Re: [PATCH] platform/x86: Add and use a dual_accel_detect() helper

[Andy Shevchenko <andy.shevchenko@gmail.com>]

On Thu, Jul 29, 2021 at 11:45 AM Hans de Goede <hdegoede@redhat.com> wrote:
>
> Hi,
>
> On 7/29/21 10:37 AM, Andy Shevchenko wrote:
> > On Thu, Jul 29, 2021 at 11:21 AM Hans de Goede <hdegoede@redhat.com> wrote:
> >>
> >> Various 360 degree hinges (yoga) style 2-in-1 devices use 2 accelerometers
> >> to allow the OS to determine the angle between the display and the base of
> >> the device.
> >>
> >> On Windows these are read by a special HingeAngleService process which
> >> calls undocumented ACPI methods, to let the firmware know if the 2-in-1 is
> >> in tablet- or laptop-mode. The firmware may use this to disable the kbd and
> >> touchpad to avoid spurious input in tablet-mode as well as to report
> >> SW_TABLET_MODE info to the OS.
> >>
> >> Since Linux does not call these undocumented methods, the SW_TABLET_MODE
> >> info reported by various pdx86 drivers is incorrect on these devices.
> >>
> >> Before this commit the intel-hid and thinkpad_acpi code already had 2
> >> hardcoded checks for ACPI hardware-ids of dual-accel sensors to avoid
> >> reporting broken info.
> >>
> >> And now we also have a bug-report about the same problem in the intel-vbtn
> >> code. Since there are at least 3 different ACPI hardware-ids in play, add
> >> a new dual_accel_detect() helper which checks for all 3, rather then
> >> adding different hardware-ids to the drivers as bug-reports trickle in.
> >> Having shared code which checks all known hardware-ids is esp. important
> >> for the intel-hid and intel-vbtn drivers as these are generic drivers
> >> which are used on a lot of devices.
> >>
> >> The BOSC0200 hardware-id requires special handling, because often it is
> >> used for a single-accelerometer setup. Only in a few cases it refers to
> >> a dual-accel setup, in which case there will be 2 I2cSerialBus resources
> >> in the device's resource-list, so the helper checks for this.
> >
> > ...
> >
> >> +static int dual_accel_i2c_resource_count(struct acpi_resource *ares, void *data)
> >> +{
> >> +       struct acpi_resource_i2c_serialbus *sb;
> >> +       int *count = data;
> >> +
> >> +       if (i2c_acpi_get_i2c_resource(ares, &sb))
> >> +               *count = *count + 1;
> >> +
> >> +       return 1;
> >> +}
> >
> > It will be a third copy of this in the kernel.
> > Let's put it to i2c.h or somewhere available for all these users.
> >
> >> +
> >> +static int dual_accel_i2c_client_count(struct acpi_device *adev)
> >> +{
> >> +       int ret, count = 0;
> >> +       LIST_HEAD(r);
> >> +
> >> +       ret = acpi_dev_get_resources(adev, &r, dual_accel_i2c_resource_count, &count);
> >> +       if (ret < 0)
> >> +               return ret;
> >> +
> >> +       acpi_dev_free_resource_list(&r);
> >> +       return count;
> >> +}
> >
> > So does this.
> >
> > Taking into account that this is a bug fix, I'm okay if you do above
> > as an additional patch (or patches) on top of this.
>
> Right, I had a note about this behind the cut (---) line, but I dropped
> the patch and git-am-ed it while reworking my tree for some other issue
> dropping the note (sorry), the note was:
>
> """
> ---
> Note the counting of the number of I2cSerialBus resources in an
> ACPI-device's resource-list is becoming a common pattern. I plan
> to add a new shared helper for this in a follow-up patch-set.
> I've deliberately not made use of such a new helper in this patch
> for easier backporting to the stable series.
> """
>
> In other words, I fully agree. I've already added an item to my
> TODO list about doing a followup series to replace the 3 copies in:

With this promise taken
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>

>  drivers/platform/x86/dual_accel_detect.h
>  drivers/platform/x86/i2c-multi-instantiate.c
>  drivers/platform/x86/intel/int33fe/intel_cht_int33fe_common.c
>
> With a new helper in drivers/i2c/i2c-core-acpi.c, like the
> i2c_acpi_get_i2c_resource() helper which was recently added.


-- 
With Best Regards,
Andy Shevchenko