linux-kernel - Re: [PATCH 2/2] platform/surface: surfacepro3

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Date:   Tue, 1 Mar 2022 22:03:59 +0100
From:   Hans de Goede <hdegoede@...hat.com>
To:     Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Sachi King <nakato@...ato.io>, Chen Yu <yu.c.chen@...el.com>,
        Mark Gross <markgross@...nel.org>,
        Maximilian Luz <luzmaximilian@...il.com>,
        Platform Driver <platform-driver-x86@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] platform/surface: surfacepro3_button: don't load on
 amd variant

Hi All,

On 3/1/22 22:01, Dmitry Torokhov wrote:
> On Tue, Nov 09, 2021 at 11:12:34AM +0200, Andy Shevchenko wrote:
>> On Tue, Nov 9, 2021 at 10:11 AM Sachi King <nakato@...ato.io> wrote:
>>>
>>> The AMD variant of the Surface Laptop report 0 for their OEM platform
>>> revision.  The Surface devices that require the surfacepro3_button
>>> driver do not have the _DSM that gets the OEM platform revision.  If the
>>> method does not exist, load surfacepro3_button.
>>
>> ...
>>
>>>   * Surface Pro 4 and Surface Book 2 / Surface Pro 2017 use the same device
>>>   * ID (MSHW0040) for the power/volume buttons. Make sure this is the right
>>> - * device by checking for the _DSM method and OEM Platform Revision.
>>> + * device by checking for the _DSM method and OEM Platform Revision DSM
>>> + * function.
>>
>> Not sure what this change means (not a native speaker).
>>
>> ...
>>
>>> -       dev_dbg(&dev->dev, "OEM Platform Revision %llu\n", oem_platform_rev);
>>
>> I think this is useful to have.
>>
>> What about leaving it as is for debugging purposes and just replacing
>> the last test?
> 
> I agree it is nice to be able to print it for debug purposes, but it has
> to be fetched separately, as with the proposed change we are not reading
> it.
> 
> If I am understanding the change it wants to call acpi_dsm_check()
> to verify whether MSHW0040_DSM_GET_OMPR function exists at all (which is
> done by reading _DSM MSHW0040_DSM_UUID, revision MSHW0040_DSM_REVISION,
> function 0. Only if function 0 indicates that function
> MSHW0040_DSM_GET_OMPR is supported in this _DSM, we can read it to get
> the real version number, which can be 0.
> 
> Treating 0 as an invalid version as it was done in original change is
> wrong.
> 
> I propose we combine the old and new code, call acpi_dsm_check() and
> bail if it returns false, otherwise proceed to calling
> acpi_evaluate_dsm_typed() and dev_dbg() the version.
> 
> Sachi, are you going to update the patch? You do not need to adjust the
> surface driver as Hans is getting rid of it.

Right, for more info on that see:

https://lore.kernel.org/linux-input/20220224110241.9613-1-hdegoede@redhat.com/

Regards,

Hans