linux-kernel - Re: [PATCH v7 21/36] drm/connector: hdmi: Add Broadcast RGB property

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Message-ID: <20240223112837.7c0394d7.pekka.paalanen@collabora.com>
Date: Fri, 23 Feb 2024 11:28:37 +0200
From: Pekka Paalanen <pekka.paalanen@...labora.com>
To: Maxime Ripard <mripard@...nel.org>
Cc: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Thomas Zimmermann
 <tzimmermann@...e.de>, David Airlie <airlied@...il.com>, Daniel Vetter
 <daniel@...ll.ch>, Jonathan Corbet <corbet@....net>, Sandy Huang
 <hjc@...k-chips.com>, Heiko Stübner <heiko@...ech.de>,
 Chen-Yu Tsai <wens@...e.org>, Jernej Skrabec <jernej.skrabec@...il.com>,
 Samuel Holland <samuel@...lland.org>, Hans Verkuil <hverkuil@...all.nl>,
 Sebastian Wick <sebastian.wick@...hat.com>, Ville Syrjälä
 <ville.syrjala@...ux.intel.com>, dri-devel@...ts.freedesktop.org,
 linux-arm-kernel@...ts.infradead.org, linux-doc@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
 linux-rockchip@...ts.infradead.org, linux-sunxi@...ts.linux.dev, Dave
 Stevenson <dave.stevenson@...pberrypi.com>
Subject: Re: [PATCH v7 21/36] drm/connector: hdmi: Add Broadcast RGB
 property

On Thu, 22 Feb 2024 19:14:07 +0100
Maxime Ripard <mripard@...nel.org> wrote:

> The i915 driver has a property to force the RGB range of an HDMI output.
> The vc4 driver then implemented the same property with the same
> semantics. KWin has support for it, and a PR for mutter is also there to
> support it.
> 
> Both drivers implementing the same property with the same semantics,
> plus the userspace having support for it, is proof enough that it's
> pretty much a de-facto standard now and we can provide helpers for it.
> 
> Let's plumb it into the newly created HDMI connector.
> 
> Reviewed-by: Dave Stevenson <dave.stevenson@...pberrypi.com>
> Signed-off-by: Maxime Ripard <mripard@...nel.org>
> ---
>  Documentation/gpu/kms-properties.csv      |  1 -
>  drivers/gpu/drm/drm_atomic.c              |  2 +
>  drivers/gpu/drm/drm_atomic_state_helper.c |  4 +-
>  drivers/gpu/drm/drm_atomic_uapi.c         |  4 ++
>  drivers/gpu/drm/drm_connector.c           | 89 +++++++++++++++++++++++++++++++
>  include/drm/drm_connector.h               | 36 +++++++++++++
>  6 files changed, 134 insertions(+), 2 deletions(-)

..

> diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
> index 591d2d500f61..6ffe59d01698 100644
> --- a/drivers/gpu/drm/drm_connector.c
> +++ b/drivers/gpu/drm/drm_connector.c
> @@ -1212,6 +1212,29 @@ static const u32 dp_colorspaces =
>  	BIT(DRM_MODE_COLORIMETRY_BT2020_CYCC) |
>  	BIT(DRM_MODE_COLORIMETRY_BT2020_YCC);
>  
> +static const struct drm_prop_enum_list broadcast_rgb_names[] = {
> +	{ DRM_HDMI_BROADCAST_RGB_AUTO, "Automatic" },
> +	{ DRM_HDMI_BROADCAST_RGB_FULL, "Full" },
> +	{ DRM_HDMI_BROADCAST_RGB_LIMITED, "Limited 16:235" },
> +};
> +
> +/*
> + * drm_hdmi_connector_get_broadcast_rgb_name - Return a string for HDMI connector RGB broadcast selection
> + * @broadcast_rgb: Broadcast RGB selection to compute name of
> + *
> + * Returns: the name of the Broadcast RGB selection, or NULL if the type
> + * is not valid.
> + */
> +const char *
> +drm_hdmi_connector_get_broadcast_rgb_name(enum drm_hdmi_broadcast_rgb broadcast_rgb)
> +{
> +	if (broadcast_rgb > DRM_HDMI_BROADCAST_RGB_LIMITED)
> +		return NULL;
> +
> +	return broadcast_rgb_names[broadcast_rgb].name;
> +}
> +EXPORT_SYMBOL(drm_hdmi_connector_get_broadcast_rgb_name);
> +
>  static const char * const output_format_str[] = {
>  	[HDMI_COLORSPACE_RGB]		= "RGB",
>  	[HDMI_COLORSPACE_YUV420]	= "YUV 4:2:0",
> @@ -1708,6 +1731,39 @@ EXPORT_SYMBOL(drm_connector_attach_dp_subconnector_property);
>  /**
>   * DOC: HDMI connector properties
>   *
> + * Broadcast RGB (HDMI specific)
> + *      Indicates the Quantization Range (Full vs Limited) used. The color
> + *      processing pipeline will be adjusted to match the value of the
> + *      property, and the Infoframes will be generated and sent accordingly.
> + *
> + *      This property is only relevant if the HDMI output format is RGB. If
> + *      it's one of the YCbCr variant, it will be ignored and the output will
> + *      use a limited quantization range.
> + *
> + *      The CRTC attached to the connector must be configured by user-space to
> + *      always produce full-range pixels.
> + *
> + *      The value of this property can be one of the following:
> + *
> + *      Automatic:
> + *              The quantization range is selected automatically based on the
> + *              mode according to the HDMI specifications (HDMI 1.4b - Section
> + *              6.6 - Video Quantization Ranges).
> + *
> + *      Full:
> + *              Full quantization range is forced.
> + *
> + *      Limited 16:235:
> + *              Limited quantization range is forced. Unlike the name suggests,
> + *              this works for any number of bits-per-component.
> + *
> + *      Property values other than Automatic can result in colors being off (if
> + *      limited is selected but the display expects full), or a black screen
> + *      (if full is selected but the display expects limited).
> + *
> + *      Drivers can set up this property by calling
> + *      drm_connector_attach_broadcast_rgb_property().
> + *
>   * content type (HDMI specific):
>   *	Indicates content type setting to be used in HDMI infoframes to indicate
>   *	content type for the external device, so that it adjusts its display

This piece of doc looks good to me, so

Acked-by: Pekka Paalanen <pekka.paalanen@...labora.com>


Thanks,
pq

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