[PATCH v2] ACPI: video: Fix missing native backlight on Chromebooks

[Hans de Goede]

Hi,

On 10/24/22 16:12, 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.
> 
> Suggested-by: Hans de Goede <hdegoede at redhat.com>
> Fixes: 2600bfa3df99 ("ACPI: video: Add acpi_video_backlight_use_native() helper")
> Signed-off-by: Dmitry Osipenko <dmitry.osipenko at collabora.com>
> ---
> 
> Changelog:
> 
> v2: - Added explanatory comment to the code and added check for the
>       native backlight presence, like was requested by Hans de Goede.

Thanks this version looks good to me:

Reviewed-by: Hans de Goede <hdegoede at redhat.com>

Rafael, can you pick this up and send it in a fixes pull-req
for 6.1 to Linus? Or shall I pick this one up and include it
in my next pull-req?

Regards,

Hans





> 
>  drivers/acpi/video_detect.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/drivers/acpi/video_detect.c b/drivers/acpi/video_detect.c
> index 0d9064a9804c..9cd8797d12bb 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 +735,13 @@ static enum acpi_backlight_type __acpi_video_get_backlight_type(bool native)
>  			return acpi_backlight_video;
>  	}
>  
> +	/*
> +	 * Chromebooks that don't have backlight handle in ACPI table
> +	 * are supposed to use native backlight if it's available.
> +	 */
> +	if (google_cros_ec_present() && native_available)
> +		return acpi_backlight_native;
> +
>  	/* No ACPI video (old hw), use vendor specific fw methods. */
>  	return acpi_backlight_vendor;
>  }