linux-kernel - Re: [PATCH v8 16/27] drm/connector: hdmi: Add Broadcast RGB property

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Message-ID: <20240308172623.37663eb6.pekka.paalanen@collabora.com>
Date: Fri, 8 Mar 2024 17:26:23 +0200
From: Pekka Paalanen <pekka.paalanen@...labora.com>
To: Alexander Stein <alexander.stein@...tq-group.com>
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>, dri-devel@...ts.freedesktop.org, Hans
 Verkuil <hverkuil@...all.nl>, Sebastian Wick <sebastian.wick@...hat.com>,
 Ville Syrjälä <ville.syrjala@...ux.intel.com>,
 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, Maxime
 Ripard <mripard@...nel.org>, Dave Stevenson
 <dave.stevenson@...pberrypi.com>
Subject: Re: [PATCH v8 16/27] drm/connector: hdmi: Add Broadcast RGB
 property

On Fri, 08 Mar 2024 12:26:14 +0100
Alexander Stein <alexander.stein@...tq-group.com> wrote:

> Hi Maxime,
> 
> Am Donnerstag, 7. März 2024, 14:38:43 CET schrieb Maxime Ripard:
> > 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>
> > Acked-by: Pekka Paalanen <pekka.paalanen@...labora.com>
> > Reviewed-by: Sebastian Wick <sebastian.wick@...hat.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           | 88 +++++++++++++++++++++++++++++++
> >  include/drm/drm_connector.h               | 36 +++++++++++++
> >  6 files changed, 133 insertions(+), 2 deletions(-)

..

> > diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
> > index 591d2d500f61..0272e1d05cc6 100644
> > --- a/drivers/gpu/drm/drm_connector.c
> > +++ b/drivers/gpu/drm/drm_connector.c
> > @@ -1210,10 +1210,33 @@ static const u32 dp_colorspaces =
> >  	BIT(DRM_MODE_COLORIMETRY_SYCC_601) |
> >  	BIT(DRM_MODE_COLORIMETRY_OPYCC_601) |
> >  	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)  
> 
> I don't know if this was brought up before. IMHO it's easier to read checking:
>  if (broadcast_rgb > ARRAY_SIZE(broadcast_rgb_names)

You have an off-by-one bug in that suggestion. ;-)


Thanks,
pq

> 
> Best regards,
> Alexander
> 
> > +		return NULL;
> > +
> > +	return broadcast_rgb_names[broadcast_rgb].name;
> > +}
> > +EXPORT_SYMBOL(drm_hdmi_connector_get_broadcast_rgb_name);

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