Re: [PATCH 1/8] drm/i915/backlight: Avoid 0 brightness for VESA AUX backlight

["Murthy, Arun R" <arun.r.murthy@intel.com>]

On 13-02-2026 14:46, Suraj Kandpal wrote:
> Whenever the minimum brightness is reported as 0 there are chances
> we maybe sometimes end up with blank screen.
maybe->may
Please reframe
>   This confuses the user
> into thinking the display is acting weird. This occurs in eDP 1.5 when
> we are PANEL_LUMINANCE_OVERRIDE
in PANEL_LUMINANCE_OVERRIDE
>   mode to mainpulate brightness via luminance
> values. Make sure if minimum luminance range is 0 we program
> it to 10% of max luminance range.
0 nits for OLED panel is a valid value right?
Instead better to have a default brightness if no brightness is parsed 
from the vbt and the default brightness can be max_brightness.

Thanks and Regards,
Arun R Murthy
--------------------

>
> Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/15671
> Signed-off-by: Suraj Kandpal <suraj.kandpal@intel.com>
> ---
>   .../gpu/drm/i915/display/intel_dp_aux_backlight.c  | 14 +++++++++++---
>   1 file changed, 11 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
> index eb05ef4bd9f6..f1811beee25f 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
> @@ -456,7 +456,11 @@ static u32 intel_dp_aux_vesa_get_backlight(struct intel_connector *connector, en
>   		}
>   
>   		val |= buf[0] | buf[1] << 8 | buf[2] << 16;
> -		return val / 1000;
> +		val = val / 1000;
> +		if (!val)
> +			return panel->backlight.min;
> +
> +		return val;
>   	}
>   
>   	return connector->panel.backlight.level;
> @@ -557,10 +561,14 @@ static int intel_dp_aux_vesa_setup_backlight(struct intel_connector *connector,
>   	if (panel->backlight.edp.vesa.info.luminance_set) {
>   		if (luminance_range->max_luminance) {
>   			panel->backlight.max = panel->backlight.edp.vesa.info.max;
> -			panel->backlight.min = luminance_range->min_luminance;
> +			if (luminance_range->min_luminance)
> +				panel->backlight.min = luminance_range->min_luminance;
> +			else
> +				panel->backlight.min = (luminance_range->max_luminance * 10) / 100;
> +
>   		} else {
>   			panel->backlight.max = 512;
> -			panel->backlight.min = 0;
> +			panel->backlight.min = 51;
>   		}
>   		panel->backlight.level = intel_dp_aux_vesa_get_backlight(connector, 0);
>   		panel->backlight.enabled = panel->backlight.level != 0;