On Fri, Sep 26, 2025 at 5:23 PM Kandpal, Suraj <[email protected]> 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 <[email protected]>
> > ---
> > 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
>
