linux-kernel - Re: [PATCH] platform/x86: Add Driver to set up lid GPEs on MS Surface device

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Date:   Tue, 8 Sep 2020 22:19:27 +0200
From:   Maximilian Luz <luzmaximilian@...il.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Darren Hart <dvhart@...radead.org>,
        Andy Shevchenko <andy@...radead.org>,
        Hans de Goede <hdegoede@...hat.com>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Gayatri Kammela <gayatri.kammela@...el.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>,
        Platform Driver <platform-driver-x86@...r.kernel.org>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] platform/x86: Add Driver to set up lid GPEs on MS Surface
 device

On 9/8/20 8:40 PM, Andy Shevchenko wrote:
> On Tue, Sep 8, 2020 at 8:20 PM Maximilian Luz <luzmaximilian@...il.com> wrote:

...

>> +       .gpe_number = 0x17,
>> +       .gpe_number = 0x4D,
>> +       .gpe_number = 0x4F,
>> +       .gpe_number = 0x57,
> 
>  From where these numbers come from? Can we get them from firmware (ACPI)?

Yes, they are obtained from ACPI/the DSDT. Specifically from the name of
the GPE handler notifying the lid device. See [1] for a repo full of
Surface ACPI dumps (source for this). I'll add a comment pointing this out
in v2.

[1]: https://github.com/linux-surface/acpidumps

...

>> +static int surface_gpe_probe(struct platform_device *pdev)
>> +{
>> +       const struct surface_lid_device *lid;
>> +       int status;
>> +
> 
>> +       lid = dev_get_platdata(&pdev->dev);
>> +       if (!lid)
>> +               return -ENODEV;
> 
> Can we use software nodes?

As far as I can tell this would work via fwnode_create_software_node /
fwnode_remove_software_node and device properties? I don't seem to find
much documentation on this (there doesn't seem to be an entry for
software nodes in the official docs?), but I think I should be able to
make this work.

>> +       status = acpi_mark_gpe_for_wake(NULL, lid->gpe_number);
>> +       if (status) {
>> +               dev_err(&pdev->dev, "failed to mark GPE for wake: %d\n", status);
>> +               return -EINVAL;
>> +       }
>> +
> 
>> +       status = acpi_enable_gpe(NULL, lid->gpe_number);
> 
> Did I miss anything or all calls of enable / disable GPE are using
> NULL as a first parameter? What the point in such case?

As far as I can tell, some of the more generic uses have a non-NULL
gpe_device parameter (acpi/device_pm.c, acpi/wakeup.c) and NULL just
means index-0/main device? Not an expert on that though, so probably
just ignore me here and let the ACPI guys answer this.

...

>> +MODULE_ALIAS("dmi:*:svnMicrosoftCorporation:pnSurfacePro:*");
>> +MODULE_ALIAS("dmi:*:svnMicrosoftCorporation:pnSurfacePro4:*");
> 
> Can simply
> 
> MODULE_ALIAS("dmi:*:svnMicrosoftCorporation:pnSurface*:*");
> 
> work?

Depends on your preference, really. That would also auto-load the module
on Surface Pro 3 and earlier devices (just won't do anything on those).
So it's a trade-off between unnecessary loading of the module and
maintainability/readability. Let me know what you prefer and I'll switch
to that.

Style and other issues are noted, I'll fix them for v2.

Regards,
Max