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

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

On 20-02-2026 10:32, Suraj Kandpal wrote:
> Whenever the minimum brightness is reported as 0 there are chances
> we maybe sometimes end up with blank screen. This confuses the user
> into thinking the display is acting weird. This occurs in eDP 1.5 when
> we are using PANEL_LUMINANCE_OVERRIDE mode to mainpulate brightness
> via luminance values. Make sure if minimum luminance range is 0 we
> program default value to max in case 0 is returned from luminance
> registers.

Changes looks good!

Can this header and the patch comment be changed?
drm/i915/backlight: use default/max brightness on backlight init

If the brightness fetched from VBT/previous state is 0 on backlight 
initialization,
then set the brightness to a default/max value.

With the above change
Reviewed-by: Arun R Murthy <arun.r.murthy@intel.com>


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>
> ---
> v1 -> v2:
> - Let users set brightness to 0, make it so that it's just not
> done by default (Arun)
>
>   drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c | 4 ++++
>   1 file changed, 4 insertions(+)
>
> 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..c40ce310ad97 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
> @@ -564,6 +564,8 @@ static int intel_dp_aux_vesa_setup_backlight(struct intel_connector *connector,
>   		}
>   		panel->backlight.level = intel_dp_aux_vesa_get_backlight(connector, 0);
>   		panel->backlight.enabled = panel->backlight.level != 0;
> +		if (!panel->backlight.level)
> +			panel->backlight.level = panel->backlight.max;
>   		drm_dbg_kms(display->drm,
>   			    "[CONNECTOR:%d:%s] AUX VESA Nits backlight level is controlled through DPCD\n",
>   			    connector->base.base.id, connector->base.name);
> @@ -573,6 +575,8 @@ static int intel_dp_aux_vesa_setup_backlight(struct intel_connector *connector,
>   		if (current_mode == DP_EDP_BACKLIGHT_CONTROL_MODE_DPCD) {
>   			panel->backlight.level = current_level;
>   			panel->backlight.enabled = panel->backlight.level != 0;
> +			if (!panel->backlight.level)
> +				panel->backlight.level = panel->backlight.max;
>   		} else {
>   			panel->backlight.level = panel->backlight.max;
>   			panel->backlight.enabled = false;