[PATCH] serdev: Don't claim unsupported serial devices

[PATCH] serdev: Don't claim unsupported serial devices

[Punit Agrawal]

Serdev sub-system claims all serial devices that are not already
enumerated. As a result, no device node is created for serial port on
certain boards such as the Apollo Lake based UP2. This has the
unintended consequence of not being able to raise the login prompt via
serial connection.

Introduce a blacklist to reject devices that should not be treated as
a serdev device. Add the Intel HS UART peripheral ids to the blacklist
to bring back serial port on SoCs carrying them.

Cc: stable@vger.kernel.org
Signed-off-by: Punit Agrawal <punit1.agrawal@toshiba.co.jp>
Cc: Rob Herring <robh@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Johan Hovold <johan@kernel.org>
Cc: Hans de Goede <hdegoede@redhat.com>
---

Hi,

The patch has been updated based on feedback recieved on the RFC[0].

Please consider merging if there are no objections.

Thanks,
Punit

[0] https://www.spinics.net/lists/linux-serial/msg36646.html

 drivers/tty/serdev/core.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/tty/serdev/core.c b/drivers/tty/serdev/core.c
index 226adeec2aed..0d64fb7d4f36 100644
--- a/drivers/tty/serdev/core.c
+++ b/drivers/tty/serdev/core.c
@@ -663,6 +663,12 @@ static acpi_status acpi_serdev_register_device(struct serdev_controller *ctrl,
 	return AE_OK;
 }
 
+static const struct acpi_device_id serdev_blacklist_devices[] = {
+	{"INT3511", 0},
+	{"INT3512", 0},
+	{ },
+};
+
 static acpi_status acpi_serdev_add_device(acpi_handle handle, u32 level,
 					  void *data, void **return_value)
 {
@@ -675,6 +681,10 @@ static acpi_status acpi_serdev_add_device(acpi_handle handle, u32 level,
 	if (acpi_device_enumerated(adev))
 		return AE_OK;
 
+	/* Skip if black listed */
+	if (!acpi_match_device_ids(adev, serdev_blacklist_devices))
+		return AE_OK;
+
 	if (acpi_serdev_check_resources(ctrl, adev))
 		return AE_OK;
 
-- 
2.24.0

Re: [PATCH] serdev: Don't claim unsupported serial devices

[Greg Kroah-Hartman]

On Wed, Dec 18, 2019 at 03:56:46PM +0900, Punit Agrawal wrote:
> Serdev sub-system claims all serial devices that are not already
> enumerated.

All ACPI serial devices, right?  Surely not all other types of serial
devices in the system.

And what do you mean by "not already enumerated"?

> As a result, no device node is created for serial port on
> certain boards such as the Apollo Lake based UP2. This has the
> unintended consequence of not being able to raise the login prompt via
> serial connection.
> 
> Introduce a blacklist to reject devices that should not be treated as

"reject ACPI serial devices"

> a serdev device. Add the Intel HS UART peripheral ids to the blacklist
> to bring back serial port on SoCs carrying them.
> 
> Cc: stable@vger.kernel.org
> Signed-off-by: Punit Agrawal <punit1.agrawal@toshiba.co.jp>
> Cc: Rob Herring <robh@kernel.org>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Johan Hovold <johan@kernel.org>
> Cc: Hans de Goede <hdegoede@redhat.com>
> ---
> 
> Hi,
> 
> The patch has been updated based on feedback recieved on the RFC[0].
> 
> Please consider merging if there are no objections.
> 
> Thanks,
> Punit
> 
> [0] https://www.spinics.net/lists/linux-serial/msg36646.html
> 
>  drivers/tty/serdev/core.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/drivers/tty/serdev/core.c b/drivers/tty/serdev/core.c
> index 226adeec2aed..0d64fb7d4f36 100644
> --- a/drivers/tty/serdev/core.c
> +++ b/drivers/tty/serdev/core.c
> @@ -663,6 +663,12 @@ static acpi_status acpi_serdev_register_device(struct serdev_controller *ctrl,
>  	return AE_OK;
>  }
>  
> +static const struct acpi_device_id serdev_blacklist_devices[] = {

s/serdev_blacklist_devices/serdev_blacklist/acpi_devices/  ?

This is an acpi-specific thing, not a generic tty thing.

thanks,

greg k-h

Re: [PATCH] serdev: Don't claim unsupported serial devices

[Punit Agrawal]

Hi Greg,

Greg Kroah-Hartman <gregkh@linuxfoundation.org> writes:

> On Wed, Dec 18, 2019 at 03:56:46PM +0900, Punit Agrawal wrote:
>> Serdev sub-system claims all serial devices that are not already
>> enumerated.
>
> All ACPI serial devices, right?  Surely not all other types of serial
> devices in the system.

That's right - I'll tighten the wording in the commit log and the patch
below to be ACPI specific.

>
> And what do you mean by "not already enumerated"?

This is referring to check using "acpi_device_enumerated()" when walking
ACPI devices. But the intention was to convey uninitialised serial
devices exposed via ACPI.

I'll update this as well.

Thanks for the review.

Punit

>
>> As a result, no device node is created for serial port on
>> certain boards such as the Apollo Lake based UP2. This has the
>> unintended consequence of not being able to raise the login prompt via
>> serial connection.
>> 
>> Introduce a blacklist to reject devices that should not be treated as
>
> "reject ACPI serial devices"
>
>> a serdev device. Add the Intel HS UART peripheral ids to the blacklist
>> to bring back serial port on SoCs carrying them.
>> 
>> Cc: stable@vger.kernel.org
>> Signed-off-by: Punit Agrawal <punit1.agrawal@toshiba.co.jp>
>> Cc: Rob Herring <robh@kernel.org>
>> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>> Cc: Johan Hovold <johan@kernel.org>
>> Cc: Hans de Goede <hdegoede@redhat.com>
>> ---
>> 
>> Hi,
>> 
>> The patch has been updated based on feedback recieved on the RFC[0].
>> 
>> Please consider merging if there are no objections.
>> 
>> Thanks,
>> Punit
>> 
>> [0] https://www.spinics.net/lists/linux-serial/msg36646.html
>> 
>>  drivers/tty/serdev/core.c | 10 ++++++++++
>>  1 file changed, 10 insertions(+)
>> 
>> diff --git a/drivers/tty/serdev/core.c b/drivers/tty/serdev/core.c
>> index 226adeec2aed..0d64fb7d4f36 100644
>> --- a/drivers/tty/serdev/core.c
>> +++ b/drivers/tty/serdev/core.c
>> @@ -663,6 +663,12 @@ static acpi_status acpi_serdev_register_device(struct serdev_controller *ctrl,
>>  	return AE_OK;
>>  }
>>  
>> +static const struct acpi_device_id serdev_blacklist_devices[] = {
>
> s/serdev_blacklist_devices/serdev_blacklist/acpi_devices/  ?
>
> This is an acpi-specific thing, not a generic tty thing.
>
> thanks,
>
> greg k-h

Re: [PATCH] serdev: Don't claim unsupported serial devices

[Johan Hovold]

On Wed, Dec 18, 2019 at 03:56:46PM +0900, Punit Agrawal wrote:
> Serdev sub-system claims all serial devices that are not already
> enumerated. As a result, no device node is created for serial port on
> certain boards such as the Apollo Lake based UP2. This has the
> unintended consequence of not being able to raise the login prompt via
> serial connection.
> 
> Introduce a blacklist to reject devices that should not be treated as
> a serdev device. Add the Intel HS UART peripheral ids to the blacklist
> to bring back serial port on SoCs carrying them.
> 
> Cc: stable@vger.kernel.org
> Signed-off-by: Punit Agrawal <punit1.agrawal@toshiba.co.jp>
> Cc: Rob Herring <robh@kernel.org>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Johan Hovold <johan@kernel.org>
> Cc: Hans de Goede <hdegoede@redhat.com>
> ---
> 
> Hi,
> 
> The patch has been updated based on feedback recieved on the RFC[0].
> 
> Please consider merging if there are no objections.

Rafael, I vaguely remember you arguing for a white list when we
discussed this at some conference. Do you have any objections to the
blacklist approach taken here?

> [0] https://www.spinics.net/lists/linux-serial/msg36646.html
> 
>  drivers/tty/serdev/core.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/drivers/tty/serdev/core.c b/drivers/tty/serdev/core.c
> index 226adeec2aed..0d64fb7d4f36 100644
> --- a/drivers/tty/serdev/core.c
> +++ b/drivers/tty/serdev/core.c
> @@ -663,6 +663,12 @@ static acpi_status acpi_serdev_register_device(struct serdev_controller *ctrl,
>  	return AE_OK;
>  }
>  
> +static const struct acpi_device_id serdev_blacklist_devices[] = {
> +	{"INT3511", 0},
> +	{"INT3512", 0},

Nit: Would you mind adding a space after { and before }?

> +	{ },
> +};

Johan

Re: [PATCH] serdev: Don't claim unsupported serial devices

[Punit Agrawal]

Hi Johan,

Johan Hovold <johan@kernel.org> writes:

> On Wed, Dec 18, 2019 at 03:56:46PM +0900, Punit Agrawal wrote:
>> Serdev sub-system claims all serial devices that are not already
>> enumerated. As a result, no device node is created for serial port on
>> certain boards such as the Apollo Lake based UP2. This has the
>> unintended consequence of not being able to raise the login prompt via
>> serial connection.
>> 
>> Introduce a blacklist to reject devices that should not be treated as
>> a serdev device. Add the Intel HS UART peripheral ids to the blacklist
>> to bring back serial port on SoCs carrying them.
>> 
>> Cc: stable@vger.kernel.org
>> Signed-off-by: Punit Agrawal <punit1.agrawal@toshiba.co.jp>
>> Cc: Rob Herring <robh@kernel.org>
>> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>> Cc: Johan Hovold <johan@kernel.org>
>> Cc: Hans de Goede <hdegoede@redhat.com>
>> ---
>> 
>> Hi,
>> 
>> The patch has been updated based on feedback recieved on the RFC[0].
>> 
>> Please consider merging if there are no objections.
>
> Rafael, I vaguely remember you arguing for a white list when we
> discussed this at some conference. Do you have any objections to the
> blacklist approach taken here?
>
>> [0] https://www.spinics.net/lists/linux-serial/msg36646.html
>> 
>>  drivers/tty/serdev/core.c | 10 ++++++++++
>>  1 file changed, 10 insertions(+)
>> 
>> diff --git a/drivers/tty/serdev/core.c b/drivers/tty/serdev/core.c
>> index 226adeec2aed..0d64fb7d4f36 100644
>> --- a/drivers/tty/serdev/core.c
>> +++ b/drivers/tty/serdev/core.c
>> @@ -663,6 +663,12 @@ static acpi_status acpi_serdev_register_device(struct serdev_controller *ctrl,
>>  	return AE_OK;
>>  }
>>  
>> +static const struct acpi_device_id serdev_blacklist_devices[] = {
>> +	{"INT3511", 0},
>> +	{"INT3512", 0},
>
> Nit: Would you mind adding a space after { and before }?

Sure - no problem. I'll include it in the next posting.

Thanks for having a look.

>
>> +	{ },
>> +};
>
> Johan

Re: [PATCH] serdev: Don't claim unsupported serial devices

[Rafael J. Wysocki]

On Wed, Dec 18, 2019 at 9:56 AM Johan Hovold <johan@kernel.org> wrote:
>
> On Wed, Dec 18, 2019 at 03:56:46PM +0900, Punit Agrawal wrote:
> > Serdev sub-system claims all serial devices that are not already
> > enumerated. As a result, no device node is created for serial port on
> > certain boards such as the Apollo Lake based UP2. This has the
> > unintended consequence of not being able to raise the login prompt via
> > serial connection.
> >
> > Introduce a blacklist to reject devices that should not be treated as
> > a serdev device. Add the Intel HS UART peripheral ids to the blacklist
> > to bring back serial port on SoCs carrying them.
> >
> > Cc: stable@vger.kernel.org
> > Signed-off-by: Punit Agrawal <punit1.agrawal@toshiba.co.jp>
> > Cc: Rob Herring <robh@kernel.org>
> > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> > Cc: Johan Hovold <johan@kernel.org>
> > Cc: Hans de Goede <hdegoede@redhat.com>
> > ---
> >
> > Hi,
> >
> > The patch has been updated based on feedback recieved on the RFC[0].
> >
> > Please consider merging if there are no objections.
>
> Rafael, I vaguely remember you arguing for a white list when we
> discussed this at some conference. Do you have any objections to the
> blacklist approach taken here?

As a rule, I prefer whitelisting, because it only enables the feature
for systems where it has been tested and confirmed to work.

However, if you are convinced that in this particular case the feature
should work on the vast majority of systems with a few possible
exceptions, blacklisting is fine too.

It all depends on what the majority is, at least in principle.

Re: [PATCH] serdev: Don't claim unsupported serial devices

[Johan Hovold]

On Thu, Dec 19, 2019 at 09:39:57AM +0100, Rafael J. Wysocki wrote:
> On Wed, Dec 18, 2019 at 9:56 AM Johan Hovold <johan@kernel.org> wrote:
> >
> > On Wed, Dec 18, 2019 at 03:56:46PM +0900, Punit Agrawal wrote:
> > > Serdev sub-system claims all serial devices that are not already
> > > enumerated. As a result, no device node is created for serial port on
> > > certain boards such as the Apollo Lake based UP2. This has the
> > > unintended consequence of not being able to raise the login prompt via
> > > serial connection.
> > >
> > > Introduce a blacklist to reject devices that should not be treated as
> > > a serdev device. Add the Intel HS UART peripheral ids to the blacklist
> > > to bring back serial port on SoCs carrying them.
> > >
> > > Cc: stable@vger.kernel.org
> > > Signed-off-by: Punit Agrawal <punit1.agrawal@toshiba.co.jp>
> > > Cc: Rob Herring <robh@kernel.org>
> > > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> > > Cc: Johan Hovold <johan@kernel.org>
> > > Cc: Hans de Goede <hdegoede@redhat.com>
> > > ---
> > >
> > > Hi,
> > >
> > > The patch has been updated based on feedback recieved on the RFC[0].
> > >
> > > Please consider merging if there are no objections.
> >
> > Rafael, I vaguely remember you arguing for a white list when we
> > discussed this at some conference. Do you have any objections to the
> > blacklist approach taken here?
> 
> As a rule, I prefer whitelisting, because it only enables the feature
> for systems where it has been tested and confirmed to work.
> 
> However, if you are convinced that in this particular case the feature
> should work on the vast majority of systems with a few possible
> exceptions, blacklisting is fine too.
> 
> It all depends on what the majority is, at least in principle.

Ok, thanks. I don't have a preference either way in this case simply
because I don't know the distribution you refer to.

But if Hans thinks blacklisting is the way to go then let's do that. We
haven't had that many reports about this, but if that were to change
down the line, I guess we can always switch to whitelisting.

Punit, feel free to add my

Acked-by: Johan Hovold <johan@kernel.org>

after addressing the review comments you've gotten so far.

Johan

Re: [PATCH] serdev: Don't claim unsupported serial devices

[Punit Agrawal]

Johan Hovold <johan@kernel.org> writes:

> On Thu, Dec 19, 2019 at 09:39:57AM +0100, Rafael J. Wysocki wrote:
>> On Wed, Dec 18, 2019 at 9:56 AM Johan Hovold <johan@kernel.org> wrote:
>> >
>> > On Wed, Dec 18, 2019 at 03:56:46PM +0900, Punit Agrawal wrote:
>> > > Serdev sub-system claims all serial devices that are not already
>> > > enumerated. As a result, no device node is created for serial port on
>> > > certain boards such as the Apollo Lake based UP2. This has the
>> > > unintended consequence of not being able to raise the login prompt via
>> > > serial connection.
>> > >
>> > > Introduce a blacklist to reject devices that should not be treated as
>> > > a serdev device. Add the Intel HS UART peripheral ids to the blacklist
>> > > to bring back serial port on SoCs carrying them.
>> > >
>> > > Cc: stable@vger.kernel.org
>> > > Signed-off-by: Punit Agrawal <punit1.agrawal@toshiba.co.jp>
>> > > Cc: Rob Herring <robh@kernel.org>
>> > > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>> > > Cc: Johan Hovold <johan@kernel.org>
>> > > Cc: Hans de Goede <hdegoede@redhat.com>
>> > > ---
>> > >
>> > > Hi,
>> > >
>> > > The patch has been updated based on feedback recieved on the RFC[0].
>> > >
>> > > Please consider merging if there are no objections.
>> >
>> > Rafael, I vaguely remember you arguing for a white list when we
>> > discussed this at some conference. Do you have any objections to the
>> > blacklist approach taken here?
>> 
>> As a rule, I prefer whitelisting, because it only enables the feature
>> for systems where it has been tested and confirmed to work.
>> 
>> However, if you are convinced that in this particular case the feature
>> should work on the vast majority of systems with a few possible
>> exceptions, blacklisting is fine too.
>> 
>> It all depends on what the majority is, at least in principle.
>
> Ok, thanks. I don't have a preference either way in this case simply
> because I don't know the distribution you refer to.
>
> But if Hans thinks blacklisting is the way to go then let's do that. We
> haven't had that many reports about this, but if that were to change
> down the line, I guess we can always switch to whitelisting.
>
> Punit, feel free to add my
>
> Acked-by: Johan Hovold <johan@kernel.org>
>
> after addressing the review comments you've gotten so far.

Thanks Johan.

I will post a new version with the updates and acks.

Re: [PATCH] serdev: Don't claim unsupported serial devices

[Hans de Goede]

Hi,

On 18-12-2019 07:56, Punit Agrawal wrote:
> Serdev sub-system claims all serial devices that are not already
> enumerated. As a result, no device node is created for serial port on
> certain boards such as the Apollo Lake based UP2. This has the
> unintended consequence of not being able to raise the login prompt via
> serial connection.
> 
> Introduce a blacklist to reject devices that should not be treated as
> a serdev device. Add the Intel HS UART peripheral ids to the blacklist
> to bring back serial port on SoCs carrying them.
> 
> Cc: stable@vger.kernel.org
> Signed-off-by: Punit Agrawal <punit1.agrawal@toshiba.co.jp>
> Cc: Rob Herring <robh@kernel.org>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Johan Hovold <johan@kernel.org>
> Cc: Hans de Goede <hdegoede@redhat.com>

Thank you for addressing this long standing issue.

The basic approach here looks good to me, once the minor
comments from other reviewers are addressed you can add my:

Acked-by: Hans de Goede <hdegoede@redhat.com>

to the next version.

Regards,

Hans



> ---
> 
> Hi,
> 
> The patch has been updated based on feedback recieved on the RFC[0].
> 
> Please consider merging if there are no objections.
> 
> Thanks,
> Punit
> 
> [0] https://www.spinics.net/lists/linux-serial/msg36646.html
> 
>   drivers/tty/serdev/core.c | 10 ++++++++++
>   1 file changed, 10 insertions(+)
> 
> diff --git a/drivers/tty/serdev/core.c b/drivers/tty/serdev/core.c
> index 226adeec2aed..0d64fb7d4f36 100644
> --- a/drivers/tty/serdev/core.c
> +++ b/drivers/tty/serdev/core.c
> @@ -663,6 +663,12 @@ static acpi_status acpi_serdev_register_device(struct serdev_controller *ctrl,
>   	return AE_OK;
>   }
>   
> +static const struct acpi_device_id serdev_blacklist_devices[] = {
> +	{"INT3511", 0},
> +	{"INT3512", 0},
> +	{ },
> +};
> +
>   static acpi_status acpi_serdev_add_device(acpi_handle handle, u32 level,
>   					  void *data, void **return_value)
>   {
> @@ -675,6 +681,10 @@ static acpi_status acpi_serdev_add_device(acpi_handle handle, u32 level,
>   	if (acpi_device_enumerated(adev))
>   		return AE_OK;
>   
> +	/* Skip if black listed */
> +	if (!acpi_match_device_ids(adev, serdev_blacklist_devices))
> +		return AE_OK;
> +
>   	if (acpi_serdev_check_resources(ctrl, adev))
>   		return AE_OK;
>   
> 

Re: [PATCH] serdev: Don't claim unsupported serial devices

[Punit Agrawal]

Hans de Goede <hdegoede@redhat.com> writes:

> Hi,
>
> On 18-12-2019 07:56, Punit Agrawal wrote:
>> Serdev sub-system claims all serial devices that are not already
>> enumerated. As a result, no device node is created for serial port on
>> certain boards such as the Apollo Lake based UP2. This has the
>> unintended consequence of not being able to raise the login prompt via
>> serial connection.
>>
>> Introduce a blacklist to reject devices that should not be treated as
>> a serdev device. Add the Intel HS UART peripheral ids to the blacklist
>> to bring back serial port on SoCs carrying them.
>>
>> Cc: stable@vger.kernel.org
>> Signed-off-by: Punit Agrawal <punit1.agrawal@toshiba.co.jp>
>> Cc: Rob Herring <robh@kernel.org>
>> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>> Cc: Johan Hovold <johan@kernel.org>
>> Cc: Hans de Goede <hdegoede@redhat.com>
>
> Thank you for addressing this long standing issue.

I am surprised there hasn't been more people complaining! Maybe even on
x86 mainline isn't that widely used on development boards.

> The basic approach here looks good to me, once the minor
> comments from other reviewers are addressed you can add my:
>
> Acked-by: Hans de Goede <hdegoede@redhat.com>

Thanks!

[...]

Re: [PATCH] serdev: Don't claim unsupported serial devices

[Hans de Goede]

Hi,

On 19-12-2019 01:37, Punit Agrawal wrote:
> Hans de Goede <hdegoede@redhat.com> writes:
> 
>> Hi,
>>
>> On 18-12-2019 07:56, Punit Agrawal wrote:
>>> Serdev sub-system claims all serial devices that are not already
>>> enumerated. As a result, no device node is created for serial port on
>>> certain boards such as the Apollo Lake based UP2. This has the
>>> unintended consequence of not being able to raise the login prompt via
>>> serial connection.
>>>
>>> Introduce a blacklist to reject devices that should not be treated as
>>> a serdev device. Add the Intel HS UART peripheral ids to the blacklist
>>> to bring back serial port on SoCs carrying them.
>>>
>>> Cc: stable@vger.kernel.org
>>> Signed-off-by: Punit Agrawal <punit1.agrawal@toshiba.co.jp>
>>> Cc: Rob Herring <robh@kernel.org>
>>> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>>> Cc: Johan Hovold <johan@kernel.org>
>>> Cc: Hans de Goede <hdegoede@redhat.com>
>>
>> Thank you for addressing this long standing issue.
> 
> I am surprised there hasn't been more people complaining! Maybe even on
> x86 mainline isn't that widely used on development boards.

I think it is also a case of there not being that manu x86 development
boards.

Regards,

Hans