Hi,
On 10/24/22 15:32, Dmitry Osipenko wrote:
> Chromebooks don't have backlight in ACPI table, they suppose to use
> native backlight in this case. Check presence of the CrOS embedded
> controller ACPI device and prefer the native backlight if EC found.
Thank you for this patch!
> Suggested-by: Hans de Goede <hdegoede@xxxxxxxxxx>
> Fixes: b1d36e73cc1c ("drm/i915: Don't register backlight when another backlight should be used (v2)")
> Signed-off-by: Dmitry Osipenko <dmitry.osipenko@xxxxxxxxxxxxx>
> ---
> drivers/acpi/video_detect.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/drivers/acpi/video_detect.c b/drivers/acpi/video_detect.c
> index 0d9064a9804c..8ed5021de6fb 100644
> --- a/drivers/acpi/video_detect.c
> +++ b/drivers/acpi/video_detect.c
> @@ -668,6 +668,11 @@ static const struct dmi_system_id video_detect_dmi_table[] = {
> { },
> };
>
> +static bool google_cros_ec_present(void)
> +{
> + return acpi_dev_found("GOOG0004");
> +}
> +
> /*
> * Determine which type of backlight interface to use on this system,
> * First check cmdline, then dmi quirks, then do autodetect.
> @@ -730,6 +735,9 @@ static enum acpi_backlight_type __acpi_video_get_backlight_type(bool native)
> return acpi_backlight_video;
> }
>
> + if (google_cros_ec_present())
> + return acpi_backlight_native;
> +
Nice, a couple of remarks:
1. Maybe add a small comment explaining why, like all the other tests in the function have a small comment ?
2. I think it would be better to do:
if (google_cros_ec_present() && native_available)
return acpi_backlight_native;
I can e.g. imagine in the future some chromebooks where for some reason native
GPU backlight control is not available using the EC for backlight control
and then having the chrome-ec code register a backlight with "vendor" type ?
3. This will also trigger on the Framework laptops and possible other new
non Chromebook designs which choose to use the Chrome EC code for their EC,
I don't expect these devices to get to this point of __acpi_video_get_backlight_type()
(they will hit the earlier acpi_video / native paths) but still I want to
at least point this out in case someone sees a potential issue with this?
If you can address 1. and 2. from above (or explain why 2. is a bad idea)
then I believe that the next version of this can get merged to resolve
the chromebook backlight issues introduced in 6.1-rc1, thank you!
> /* No ACPI video (old hw), use vendor specific fw methods. */
> return acpi_backlight_vendor;
> }
Regards,
Hans
