linux-kernel - Re: [PATCH v3 1/2] drm/bridge-connector: Prioritize supported_formats over ycbcr_420

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Message-ID: <c36o6ro5qqfkqipltlecb3r22d5k3xiqdt46rtl2gdyha7xtmm@l2ovdfono7np>
Date: Tue, 17 Dec 2024 01:27:49 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Cristian Ciocaltea <cristian.ciocaltea@...labora.com>
Cc: Andrzej Hajda <andrzej.hajda@...el.com>, 
	Neil Armstrong <neil.armstrong@...aro.org>, Robert Foss <rfoss@...nel.org>, 
	Laurent Pinchart <Laurent.pinchart@...asonboard.com>, Jonas Karlman <jonas@...boo.se>, 
	Jernej Skrabec <jernej.skrabec@...il.com>, Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
	Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, 
	David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, kernel@...labora.com, 
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/2] drm/bridge-connector: Prioritize
 supported_formats over ycbcr_420_allowed

On Tue, Dec 17, 2024 at 12:54:07AM +0200, Cristian Ciocaltea wrote:
> Bridges having the DRM_BRIDGE_OP_HDMI flag set in drm_bridge->ops are
> supposed to rely on drm_bridge->supported_formats bitmask to advertise
> the supported colorspaces, including HDMI_COLORSPACE_YUV420.  Therefore,
> the newly introduced drm_bridge->ycbcr_420_allowed flag becomes
> redundant in this particular context.
> 
> Moreover, when drm_bridge_connector gets initialised, only
> drm_bridge->ycbcr_420_allowed is considered in the process of adjusting
> the equivalent property of the base drm_connector, which effectively
> discards the formats advertised by the HDMI bridge.
> 
> Handle the inconsistency by overwriting drm_bridge->ycbcr_420_allowed
> for HDMI bridges according to drm_bridge->supported_formats, before
> adding them to the global bridge list.
> 
> Additionally, ensure the YUV420 related bit is removed from the bitmask
> passed to drmm_connector_hdmi_init() when the final ycbcr_420_allowed
> flag for the connector ends up not being set (i.e. the case of having at
> least one non-HDMI bridge in the pipeline that didn't enable it).
> 
> Fixes: 3ced1c687512 ("drm/display: bridge_connector: handle ycbcr_420_allowed")
> Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@...labora.com>
> ---
>  drivers/gpu/drm/display/drm_bridge_connector.c | 8 ++++++--
>  drivers/gpu/drm/drm_bridge.c                   | 4 ++++
>  2 files changed, 10 insertions(+), 2 deletions(-)

I think the second patch in the series is enough, it ensures that
connector's state is consistent, no matter if the drm_bridge_connector
is being used or a normal drm_connector.

Nevertheless, I'd leave the final decision to DRM maintainers.

-- 
With best wishes
Dmitry