[PATCH 5/7] drm/i915/backlight: Add function to change brightness in NITS for VESA

[Jani Nikula]

On Fri, 24 Jan 2025, Suraj Kandpal <suraj.kandpal at intel.com> wrote:
> Create a function that fills in the value for
> PANEL_TARGET_LUMINANCE_VALUE which helps in changing the brightness in
> NITS using VESA interface.
>
> Signed-off-by: Suraj Kandpal <suraj.kandpal at intel.com>
> ---
>  .../drm/i915/display/intel_dp_aux_backlight.c | 29 +++++++++++++++++++
>  1 file changed, 29 insertions(+)
>
> 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 ac9a69fe3f10..d794397656dd 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
> @@ -474,6 +474,30 @@ static u32 intel_dp_aux_vesa_get_backlight(struct intel_connector *connector, en
>  	return connector->panel.backlight.level;
>  }
>  
> +static int
> +intel_dp_aux_vesa_set_nits_brightness(struct intel_connector *connector, u32 level)

_set_luminance()?

Troughout the series, I'd prefer "luminance" over "nits", i.e. measure
over unit.

> +{
> +	struct intel_dp *intel_dp = enc_to_intel_dp(connector->encoder);
> +	u8 buf[3];
> +	int ret;
> +
> +	level = level * 1000;
> +	level &= 0xffffff;
> +	buf[0] = (level & 0x0000ff);
> +	buf[1] = (level & 0x00ff00) >> 8;
> +	buf[2] = (level & 0xff0000) >> 16;
> +
> +	ret = drm_dp_dpcd_write(&intel_dp->aux, DP_EDP_PANEL_TARGET_LUMINANCE_VALUE, buf, sizeof(buf));
> +	if (ret != sizeof(buf)) {
> +		drm_err(intel_dp->aux.drm_dev,
> +			"%s: Failed to VESA AUX Nits backlight level: %d\n",
> +			intel_dp->aux.name, ret);
> +		return -EINVAL;
> +	} else {
> +		return 0;
> +	}
> +}
> +
>  static void
>  intel_dp_aux_vesa_set_backlight(const struct drm_connector_state *conn_state, u32 level)
>  {
> @@ -481,6 +505,11 @@ intel_dp_aux_vesa_set_backlight(const struct drm_connector_state *conn_state, u3
>  	struct intel_panel *panel = &connector->panel;
>  	struct intel_dp *intel_dp = enc_to_intel_dp(connector->encoder);
>  
> +	if (panel->backlight.edp.vesa.nits_support) {
> +		if (!intel_dp_aux_vesa_set_nits_brightness(connector, level))
> +			return;
> +	}
> +
>  	if (!panel->backlight.edp.vesa.info.aux_set) {
>  		const u32 pwm_level = intel_backlight_level_to_pwm(connector, level);

-- 
Jani Nikula, Intel