrote:
> > > 
> > > > Then change the PCI layer to do the basic PM only for known compatible
> > > > drivers, and modify only the known-compatible drivers to mark them
> > > > explicitly compatible. IMHO, it generally is a bad idea to require that
> > > > any driver explicitly states what it *does not* support. It's the reason
> > > > why users encounter problem on new features with old drivers. For instance,
> > > > do you know if the old ISA NE2000 driver breaks suspend ? I don't know,
> > > > but I would at least expect it not to support it by default. It's best
> > > > to announce what *is* supported and consider everything unimplemented
> > > > otherwise explicitly stated.
> > > 
> > > This ignores the reality of the situation, which is that many drivers 
> > > support suspend and resume despite the lack of any explicit 
> > > implementation. Changing things so they're flagged as broken when 
> > > they're not would be a regression.
> > 
> > Those which are identified as OK should be flagged OK. Only those for
> > which we have no idea should be flagged broken.
> 
> I think we don't need to flag the drivers identified as OK.  Let's flag only
> the suspicious ones.
> 
> Whatever we finally come up with, I'd like to avoid modifying drivers that are
> known good.

I understand your concerns, but the problem is not *current* drivers, but
what will happen to *new* drivers. If we make it implicit that a driver
is compatible, then new drivers will be promoted as good even if nothing
has been done for this.

Regards,
Willy

Re: [PATCH] Re: NAK new drivers without proper power management?

[Willy Tarreau]

On Sun, Feb 11, 2007 at 02:50:48PM +0100, Rafael J. Wysocki wrote:
> On Sunday, 11 February 2007 14:37, Willy Tarreau wrote:
> > On Sun, Feb 11, 2007 at 01:19:57PM +0000, Matthew Garrett wrote:
> > > On Sun, Feb 11, 2007 at 02:09:43PM +0100, Willy Tarreau wrote:
> > > 
> > > > Then change the PCI layer to do the basic PM only for known compatible
> > > > drivers, and modify only the known-compatible drivers to mark them
> > > > explicitly compatible. IMHO, it generally is a bad idea to require that
> > > > any driver explicitly states what it *does not* support. It's the reason
> > > > why users encounter problem on new features with old drivers. For instance,
> > > > do you know if the old ISA NE2000 driver breaks suspend ? I don't know,
> > > > but I would at least expect it not to support it by default. It's best
> > > > to announce what *is* supported and consider everything unimplemented
> > > > otherwise explicitly stated.
> > > 
> > > This ignores the reality of the situation, which is that many drivers 
> > > support suspend and resume despite the lack of any explicit 
> > > implementation. Changing things so they're flagged as broken when 
> > > they're not would be a regression.
> > 
> > Those which are identified as OK should be flagged OK. Only those for
> > which we have no idea should be flagged broken.
> 
> I think we don't need to flag the drivers identified as OK.  Let's flag only
> the suspicious ones.
> 
> Whatever we finally come up with, I'd like to avoid modifying drivers that are
> known good.

I understand your concerns, but the problem is not *current* drivers, but
what will happen to *new* drivers. If we make it implicit that a driver
is compatible, then new drivers will be promoted as good even if nothing
has been done for this.

Regards,
Willy

Re: [PATCH] Re: NAK new drivers without proper power management?

[Rafael J. Wysocki]

On Sunday, 11 February 2007 14:57, Willy Tarreau wrote:
> On Sun, Feb 11, 2007 at 02:50:48PM +0100, Rafael J. Wysocki wrote:
> > On Sunday, 11 February 2007 14:37, Willy Tarreau wrote:
> > > On Sun, Feb 11, 2007 at 01:19:57PM +0000, Matthew Garrett wrote:
> > > > On Sun, Feb 11, 2007 at 02:09:43PM +0100, Willy Tarreau wrote:
> > > > 
> > > > > Then change the PCI layer to do the basic PM only for known compatible
> > > > > drivers, and modify only the known-compatible drivers to mark them
> > > > > explicitly compatible. IMHO, it generally is a bad idea to require that
> > > > > any driver explicitly states what it *does not* support. It's the reason
> > > > > why users encounter problem on new features with old drivers. For instance,
> > > > > do you know if the old ISA NE2000 driver breaks suspend ? I don't know,
> > > > > but I would at least expect it not to support it by default. It's best
> > > > > to announce what *is* supported and consider everything unimplemented
> > > > > otherwise explicitly stated.
> > > > 
> > > > This ignores the reality of the situation, which is that many drivers 
> > > > support suspend and resume despite the lack of any explicit 
> > > > implementation. Changing things so they're flagged as broken when 
> > > > they're not would be a regression.
> > > 
> > > Those which are identified as OK should be flagged OK. Only those for
> > > which we have no idea should be flagged broken.
> > 
> > I think we don't need to flag the drivers identified as OK.  Let's flag only
> > the suspicious ones.
> > 
> > Whatever we finally come up with, I'd like to avoid modifying drivers that are
> > known good.
> 
> I understand your concerns, but the problem is not *current* drivers, but
> what will happen to *new* drivers. If we make it implicit that a driver
> is compatible, then new drivers will be promoted as good even if nothing
> has been done for this.

The problem is it was made implicit long ago.  The design is "optimistic", so
to speak, and I think we have the following choices:

1) Change the design to make the kernel refuse to suspend if there are any
drivers not explicitly flagged as "suspend/resume-safe".  [This looks like a
lot of work to me, but it is generally doable provided that someone has enough
time to do it.  Unfortunately it has to be done in one shot for all of the
known good drivers to avoid user-observable regressions.]

2) Require the authors of new drivers to _either_ ensure that their drivers
will be suspend/resume-safe (and I mean both STR and STD here), _or_ explicitly
flag the drivers as "suspend/resume-unsafe", for example by impelenting
.suspend() routines returning -ENOSYS.  [The existing drivers can be modified
to follow this convention gradually.]

Now IMO 1) has some disadvantages:
- Potential for introducing some regressions (eg. if we omit a known-good
driver)
- Necessity to review a lot of drivers simultaneously
- Problem what to do with drivers that work for some people and don't work
for the others (ie. if we don't flag them as known good, we will break the
setups in which they work)

The advantage of 1), however, is that we can differentiate drivers that are
safe only with respect to the suspend to disk from those that are safe with
respect to the suspend to RAM too (there are some).

I'd prefer 2), because it's simpler to make happen.

Greetings,
Rafael

Re: [PATCH] Re: NAK new drivers without proper power management?

[Rafael J. Wysocki]

On Sunday, 11 February 2007 14:57, Willy Tarreau wrote:
> On Sun, Feb 11, 2007 at 02:50:48PM +0100, Rafael J. Wysocki wrote:
> > On Sunday, 11 February 2007 14:37, Willy Tarreau wrote:
> > > On Sun, Feb 11, 2007 at 01:19:57PM +0000, Matthew Garrett wrote:
> > > > On Sun, Feb 11, 2007 at 02:09:43PM +0100, Willy Tarreau wrote:
> > > > 
> > > > > Then change the PCI layer to do the basic PM only for known compatible
> > > > > drivers, and modify only the known-compatible drivers to mark them
> > > > > explicitly compatible. IMHO, it generally is a bad idea to require that
> > > > > any driver explicitly states what it *does not* support. It's the reason
> > > > > why users encounter problem on new features with old drivers. For instance,
> > > > > do you know if the old ISA NE2000 driver breaks suspend ? I don't know,
> > > > > but I would at least expect it not to support it by default. It's best
> > > > > to announce what *is* supported and consider everything unimplemented
> > > > > otherwise explicitly stated.
> > > > 
> > > > This ignores the reality of the situation, which is that many drivers 
> > > > support suspend and resume despite the lack of any explicit 
> > > > implementation. Changing things so they're flagged as broken when 
> > > > they're not would be a regression.
> > > 
> > > Those which are identified as OK should be flagged OK. Only those for
> > > which we have no idea should be flagged broken.
> > 
> > I think we don't need to flag the drivers identified as OK.  Let's flag only
> > the suspicious ones.
> > 
> > Whatever we finally come up with, I'd like to avoid modifying drivers that are
> > known good.
> 
> I understand your concerns, but the problem is not *current* drivers, but
> what will happen to *new* drivers. If we make it implicit that a driver
> is compatible, then new drivers will be promoted as good even if nothing
> has been done for this.

The problem is it was made implicit long ago.  The design is "optimistic", so
to speak, and I think we have the following choices:

1) Change the design to make the kernel refuse to suspend if there are any
drivers not explicitly flagged as "suspend/resume-safe".  [This looks like a
lot of work to me, but it is generally doable provided that someone has enough
time to do it.  Unfortunately it has to be done in one shot for all of the
known good drivers to avoid user-observable regressions.]

2) Require the authors of new drivers to _either_ ensure that their drivers
will be suspend/resume-safe (and I mean both STR and STD here), _or_ explicitly
flag the drivers as "suspend/resume-unsafe", for example by impelenting
.suspend() routines returning -ENOSYS.  [The existing drivers can be modified
to follow this convention gradually.]

Now IMO 1) has some disadvantages:
- Potential for introducing some regressions (eg. if we omit a known-good
driver)
- Necessity to review a lot of drivers simultaneously
- Problem what to do with drivers that work for some people and don't work
for the others (ie. if we don't flag them as known good, we will break the
setups in which they work)

The advantage of 1), however, is that we can differentiate drivers that are
safe only with respect to the suspend to disk from those that are safe with
respect to the suspend to RAM too (there are some).

I'd prefer 2), because it's simpler to make happen.

Greetings,
Rafael

Re: [PATCH] Re: NAK new drivers without proper power management?

[Pekka Enberg]

On 2/11/07, Rafael J. Wysocki <rjw@sisk.pl> wrote:
> Unfortunately it has to be done in one shot for all of the known good drivers to avoid
> user-observable regressions.

No you don't. You can make it a config option that defaults to n
during a transition period.

Re: [PATCH] Re: NAK new drivers without proper power management?

[Pekka Enberg]

On 2/11/07, Rafael J. Wysocki <rjw@sisk.pl> wrote:
> Unfortunately it has to be done in one shot for all of the known good drivers to avoid
> user-observable regressions.

No you don't. You can make it a config option that defaults to n
during a transition period.

Re: [PATCH] Re: NAK new drivers without proper power management?

[Rafael J. Wysocki]

On Sunday, 11 February 2007 16:19, Pekka Enberg wrote:
> On 2/11/07, Rafael J. Wysocki <rjw@sisk.pl> wrote:
> > Unfortunately it has to be done in one shot for all of the known good drivers to avoid
> > user-observable regressions.
> 
> No you don't. You can make it a config option that defaults to n
> during a transition period.

Yes, that's possible.

Greetings,
Rafael

Re: [PATCH] Re: NAK new drivers without proper power management?

[Rafael J. Wysocki]

On Sunday, 11 February 2007 16:19, Pekka Enberg wrote:
> On 2/11/07, Rafael J. Wysocki <rjw@sisk.pl> wrote:
> > Unfortunately it has to be done in one shot for all of the known good drivers to avoid
> > user-observable regressions.
> 
> No you don't. You can make it a config option that defaults to n
> during a transition period.

Yes, that's possible.

Greetings,
Rafael

Re: [PATCH] Re: NAK new drivers without proper power management?

[Daniel Barkalow]

On Sun, 11 Feb 2007, Rafael J. Wysocki wrote:

> The problem is it was made implicit long ago.  The design is "optimistic", so
> to speak, and I think we have the following choices:
> 
> 1) Change the design to make the kernel refuse to suspend if there are any
> drivers not explicitly flagged as "suspend/resume-safe".  [This looks like a
> lot of work to me, but it is generally doable provided that someone has enough
> time to do it.  Unfortunately it has to be done in one shot for all of the
> known good drivers to avoid user-observable regressions.]

The kernel wouldn't necessarily have to refuse to suspend. It could just 
warn (and list the drivers that aren't marked), or could require some 
extra insistance from the user. It would be good to have it log a message 
saying something like: "If you can read this, report that ne2000 seems to 
be safe for suspend/resume". Having drivers explicitly marked as to 
whether they are safe is a good kernel feature; what to do if they're not 
is policy.

> 2) Require the authors of new drivers to _either_ ensure that their drivers
> will be suspend/resume-safe (and I mean both STR and STD here), _or_ explicitly
> flag the drivers as "suspend/resume-unsafe", for example by impelenting
> .suspend() routines returning -ENOSYS.  [The existing drivers can be modified
> to follow this convention gradually.]

I don't see any reason not to do (2) regardless of (1). That was (my idea 
of) the statement that started this thread: new drivers need to not mess 
up on suspend/resume, as a matter of suitability for inclusion. Of course, 
we need some way for drivers to indicate that they work fine with the 
PCI-layer defaults. And it should probably more machine-readable than the 
author telling reviewers that it works.

> - Problem what to do with drivers that work for some people and don't work
> for the others (ie. if we don't flag them as known good, we will break the
> setups in which they work)

I think the only interesting case here is when a device resumes fine with 
no driver support if the BIOS manages to deal effectively with it, but the 
BIOS generally doesn't. Otherwise, I think it's only going to work at 
all if the author put in the effort to make it work (so it should be 
"known good"), but there may be bugs (firmware, BIOS, driver, etc). But 
that's true of any functionality.

	-Daniel
*This .sig left intentionally blank*

Re: [PATCH] Re: NAK new drivers without proper power management?

[Rafael J. Wysocki]

On Sunday, 11 February 2007 18:27, Daniel Barkalow wrote:
> On Sun, 11 Feb 2007, Rafael J. Wysocki wrote:
> 
> > The problem is it was made implicit long ago.  The design is "optimistic", so
> > to speak, and I think we have the following choices:
> > 
> > 1) Change the design to make the kernel refuse to suspend if there are any
> > drivers not explicitly flagged as "suspend/resume-safe".  [This looks like a
> > lot of work to me, but it is generally doable provided that someone has enough
> > time to do it.  Unfortunately it has to be done in one shot for all of the
> > known good drivers to avoid user-observable regressions.]
> 
> The kernel wouldn't necessarily have to refuse to suspend.

Well, not from the start, but I think at some point in the fufure it would.

> It could just warn (and list the drivers that aren't marked), or could
> require some extra insistance from the user.

We would have to change the interface for that and I don't want to do it.

> It would be good to have it log a message saying something like: "If you can
> read this, report that ne2000 seems to be safe for suspend/resume".

Sure, it would.

> Having drivers explicitly marked as to whether they are safe is a good kernel
> feature; what to do if they're not is policy.

That's true, but I assume that the people who opt for doing that are also
willing to take part in the review of the drivers. :-)

> > 2) Require the authors of new drivers to _either_ ensure that their drivers
> > will be suspend/resume-safe (and I mean both STR and STD here), _or_ explicitly
> > flag the drivers as "suspend/resume-unsafe", for example by impelenting
> > .suspend() routines returning -ENOSYS.  [The existing drivers can be modified
> > to follow this convention gradually.]
> 
> I don't see any reason not to do (2) regardless of (1). That was (my idea 
> of) the statement that started this thread: new drivers need to not mess 
> up on suspend/resume, as a matter of suitability for inclusion. Of course, 
> we need some way for drivers to indicate that they work fine with the 
> PCI-layer defaults. And it should probably more machine-readable than the 
> author telling reviewers that it works.

Well, if we change the design to fail by default, the authors of new drivers
will only have to flag them if they believe that the drivers are
suspend/resume-safe.

> > - Problem what to do with drivers that work for some people and don't work
> > for the others (ie. if we don't flag them as known good, we will break the
> > setups in which they work)
> 
> I think the only interesting case here is when a device resumes fine with 
> no driver support if the BIOS manages to deal effectively with it, but the 
> BIOS generally doesn't.

Well, I don't think so.  Let's estimate the number of drivers that define
.resume() right now:

$ grep -I -l -r '.resume =' linux-2.6.20/drivers/ | wc
    102     102    4169

And I think there are much more drivers that really work fine with respect
to the suspend/resume.

This indicates that in fact many drivers can be marked as known good even
though they don't define the .suspend() or .resume() routines.

Greetings,
Rafael

Re: [PATCH] Re: NAK new drivers without proper power management?

[Rafael J. Wysocki]

On Sunday, 11 February 2007 18:27, Daniel Barkalow wrote:
> On Sun, 11 Feb 2007, Rafael J. Wysocki wrote:
> 
> > The problem is it was made implicit long ago.  The design is "optimistic", so
> > to speak, and I think we have the following choices:
> > 
> > 1) Change the design to make the kernel refuse to suspend if there are any
> > drivers not explicitly flagged as "suspend/resume-safe".  [This looks like a
> > lot of work to me, but it is generally doable provided that someone has enough
> > time to do it.  Unfortunately it has to be done in one shot for all of the
> > known good drivers to avoid user-observable regressions.]
> 
> The kernel wouldn't necessarily have to refuse to suspend.

Well, not from the start, but I think at some point in the fufure it would.

> It could just warn (and list the drivers that aren't marked), or could
> require some extra insistance from the user.

We would have to change the interface for that and I don't want to do it.

> It would be good to have it log a message saying something like: "If you can
> read this, report that ne2000 seems to be safe for suspend/resume".

Sure, it would.

> Having drivers explicitly marked as to whether they are safe is a good kernel
> feature; what to do if they're not is policy.

That's true, but I assume that the people who opt for doing that are also
willing to take part in the review of the drivers. :-)

> > 2) Require the authors of new drivers to _either_ ensure that their drivers
> > will be suspend/resume-safe (and I mean both STR and STD here), _or_ explicitly
> > flag the drivers as "suspend/resume-unsafe", for example by impelenting
> > .suspend() routines returning -ENOSYS.  [The existing drivers can be modified
> > to follow this convention gradually.]
> 
> I don't see any reason not to do (2) regardless of (1). That was (my idea 
> of) the statement that started this thread: new drivers need to not mess 
> up on suspend/resume, as a matter of suitability for inclusion. Of course, 
> we need some way for drivers to indicate that they work fine with the 
> PCI-layer defaults. And it should probably more machine-readable than the 
> author telling reviewers that it works.

Well, if we change the design to fail by default, the authors of new drivers
will only have to flag them if they believe that the drivers are
suspend/resume-safe.

> > - Problem what to do with drivers that work for some people and don't work
> > for the others (ie. if we don't flag them as known good, we will break the
> > setups in which they work)
> 
> I think the only interesting case here is when a device resumes fine with 
> no driver support if the BIOS manages to deal effectively with it, but the 
> BIOS generally doesn't.

Well, I don't think so.  Let's estimate the number of drivers that define
.resume() right now:

$ grep -I -l -r '.resume =' linux-2.6.20/drivers/ | wc
    102     102    4169

And I think there are much more drivers that really work fine with respect
to the suspend/resume.

This indicates that in fact many drivers can be marked as known good even
though they don't define the .suspend() or .resume() routines.

Greetings,
Rafael

Re: [PATCH] Re: NAK new drivers without proper power management?

[Nigel Cunningham]

Hi.

On Sun, 2007-02-11 at 19:53 +0100, Rafael J. Wysocki wrote:
> > Having drivers explicitly marked as to whether they are safe is a good kernel
> > feature; what to do if they're not is policy.
> 
> That's true, but I assume that the people who opt for doing that are also
> willing to take part in the review of the drivers. :-)

Absolutely :)

> Well, I don't think so.  Let's estimate the number of drivers that define
> .resume() right now:
> 
> $ grep -I -l -r '.resume =' linux-2.6.20/drivers/ | wc
>     102     102    4169

I think the '.resume =' doesn't help - some have tabs. I ran '\.resume'
and got 351.

It would be interesting to see how many struct pci_driver etc instances
lack resume methods.

Regards,

Nige

Re: [PATCH] Re: NAK new drivers without proper power management?

[Nigel Cunningham]

Hi.

On Sun, 2007-02-11 at 19:53 +0100, Rafael J. Wysocki wrote:
> > Having drivers explicitly marked as to whether they are safe is a good kernel
> > feature; what to do if they're not is policy.
> 
> That's true, but I assume that the people who opt for doing that are also
> willing to take part in the review of the drivers. :-)

Absolutely :)

> Well, I don't think so.  Let's estimate the number of drivers that define
> .resume() right now:
> 
> $ grep -I -l -r '.resume =' linux-2.6.20/drivers/ | wc
>     102     102    4169

I think the '.resume =' doesn't help - some have tabs. I ran '\.resume'
and got 351.

It would be interesting to see how many struct pci_driver etc instances
lack resume methods.

Regards,

Nige

Re: [PATCH] Re: NAK new drivers without proper power management?

[Rafael J. Wysocki]

On Monday, 12 February 2007 00:06, Nigel Cunningham wrote:
> Hi.
> 
> On Sun, 2007-02-11 at 19:53 +0100, Rafael J. Wysocki wrote:
> > > Having drivers explicitly marked as to whether they are safe is a good kernel
> > > feature; what to do if they're not is policy.
> > 
> > That's true, but I assume that the people who opt for doing that are also
> > willing to take part in the review of the drivers. :-)
> 
> Absolutely :)
> 
> > Well, I don't think so.  Let's estimate the number of drivers that define
> > .resume() right now:
> > 
> > $ grep -I -l -r '.resume =' linux-2.6.20/drivers/ | wc
> >     102     102    4169
> 
> I think the '.resume =' doesn't help - some have tabs. I ran '\.resume'
> and got 351.

Ah, good catch.  I have searched for ".resume" only and got 612, but this
is the number of files, not the number of drivers.  And it is not exactly
large. ;-)

> It would be interesting to see how many struct pci_driver etc instances
> lack resume methods.

Yes, I'll try to invent a test.

Greetings,
Rafael

Re: [PATCH] Re: NAK new drivers without proper power management?

[Rafael J. Wysocki]

On Monday, 12 February 2007 00:06, Nigel Cunningham wrote:
> Hi.
> 
> On Sun, 2007-02-11 at 19:53 +0100, Rafael J. Wysocki wrote:
> > > Having drivers explicitly marked as to whether they are safe is a good kernel
> > > feature; what to do if they're not is policy.
> > 
> > That's true, but I assume that the people who opt for doing that are also
> > willing to take part in the review of the drivers. :-)
> 
> Absolutely :)
> 
> > Well, I don't think so.  Let's estimate the number of drivers that define
> > .resume() right now:
> > 
> > $ grep -I -l -r '.resume =' linux-2.6.20/drivers/ | wc
> >     102     102    4169
> 
> I think the '.resume =' doesn't help - some have tabs. I ran '\.resume'
> and got 351.

Ah, good catch.  I have searched for ".resume" only and got 612, but this
is the number of files, not the number of drivers.  And it is not exactly
large. ;-)

> It would be interesting to see how many struct pci_driver etc instances
> lack resume methods.

Yes, I'll try to invent a test.

Greetings,
Rafael

Re: [PATCH] Re: NAK new drivers without proper power management?

[Stefan Richter]

Rafael J. Wysocki wrote:
> - Problem what to do with drivers that work for some people and don't work
> for the others (ie. if we don't flag them as known good, we will break the
> setups in which they work)

And this issue is independent of whether a driver has .suspend and
.resume or not. For example, ohci1394 had them for ages but they didn't
work as expected before 2.6.20.

What's more, ohci1394's resume routine alone is insufficient; an
additional facility in ieee1394 was necessary and added for 2.6.21(-rc).
This shows that the original authors of ohci1394's .suspend and .resume
didn't test with actual external devices or gave up when they figured
that the problem reaches into upper subsystem layers. (We still haven't
tested interaction with most of the IEEE 1394 high level.)
-- 
Stefan Richter
-=====-=-=== --=- -=-==
http://arcgraph.de/sr/

Re: [PATCH] Re: NAK new drivers without proper power management?

[Stefan Richter]

Rafael J. Wysocki wrote:
> - Problem what to do with drivers that work for some people and don't work
> for the others (ie. if we don't flag them as known good, we will break the
> setups in which they work)

And this issue is independent of whether a driver has .suspend and
.resume or not. For example, ohci1394 had them for ages but they didn't
work as expected before 2.6.20.

What's more, ohci1394's resume routine alone is insufficient; an
additional facility in ieee1394 was necessary and added for 2.6.21(-rc).
This shows that the original authors of ohci1394's .suspend and .resume
didn't test with actual external devices or gave up when they figured
that the problem reaches into upper subsystem layers. (We still haven't
tested interaction with most of the IEEE 1394 high level.)
-- 
Stefan Richter
-=====-=-=== --=- -=-==
http://arcgraph.de/sr/

Re: [PATCH] Re: NAK new drivers without proper power management?

[Pavel Machek]

Hi!

> > > instead of modifying all drivers to explicitly state that they don't support
> > > it, we should start with a test of the NULL pointer for .suspend which should
> > > mean exactly the same without modifying the drivers. I find it obvious that
> > > a driver which does provide a suspend function will not support it. And if
> > > some drivers (eg /dev/null) can support it anyway, it's better to change
> > > *those* drivers to explicitly mark them as compatible.
> > 
> > No, that doesn't work. In the absence of suspend/resume methods, the PCI 
> > layer will implement basic PM itself. In some cases, this works. In 
> > others, it doesn't. There's no way to automatically determine which is 
> > which without modifying the drivers.
> 
> Then change the PCI layer to do the basic PM only for known compatible
> drivers, and modify only the known-compatible drivers to mark them
> explicitly compatible. IMHO, it generally is a bad idea to require that
> any driver explicitly states what it *does not* support. It's the reason
> why users encounter problem on new features with old drivers. For instance,
> do you know if the old ISA NE2000 driver breaks suspend ? I don't know,
> but I would at least expect it not to support it by default. It's best
> to announce what *is* supported and consider everything unimplemented
> otherwise explicitly stated.

Actually, ne2k driver is okay. ne2k cards are notoriously buggy, so it
responds with "****, that damn card has just locked up again, lets
reset it". Ok, it takes timeout to realize card is "locked up",
so it could be improved...

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

Re: [PATCH] Re: NAK new drivers without proper power management?

[Robert Hancock]

Matthew Garrett wrote:
> On Sun, Feb 11, 2007 at 07:54:04AM +0100, Willy Tarreau wrote:
> 
>> instead of modifying all drivers to explicitly state that they don't support
>> it, we should start with a test of the NULL pointer for .suspend which should
>> mean exactly the same without modifying the drivers. I find it obvious that
>> a driver which does provide a suspend function will not support it. And if
>> some drivers (eg /dev/null) can support it anyway, it's better to change
>> *those* drivers to explicitly mark them as compatible.
> 
> No, that doesn't work. In the absence of suspend/resume methods, the PCI 
> layer will implement basic PM itself. In some cases, this works. In 
> others, it doesn't. There's no way to automatically determine which is 
> which without modifying the drivers.
> 

The only thing that the PCI layer does for PM is the stuff that the 
driver would normally tell the PCI layer to do as part of a proper 
suspend/resume implementation: enable/disable the device and 
save/restore the PCI configuration space (only the standardized part, I 
believe). This is the bare minimum that's needed on all PCI devices, 
whether or not they even have a driver loaded. I suspect the number of 
PCI devices where this is truly all they need, i.e. no state in any IO 
ports or MMIO registers that need to be reset on resume, is quite low. 
Maybe in some cases it may appear to work by luck, i.e. the registers 
happening to be set to the correct values (especially on 
suspend-to-disk) but this is not a proper implementation.

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

Re: [PATCH] Re: NAK new drivers without proper power management?

[Nigel Cunningham]

Hi.

On Sun, 2007-02-11 at 12:13 +0000, Matthew Garrett wrote:
> On Sun, Feb 11, 2007 at 07:54:04AM +0100, Willy Tarreau wrote:
> 
> > instead of modifying all drivers to explicitly state that they don't support
> > it, we should start with a test of the NULL pointer for .suspend which should
> > mean exactly the same without modifying the drivers. I find it obvious that
> > a driver which does provide a suspend function will not support it. And if
> > some drivers (eg /dev/null) can support it anyway, it's better to change
> > *those* drivers to explicitly mark them as compatible.
> 
> No, that doesn't work. In the absence of suspend/resume methods, the PCI 
> layer will implement basic PM itself. In some cases, this works. In 
> others, it doesn't. There's no way to automatically determine which is 
> which without modifying the drivers.

I think we have it backwards there. Power management support for a
driver should always start with the driver itself. If there's a generic
routine that can be used for the bus, the driver should explicitly set
the routine to the generic routine.

Regards,

Nigel

Re: [PATCH] Re: NAK new drivers without proper power management?

[Pavel Machek]

Hi!

> > Also, I think there are quite some drivers already in the tree that don't
> > support suspend/resume explicitly and honestly we should start from adding the
> > suspend/resume routines to these drivers _before_ we ban new drivers like that.
> 
> It'd be relatively quick to modify all the current drivers that don't 
> explicitly support suspend/resume to explicitly not support it. (Or

Well, I think that is more work than you realize, but yes, that patch
would really be welcome.
								Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

Re: [PATCH] Re: NAK new drivers without proper power management?

[Pavel Machek]

Hi!

> > Also, I think there are quite some drivers already in the tree that don't
> > support suspend/resume explicitly and honestly we should start from adding the
> > suspend/resume routines to these drivers _before_ we ban new drivers like that.
> 
> It'd be relatively quick to modify all the current drivers that don't 
> explicitly support suspend/resume to explicitly not support it. (Or

Well, I think that is more work than you realize, but yes, that patch
would really 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?

[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/