linux-kernel - RE: [PATCH 2/2] drm/i915/backlight: Add get brightness support of DPCD via AUX

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Message-ID: <DM3PPF208195D8DD3E38CF770DE7A86EFB9E31EA@DM3PPF208195D8D.namprd11.prod.outlook.com>
Date: Fri, 26 Sep 2025 09:26:40 +0000
From: "Kandpal, Suraj" <suraj.kandpal@...el.com>
To: "Aaron, Ma" <aaron.ma@...onical.com>, "dri-devel@...ts.freedesktop.org"
	<dri-devel@...ts.freedesktop.org>, "intel-gfx@...ts.freedesktop.org"
	<intel-gfx@...ts.freedesktop.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>
CC: "maarten.lankhorst@...ux.intel.com" <maarten.lankhorst@...ux.intel.com>,
	"mripard@...nel.org" <mripard@...nel.org>, "tzimmermann@...e.de"
	<tzimmermann@...e.de>, "airlied@...il.com" <airlied@...il.com>,
	"simona@...ll.ch" <simona@...ll.ch>, "jani.nikula@...ux.intel.com"
	<jani.nikula@...ux.intel.com>, "Vivi, Rodrigo" <rodrigo.vivi@...el.com>,
	"Deak, Imre" <imre.deak@...el.com>, "joonas.lahtinen@...ux.intel.com"
	<joonas.lahtinen@...ux.intel.com>, "Aaron, Ma" <aaron.ma@...onical.com>
Subject: RE: [PATCH 2/2] drm/i915/backlight: Add get brightness support of
 DPCD via AUX

> Subject: [PATCH 2/2] drm/i915/backlight: Add get brightness support of DPCD
> via AUX
> 
> Use drm common helper to read brightness from both luminance and AUX
> mode to support get_brightness from DPCD via AUX.
> 
> Signed-off-by: Aaron Ma <aaron.ma@...onical.com>
> ---
>  .../drm/i915/display/intel_dp_aux_backlight.c | 20 ++++++-------------
>  1 file changed, 6 insertions(+), 14 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 0a3a3f6a5f9d8..0ee6fd0f41ef0 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
> @@ -454,24 +454,16 @@ static u32 intel_dp_aux_vesa_get_backlight(struct
> intel_connector *connector, en  {
>  	struct intel_dp *intel_dp = enc_to_intel_dp(connector->encoder);
>  	struct intel_panel *panel = &connector->panel;
> -	u8 buf[3];
> -	u32 val = 0;
> -	int ret;
> 
> -	if (panel->backlight.edp.vesa.luminance_control_support) {
> -		ret = drm_dp_dpcd_read(&intel_dp->aux,
> DP_EDP_PANEL_TARGET_LUMINANCE_VALUE, buf,
> -				       sizeof(buf));
> -		if (ret < 0) {
> -			drm_err(intel_dp->aux.drm_dev,
> -				"[CONNECTOR:%d:%s] Failed to read
> Luminance from DPCD\n",
> -				connector->base.base.id, connector-
> >base.name);
> -			return 0;
> -		}
> +	if (!panel->backlight.edp.vesa.info.aux_set) {
> +		u32 pwm_level = panel->backlight.pwm_funcs->get(connector,
> unused);
> 
> -		val |= buf[0] | buf[1] << 8 | buf[2] << 16;
> -		return val / 1000;
> +		return intel_backlight_level_from_pwm(connector,
> pwm_level);
>  	}
> 
> +	connector->panel.backlight.level =
> +		drm_edp_backlight_get_level(&intel_dp->aux,
> +&panel->backlight.edp.vesa.info);
> +

Just call the intel_dp_aux_vesa_get_backlight here and call the drm_edp_backlight get level in there

Regards,
Suraj Kandpal


>  	return connector->panel.backlight.level;  }
> 
> --
> 2.43.0