linux-kernel - Re: [PATCH v3 30/37] drm/bridge: Assume that a bridge is atomic if it has atomic

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Message-ID: <vjdpctck2afcjrt2rlgjtzmrkf4a5bg5ihymc53vuw6md576wd@kbb5y27a5woi>
Date: Thu, 13 Feb 2025 18:29:46 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Maxime Ripard <mripard@...nel.org>
Cc: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
	Thomas Zimmermann <tzimmermann@...e.de>, David Airlie <airlied@...il.com>, 
	Simona Vetter <simona@...ll.ch>, 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>, Douglas Anderson <dianders@...omium.org>, 
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 30/37] drm/bridge: Assume that a bridge is atomic if
 it has atomic_reset

On Thu, Feb 13, 2025 at 03:43:49PM +0100, Maxime Ripard wrote:
> The drm_atomic_bridge_check() runs the atomic_check callback if needed,
> or falls back to mode_fixup if it's not there.
> 
> Going forward, we'll need to setup the bridge atomic state even though
> drivers might not be implementing atomic_check at all.
> 
> We can thus switch to using drm_bridge_is_atomic() to take the atomic
> path, and do additional things there in the future, or go the mode_fixup
> route.

This will break bridges like tc358768, rcar_lvds and mtk_hdmi: they
implement atomic_reset() and mode_fixup().

> 
> Signed-off-by: Maxime Ripard <mripard@...nel.org>
> ---
>  drivers/gpu/drm/drm_bridge.c | 12 +++++++-----
>  1 file changed, 7 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
> index d2525d0b1324cc3a63e32f5bf6ca6c4f9034eb4e..b6d24092674c8fa33d9b6ebab9ece0f91fb8f8ea 100644
> --- a/drivers/gpu/drm/drm_bridge.c
> +++ b/drivers/gpu/drm/drm_bridge.c
> @@ -803,23 +803,25 @@ EXPORT_SYMBOL(drm_atomic_bridge_chain_enable);
>  
>  static int drm_atomic_bridge_check(struct drm_bridge *bridge,
>  				   struct drm_crtc_state *crtc_state,
>  				   struct drm_connector_state *conn_state)
>  {
> -	if (bridge->funcs->atomic_check) {
> +	if (drm_bridge_is_atomic(bridge)) {
>  		struct drm_bridge_state *bridge_state;
>  		int ret;
>  
>  		bridge_state = drm_atomic_get_new_bridge_state(crtc_state->state,
>  							       bridge);
>  		if (WARN_ON(!bridge_state))
>  			return -EINVAL;
>  
> -		ret = bridge->funcs->atomic_check(bridge, bridge_state,
> -						  crtc_state, conn_state);
> -		if (ret)
> -			return ret;
> +		if (bridge->funcs->atomic_check) {
> +			ret = bridge->funcs->atomic_check(bridge, bridge_state,
> +							  crtc_state, conn_state);
> +			if (ret)
> +				return ret;
> +		}
>  	} else if (bridge->funcs->mode_fixup) {
>  		if (!bridge->funcs->mode_fixup(bridge, &crtc_state->mode,
>  					       &crtc_state->adjusted_mode))
>  			return -EINVAL;
>  	}
> 
> -- 
> 2.48.0
> 

-- 
With best wishes
Dmitry