[PATCH 1/2] drm/dp: Add drm_edp_backlight_get_level

[PATCH 1/2] drm/dp: Add drm_edp_backlight_get_level

[Aaron Ma]

Implement drm_edp_backlight_get_level() to read the current
backlight brightness level from eDP DPCD registers via AUX channel.

Signed-off-by: Aaron Ma <aaron.ma@canonical.com>
---
 drivers/gpu/drm/display/drm_dp_helper.c | 52 +++++++++++++++++++++++++
 include/drm/display/drm_dp_helper.h     |  1 +
 2 files changed, 53 insertions(+)

diff --git a/drivers/gpu/drm/display/drm_dp_helper.c b/drivers/gpu/drm/display/drm_dp_helper.c
index 1ecc3df7e3167..0cfb357ebd9e2 100644
--- a/drivers/gpu/drm/display/drm_dp_helper.c
+++ b/drivers/gpu/drm/display/drm_dp_helper.c
@@ -3945,6 +3945,58 @@ int drm_dp_pcon_convert_rgb_to_ycbcr(struct drm_dp_aux *aux, u8 color_spc)
 }
 EXPORT_SYMBOL(drm_dp_pcon_convert_rgb_to_ycbcr);
 
+/**
+ * drm_edp_backlight_get_level - Get the backlight level of eDP DPCD via AUX
+ * @aux: The DP aux device
+ * @bl: Backlight capability info from the panel
+ *
+ * Reads the current backlight brightness level from luminance mode
+ * (24-bit value in nits) or DPCD AUX mode(16-bit and 8-bit modes).
+ *
+ * Returns: Current backlight level.
+ */
+u32 drm_edp_backlight_get_level(struct drm_dp_aux *aux, const struct drm_edp_backlight_info *bl)
+{
+	int ret;
+	u8 buf[3] = { 0 };
+	u32 level = 0;
+
+	if (!(bl->aux_set || bl->luminance_set))
+		return 0;
+
+	if (bl->luminance_set) {
+		ret = drm_dp_dpcd_read(aux, DP_EDP_PANEL_TARGET_LUMINANCE_VALUE, buf, sizeof(buf));
+		if (ret < 0) {
+			DRM_DEV_ERROR(aux->drm_dev->dev,
+				      "%s: Failed to read luminance value: %d\n",
+				      aux->name, ret);
+			return 0;
+		}
+		level = (buf[2] << 16 | buf[1] << 8 | buf[0]) / 1000;
+	} else if (bl->lsb_reg_used) {
+		ret = drm_dp_dpcd_read(aux, DP_EDP_BACKLIGHT_BRIGHTNESS_MSB, buf, 2);
+		if (ret < 0) {
+			DRM_DEV_ERROR(aux->drm_dev->dev,
+				      "%s: Failed to read backlight level: %d\n",
+				      aux->name, ret);
+			return 0;
+		}
+		level = buf[0] << 8 | buf[1];
+	} else {
+		ret = drm_dp_dpcd_read(aux, DP_EDP_BACKLIGHT_BRIGHTNESS_MSB, buf, 1);
+		if (ret < 0) {
+			DRM_DEV_ERROR(aux->drm_dev->dev,
+				      "%s: Failed to read backlight level: %d\n",
+				      aux->name, ret);
+			return 0;
+		}
+		level = buf[0];
+	}
+
+	return level;
+}
+EXPORT_SYMBOL(drm_edp_backlight_get_level);
+
 /**
  * drm_edp_backlight_set_level() - Set the backlight level of an eDP panel via AUX
  * @aux: The DP AUX channel to use
diff --git a/include/drm/display/drm_dp_helper.h b/include/drm/display/drm_dp_helper.h
index 87caa4f1fdb86..0b045a47ae573 100644
--- a/include/drm/display/drm_dp_helper.h
+++ b/include/drm/display/drm_dp_helper.h
@@ -864,6 +864,7 @@ drm_edp_backlight_init(struct drm_dp_aux *aux, struct drm_edp_backlight_info *bl
 		       u32 max_luminance,
 		       u16 driver_pwm_freq_hz, const u8 edp_dpcd[EDP_DISPLAY_CTL_CAP_SIZE],
 		       u32 *current_level, u8 *current_mode, bool need_luminance);
+u32 drm_edp_backlight_get_level(struct drm_dp_aux *aux, const struct drm_edp_backlight_info *bl);
 int drm_edp_backlight_set_level(struct drm_dp_aux *aux, const struct drm_edp_backlight_info *bl,
 				u32 level);
 int drm_edp_backlight_enable(struct drm_dp_aux *aux, const struct drm_edp_backlight_info *bl,
-- 
2.43.0

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

[Aaron Ma]

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@canonical.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);
+
 	return connector->panel.backlight.level;
 }
 
-- 
2.43.0

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

[Kandpal, Suraj]

> 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@canonical.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

Re: [PATCH 2/2] drm/i915/backlight: Add get brightness support of DPCD via AUX

[Aaron Ma]

On Fri, Sep 26, 2025 at 5:26 PM Kandpal, Suraj <suraj.kandpal@intel.com> wrote:
>
> > 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@canonical.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
>

Do you mean no call of  pwm get?

I thought it should be aligned with set_level when aux_set == 0.

Thanks,
Aaron

> Regards,
> Suraj Kandpal
>
>
> >       return connector->panel.backlight.level;  }
> >
> > --
> > 2.43.0
>

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

[Kandpal, Suraj]

> -----Original Message-----
> From: Aaron Ma <aaron.ma@canonical.com>
> Sent: Friday, September 26, 2025 3:23 PM
> To: Kandpal, Suraj <suraj.kandpal@intel.com>
> Cc: dri-devel@lists.freedesktop.org; intel-gfx@lists.freedesktop.org; linux-
> kernel@vger.kernel.org; maarten.lankhorst@linux.intel.com;
> mripard@kernel.org; tzimmermann@suse.de; airlied@gmail.com;
> simona@ffwll.ch; jani.nikula@linux.intel.com; Vivi, Rodrigo
> <rodrigo.vivi@intel.com>; Deak, Imre <imre.deak@intel.com>;
> joonas.lahtinen@linux.intel.com
> Subject: Re: [PATCH 2/2] drm/i915/backlight: Add get brightness support of
> DPCD via AUX
> 
> On Fri, Sep 26, 2025 at 5:26 PM Kandpal, Suraj <suraj.kandpal@intel.com>
> wrote:
> >
> > > 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@canonical.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
> >
> 
> Do you mean no call of  pwm get?
> 
> I thought it should be aligned with set_level when aux_set == 0.

I misunderstood the code here its as it should be the diff just made it seem weird

Regards,
Suraj Kandpal

> 
> Thanks,
> Aaron
> 
> > Regards,
> > Suraj Kandpal
> >
> >
> > >       return connector->panel.backlight.level;  }
> > >
> > > --
> > > 2.43.0
> >

RE: [PATCH 1/2] drm/dp: Add drm_edp_backlight_get_level

[Kandpal, Suraj]

> Subject: [PATCH 1/2] drm/dp: Add drm_edp_backlight_get_level
> 
> Implement drm_edp_backlight_get_level() to read the current backlight
> brightness level from eDP DPCD registers via AUX channel.
> 
> Signed-off-by: Aaron Ma <aaron.ma@canonical.com>
> ---
>  drivers/gpu/drm/display/drm_dp_helper.c | 52 +++++++++++++++++++++++++
>  include/drm/display/drm_dp_helper.h     |  1 +
>  2 files changed, 53 insertions(+)
> 
> diff --git a/drivers/gpu/drm/display/drm_dp_helper.c
> b/drivers/gpu/drm/display/drm_dp_helper.c
> index 1ecc3df7e3167..0cfb357ebd9e2 100644
> --- a/drivers/gpu/drm/display/drm_dp_helper.c
> +++ b/drivers/gpu/drm/display/drm_dp_helper.c
> @@ -3945,6 +3945,58 @@ int drm_dp_pcon_convert_rgb_to_ycbcr(struct
> drm_dp_aux *aux, u8 color_spc)  }
> EXPORT_SYMBOL(drm_dp_pcon_convert_rgb_to_ycbcr);
> 
> +/**
> + * drm_edp_backlight_get_level - Get the backlight level of eDP DPCD
> +via AUX
> + * @aux: The DP aux device
> + * @bl: Backlight capability info from the panel
> + *
> + * Reads the current backlight brightness level from luminance mode
> + * (24-bit value in nits) or DPCD AUX mode(16-bit and 8-bit modes).
> + *
> + * Returns: Current backlight level.
> + */
> +u32 drm_edp_backlight_get_level(struct drm_dp_aux *aux, const struct
> +drm_edp_backlight_info *bl) {
> +	int ret;
> +	u8 buf[3] = { 0 };
> +	u32 level = 0;
> +
> +	if (!(bl->aux_set || bl->luminance_set))
> +		return 0;
> +
> +	if (bl->luminance_set) {
> +		ret = drm_dp_dpcd_read(aux,
> DP_EDP_PANEL_TARGET_LUMINANCE_VALUE, buf, sizeof(buf));
> +		if (ret < 0) {
> +			DRM_DEV_ERROR(aux->drm_dev->dev,
> +				      "%s: Failed to read luminance value: %d\n",
> +				      aux->name, ret);
> +			return 0;
> +		}
> +		level = (buf[2] << 16 | buf[1] << 8 | buf[0]) / 1000;
> +	} else if (bl->lsb_reg_used) {
> +		ret = drm_dp_dpcd_read(aux,
> DP_EDP_BACKLIGHT_BRIGHTNESS_MSB, buf, 2);
> +		if (ret < 0) {
> +			DRM_DEV_ERROR(aux->drm_dev->dev,

Use drm_err here ditto for same where ever this has been used

Regards,
Suraj Kandpal

> +				      "%s: Failed to read backlight level: %d\n",
> +				      aux->name, ret);
> +			return 0;
> +		}
> +		level = buf[0] << 8 | buf[1];
> +	} else {
> +		ret = drm_dp_dpcd_read(aux,
> DP_EDP_BACKLIGHT_BRIGHTNESS_MSB, buf, 1);
> +		if (ret < 0) {
> +			DRM_DEV_ERROR(aux->drm_dev->dev,
> +				      "%s: Failed to read backlight level: %d\n",
> +				      aux->name, ret);
> +			return 0;
> +		}
> +		level = buf[0];
> +	}
> +
> +	return level;
> +}
> +EXPORT_SYMBOL(drm_edp_backlight_get_level);
> +
>  /**
>   * drm_edp_backlight_set_level() - Set the backlight level of an eDP panel via
> AUX
>   * @aux: The DP AUX channel to use
> diff --git a/include/drm/display/drm_dp_helper.h
> b/include/drm/display/drm_dp_helper.h
> index 87caa4f1fdb86..0b045a47ae573 100644
> --- a/include/drm/display/drm_dp_helper.h
> +++ b/include/drm/display/drm_dp_helper.h
> @@ -864,6 +864,7 @@ drm_edp_backlight_init(struct drm_dp_aux *aux,
> struct drm_edp_backlight_info *bl
>  		       u32 max_luminance,
>  		       u16 driver_pwm_freq_hz, const u8
> edp_dpcd[EDP_DISPLAY_CTL_CAP_SIZE],
>  		       u32 *current_level, u8 *current_mode, bool
> need_luminance);
> +u32 drm_edp_backlight_get_level(struct drm_dp_aux *aux, const struct
> +drm_edp_backlight_info *bl);
>  int drm_edp_backlight_set_level(struct drm_dp_aux *aux, const struct
> drm_edp_backlight_info *bl,
>  				u32 level);
>  int drm_edp_backlight_enable(struct drm_dp_aux *aux, const struct
> drm_edp_backlight_info *bl,
> --
> 2.43.0

Re: [PATCH 1/2] drm/dp: Add drm_edp_backlight_get_level

[Aaron Ma]

On Fri, Sep 26, 2025 at 5:23 PM Kandpal, Suraj <suraj.kandpal@intel.com> wrote:
>
> > Subject: [PATCH 1/2] drm/dp: Add drm_edp_backlight_get_level
> >
> > Implement drm_edp_backlight_get_level() to read the current backlight
> > brightness level from eDP DPCD registers via AUX channel.
> >
> > Signed-off-by: Aaron Ma <aaron.ma@canonical.com>
> > ---
> >  drivers/gpu/drm/display/drm_dp_helper.c | 52 +++++++++++++++++++++++++
> >  include/drm/display/drm_dp_helper.h     |  1 +
> >  2 files changed, 53 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/display/drm_dp_helper.c
> > b/drivers/gpu/drm/display/drm_dp_helper.c
> > index 1ecc3df7e3167..0cfb357ebd9e2 100644
> > --- a/drivers/gpu/drm/display/drm_dp_helper.c
> > +++ b/drivers/gpu/drm/display/drm_dp_helper.c
> > @@ -3945,6 +3945,58 @@ int drm_dp_pcon_convert_rgb_to_ycbcr(struct
> > drm_dp_aux *aux, u8 color_spc)  }
> > EXPORT_SYMBOL(drm_dp_pcon_convert_rgb_to_ycbcr);
> >
> > +/**
> > + * drm_edp_backlight_get_level - Get the backlight level of eDP DPCD
> > +via AUX
> > + * @aux: The DP aux device
> > + * @bl: Backlight capability info from the panel
> > + *
> > + * Reads the current backlight brightness level from luminance mode
> > + * (24-bit value in nits) or DPCD AUX mode(16-bit and 8-bit modes).
> > + *
> > + * Returns: Current backlight level.
> > + */
> > +u32 drm_edp_backlight_get_level(struct drm_dp_aux *aux, const struct
> > +drm_edp_backlight_info *bl) {
> > +     int ret;
> > +     u8 buf[3] = { 0 };
> > +     u32 level = 0;
> > +
> > +     if (!(bl->aux_set || bl->luminance_set))
> > +             return 0;
> > +
> > +     if (bl->luminance_set) {
> > +             ret = drm_dp_dpcd_read(aux,
> > DP_EDP_PANEL_TARGET_LUMINANCE_VALUE, buf, sizeof(buf));
> > +             if (ret < 0) {
> > +                     DRM_DEV_ERROR(aux->drm_dev->dev,
> > +                                   "%s: Failed to read luminance value: %d\n",
> > +                                   aux->name, ret);
> > +                     return 0;
> > +             }
> > +             level = (buf[2] << 16 | buf[1] << 8 | buf[0]) / 1000;
> > +     } else if (bl->lsb_reg_used) {
> > +             ret = drm_dp_dpcd_read(aux,
> > DP_EDP_BACKLIGHT_BRIGHTNESS_MSB, buf, 2);
> > +             if (ret < 0) {
> > +                     DRM_DEV_ERROR(aux->drm_dev->dev,
>
> Use drm_err here ditto for same where ever this has been used
>

I will send v2.
Thanks,
Aaron


> Regards,
> Suraj Kandpal
>
> > +                                   "%s: Failed to read backlight level: %d\n",
> > +                                   aux->name, ret);
> > +                     return 0;
> > +             }
> > +             level = buf[0] << 8 | buf[1];
> > +     } else {
> > +             ret = drm_dp_dpcd_read(aux,
> > DP_EDP_BACKLIGHT_BRIGHTNESS_MSB, buf, 1);
> > +             if (ret < 0) {
> > +                     DRM_DEV_ERROR(aux->drm_dev->dev,
> > +                                   "%s: Failed to read backlight level: %d\n",
> > +                                   aux->name, ret);
> > +                     return 0;
> > +             }
> > +             level = buf[0];
> > +     }
> > +
> > +     return level;
> > +}
> > +EXPORT_SYMBOL(drm_edp_backlight_get_level);
> > +
> >  /**
> >   * drm_edp_backlight_set_level() - Set the backlight level of an eDP panel via
> > AUX
> >   * @aux: The DP AUX channel to use
> > diff --git a/include/drm/display/drm_dp_helper.h
> > b/include/drm/display/drm_dp_helper.h
> > index 87caa4f1fdb86..0b045a47ae573 100644
> > --- a/include/drm/display/drm_dp_helper.h
> > +++ b/include/drm/display/drm_dp_helper.h
> > @@ -864,6 +864,7 @@ drm_edp_backlight_init(struct drm_dp_aux *aux,
> > struct drm_edp_backlight_info *bl
> >                      u32 max_luminance,
> >                      u16 driver_pwm_freq_hz, const u8
> > edp_dpcd[EDP_DISPLAY_CTL_CAP_SIZE],
> >                      u32 *current_level, u8 *current_mode, bool
> > need_luminance);
> > +u32 drm_edp_backlight_get_level(struct drm_dp_aux *aux, const struct
> > +drm_edp_backlight_info *bl);
> >  int drm_edp_backlight_set_level(struct drm_dp_aux *aux, const struct
> > drm_edp_backlight_info *bl,
> >                               u32 level);
> >  int drm_edp_backlight_enable(struct drm_dp_aux *aux, const struct
> > drm_edp_backlight_info *bl,
> > --
> > 2.43.0
>