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

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Message-ID: <CAJ6xRxU1B0wh9eNO8x62+HH_SS_H-eR-Sco9cAeH9fKrTQ+kMw@mail.gmail.com>
Date: Fri, 26 Sep 2025 17:52:30 +0800
From: Aaron Ma <aaron.ma@...onical.com>
To: "Kandpal, Suraj" <suraj.kandpal@...el.com>
Cc: "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>, 
	"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>
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@...el.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@...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
>

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
>