RE: drm/i915/backlight: Remove DP_EDP_BACKLIGHT_AUX_ENABLE_CAP check for DPCD backlight

> Subject: Re: drm/i915/backlight: Remove
> DP_EDP_BACKLIGHT_AUX_ENABLE_CAP check for DPCD backlight
> 
> On Thu, 16 Jul 2026, Suraj Kandpal wrote:
> > Turns out Some panels allow only backlight AUX based backlight
> 
> nits:
> s/Some/some/
> s/backlight AUX/AUX/
> 
> > by just setting the DP_EDP_BACKLIGHT_BRIGHTNESS_AUX_SET_CAP and not
> > setting the DP_EDP_BACKLIGHT_AUX_ENABLE_CAP.
> > If we make DP_EDP_BACKLIGHT_AUX_ENABLE_CAP a necessity for AUX based
> > DPCD backlight these panels loose the ability to manipulate backlight
> > via AUX, specially ones with no PWM controller.
> 
> maybe: s/specially/especially/
> 
> > Remove this check from function so that panels who do not advertise
> > DP_EDP_BACKLIGHT_AUX_ENABLE_CAP but advertise
> > DP_EDP_BACKLIGHT_BRIGHTNESS_AUX_SET_CAP are able to manipulate
> > backlight again.
> >
> > Fixes: ed8be780bdbc ("drm/i915/backlight: Fix VESA backlight possible
> > check condition")
> > Closes:
> > https://gitlab.freedesktop.org/drm/i915/kernel/-/work_items/16507
> > Signed-off-by: Suraj Kandpal <[email protected]>
> 
> > ---
> > drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c | 3 +--
> > 1 file changed, 1 insertion(+), 2 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 7a6c07f6aaeb..83245cb738e5 100644
> > --- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
> > +++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
> > @@ -619,8 +619,7 @@ check_if_vesa_backlight_possible(struct intel_dp
> *intel_dp)
> > 	 * Since we only support Fully AUX Based VESA Backlight interface make
> sure
> > 	 * backlight enable is possible via AUX along with backlight adjustment
> > 	 */
> 
> Wondering if the comment above needs any adjustment?

You are right this comment will need to be removed  now

> 
> Either way:
> Reviewed-by: Michał Grzelak <[email protected]>
> 

Thanks for the reviews,
Pushed to din with above mentioned changes

Regards,
Suraj Kandpal

> BR,
> Michał
> 
> > -	if (!(intel_dp->edp_dpcd[1] & DP_EDP_BACKLIGHT_AUX_ENABLE_CAP
> &&
> > -	      intel_dp->edp_dpcd[2] &
> DP_EDP_BACKLIGHT_BRIGHTNESS_AUX_SET_CAP))
> > +	if (!(intel_dp->edp_dpcd[2] &
> > +DP_EDP_BACKLIGHT_BRIGHTNESS_AUX_SET_CAP))
> > 		return false;
> >
> > 	ret = drm_dp_dpcd_read_byte(&intel_dp->aux,
> > DP_EDP_PWMGEN_BIT_COUNT_CAP_MIN, &bit_min);
> >