Re: [PATCH v5] ACPI: video: force native backlight on Dell OptiPlex AIO 7410 35W

[Rafael J. Wysocki (Intel)]

On Mon, Oct 12, 2026 at 4:55 PM Hans de Goede <hansg@xxxxxxxxxx> wrote:
>
> Hi,
>
> On 10-Oct-26 14:48, chitranshmandhaniya@xxxxxxxxx wrote:
> > From: Chitransh Mandhaniya <Chitransh_Mandhaniya@xxxxxxxx>
> >
> > The Dell OptiPlex AIO 7410 35W (board 01KP8D) declares DELL0501 in its
> > ACPI DSDT (status = 0x0F) even though no UART scalar board is physically
> > present. This causes acpi_video_get_backlight_type() to return
> > acpi_backlight_dell_uart, which makes i915 skip registering
> > intel_backlight. The dell-uart-backlight driver then times out talking
> > to the absent board and the probe fails, leaving the machine with zero
> > backlight control.
> >
> > A BIOS update fixes this on some models (e.g. OptiPlex 7420, board
> > 0914RT) by setting DELL0501 _STA to 0, but Dell has not shipped a
> > corrected BIOS for the 7410 even in the latest release (1.37.0,
> > 2026-05-28).
> >
> > Add a DMI quirk to force native backlight on this model so that i915
> > registers intel_backlight and brightness control works out of the box.
> >
> > Tested on:
> >   - OptiPlex AIO 7410 35W (01KP8D, BIOS 1.37.0) -- confirmed
> >     acpi_backlight=native produces working intel_backlight (raw,
> >     max=96000), DMI quirk has the same effect.
> >   - OptiPlex AIO 7420 35W (0914RT, BIOS 1.27.0) -- DELL0501 absent in
> >     updated BIOS, intel_backlight works natively (no regression).
> >
> > Signed-off-by: Chitransh Mandhaniya <Chitransh_Mandhaniya@xxxxxxxx>
>
> Thanks, patch looks good to me:
>
> Reviewed-by: Hans de Goede <johannes.goede@xxxxxxxxxxxxxxxx>

Applied as 7.4 material, thanks!