linux-kernel - Re: [PATCH v2] drm/bridge-connector: Prioritize supported_formats over ycbcr_420

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Message-ID: <dn625hkcujqlre74wu3hezlcbkxza5urydgcl3kvs3exbr4tl7@rpznp2zefpoe>
Date: Tue, 17 Dec 2024 01:32:16 +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 v2] drm/bridge-connector: Prioritize supported_formats
 over ycbcr_420_allowed

On Tue, Dec 17, 2024 at 01:17:48AM +0200, Cristian Ciocaltea wrote:
> Hi Dmitry,
> 
> On 12/10/24 3:12 AM, Dmitry Baryshkov wrote:
> > On Fri, Dec 06, 2024 at 10:00:46PM +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.
> > 
> > I think this should be handled in a different way: during HDMI connector
> > init verify that HDMI_COLORSPACE_YUV420 matches the
> > drm_connector->ycbcr_420_allowed value and rejects incompatible
> > connectors.
> 
> I added a 2nd patch in v3 [1] to perform this verification on HDMI
> connector init, but I think we still need a proper handling of the
> inconsistency at bridge[-connector] level. I simplified a bit the initial
> approach, hopefully that would bring us closer to an acceptable solution.

I'm sorry, I first commented on the new patchseries. I think that the
second patch is enough.

> 
> Thanks,
> Cristian
> 
> [1] https://lore.kernel.org/lkml/20241217-bridge-conn-fmt-prio-v3-0-3ecb3c8fc06f@collabora.com/

-- 
With best wishes
Dmitry