linux-kernel - Re: [PATCH v4 1/4] drm/bridge: Prioritize supported_formats over ycbcr_420

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Message-ID: <fxejrxzouuwioyfu5hcrpsy5mabmjknxvtozefrkx4fnb2phog@ncc2wrli7uks>
Date: Tue, 24 Dec 2024 21:08:27 +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 v4 1/4] drm/bridge: Prioritize supported_formats over
 ycbcr_420_allowed

On Tue, Dec 24, 2024 at 08:22:41PM +0200, Cristian Ciocaltea wrote:
> Bridges having DRM_BRIDGE_OP_HDMI set in their ->ops are supposed to
> rely on the ->supported_formats bitmask to advertise the permitted
> colorspaces, including HDMI_COLORSPACE_YUV420.
> 
> However, a new flag ->ycbcr_420_allowed has been recently introduced,
> which brings the necessity to require redundant and potentially
> inconsistent information to be provided on HDMI bridges initialization.
> 
> Adjust ->ycbcr_420_allowed for HDMI bridges according to
> ->supported_formats, right before adding them to the global bridge list.
> This keeps the initialization process straightforward and unambiguous,
> thereby preventing any further confusion.
> 
> Fixes: 3ced1c687512 ("drm/display: bridge_connector: handle ycbcr_420_allowed")
> Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@...labora.com>
> ---
>  drivers/gpu/drm/drm_bridge.c | 4 ++++
>  1 file changed, 4 insertions(+)

I'm still slightly torn between this patch and a simple
drm_WARN_ON(bridge->dev, bridge->ycbcr_420_allowed !=
(bridge->supported_formats & BIT(HDMI_COLORSPACE_YUV420)))

Nevertheless,

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>

> 
> diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
> index c6af46dd02bfa9e15b59e4c460debdd7fd84be44..241a384ebce39b4a3db58c208af27960904fc662 100644
> --- a/drivers/gpu/drm/drm_bridge.c
> +++ b/drivers/gpu/drm/drm_bridge.c
> @@ -207,6 +207,10 @@ void drm_bridge_add(struct drm_bridge *bridge)
>  {
>  	mutex_init(&bridge->hpd_mutex);
>  
> +	if (bridge->ops & DRM_BRIDGE_OP_HDMI)
> +		bridge->ycbcr_420_allowed = !!(bridge->supported_formats &
> +					       BIT(HDMI_COLORSPACE_YUV420));
> +
>  	mutex_lock(&bridge_lock);
>  	list_add_tail(&bridge->list, &bridge_list);
>  	mutex_unlock(&bridge_lock);
> 
> -- 
> 2.47.0
> 

-- 
With best wishes
Dmitry