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

[Hans de Goede]

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>

Regards,

Hans




> ---
>  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 e3b69f876d24..1af14e04e597 100644
> --- a/drivers/acpi/video_detect.c
> +++ b/drivers/acpi/video_detect.c
> @@ -883,6 +883,14 @@ static const struct dmi_system_id video_detect_dmi_table[] = {
>  		DMI_MATCH(DMI_PRODUCT_NAME, "OptiPlex 7770 AIO"),
>  		},
>  	},
> +	{
> +	 .callback = video_detect_force_native,
> +	 /* Dell OptiPlex AIO 7410 35W */
> +	 .matches = {
> +		DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
> +		DMI_MATCH(DMI_PRODUCT_NAME, "OptiPlex AIO 7410 35W"),
> +		},
> +	},
>  
>  	/*
>  	 * Models which have nvidia-ec-wmi support, but should not use it.