linux-kernel - Re: [PATCH v1 5/7] surface: surface3_power: Use ACPI

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Date:   Tue, 12 Oct 2021 21:11:15 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Maximilian Luz <luzmaximilian@...il.com>
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Linux ACPI <linux-acpi@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Hans de Goede <hdegoede@...hat.com>,
        Mark Gross <mgross@...ux.intel.com>,
        Platform Driver <platform-driver-x86@...r.kernel.org>
Subject: Re: [PATCH v1 5/7] surface: surface3_power: Use ACPI_COMPANION() directly

On Tue, Oct 12, 2021 at 8:21 PM Maximilian Luz <luzmaximilian@...il.com> wrote:
>
> On 10/12/21 19:46, Rafael J. Wysocki wrote:
> > From: Rafael J. Wysocki <rafael@...nel.org>
> >
> > The ACPI_HANDLE() macro is a wrapper arond the ACPI_COMPANION()
> > macro and the ACPI handle produced by the former comes from the
> > ACPI device object produced by the latter, so it is way more
> > straightforward to evaluate the latter directly instead of passing
> > the handle produced by the former to acpi_bus_get_device().
> >
> > Modify mshw0011_notify() accordingly (no intentional functional
> > impact).
> >
> > Signed-off-by: Rafael J. Wysocki <rafael@...nel.org>
>
> Looks mostly good to me, small comment/question inline.
>
> > ---
> >   drivers/platform/surface/surface3_power.c |    9 ++++-----
> >   1 file changed, 4 insertions(+), 5 deletions(-)
> >
> > Index: linux-pm/drivers/platform/surface/surface3_power.c
> > ===================================================================
> > --- linux-pm.orig/drivers/platform/surface/surface3_power.c
> > +++ linux-pm/drivers/platform/surface/surface3_power.c
> > @@ -160,15 +160,14 @@ mshw0011_notify(struct mshw0011_data *cd
> >   {
> >       union acpi_object *obj;
> >       struct acpi_device *adev;
> > -     acpi_handle handle;
> >       unsigned int i;
> >
> > -     handle = ACPI_HANDLE(&cdata->adp1->dev);
> > -     if (!handle || acpi_bus_get_device(handle, &adev))
> > +     adev = ACPI_COMPANION(&cdata->adp1->dev);
> > +     if (!adev)
> >               return -ENODEV;
>
> Do we need to get the ACPI device (adev) here? To me it looks like only
> its handle is actually used so why not keep ACPI_HANDLE() and remove the
> acpi_bus_get_device() call instead?

It actually doesn't really matter, but you're right,
acpi_bus_get_device() is simply redundant here, so ACPI_HANDLE() is
sufficient.

I'll send a v2 of this one.

> >
> > -     obj = acpi_evaluate_dsm_typed(handle, &mshw0011_guid, arg1, arg2, NULL,
> > -                                   ACPI_TYPE_BUFFER);
> > +     obj = acpi_evaluate_dsm_typed(adev->handle, &mshw0011_guid, arg1, arg2,
> > +                                   NULL, ACPI_TYPE_BUFFER);
> >       if (!obj) {
> >               dev_err(&cdata->adp1->dev, "device _DSM execution failed\n");
> >               return -ENODEV;
> >
> >
> >
>
> Regards,
> Max