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

[Maximilian Luz]

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