linux-kernel - Re: [PATCH v8 3/5] drm/mxsfb: put the bridge returned by drm_bridge_chain_get_first

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Message-ID: <20250623160909.7d11cfee@booty>
Date: Mon, 23 Jun 2025 16:09:09 +0200
From: Luca Ceresoli <luca.ceresoli@...tlin.com>
To: Liu Ying <victor.liu@....com>
Cc: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Maxime Ripard
 <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, 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>, David Airlie
 <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, Marek Vasut
 <marex@...x.de>, Stefan Agner <stefan@...er.ch>, Shawn Guo
 <shawnguo@...nel.org>, Sascha Hauer <s.hauer@...gutronix.de>, Pengutronix
 Kernel Team <kernel@...gutronix.de>, Fabio Estevam <festevam@...il.com>,
 Hui Pu <Hui.Pu@...ealthcare.com>, Thomas Petazzoni
 <thomas.petazzoni@...tlin.com>, dri-devel@...ts.freedesktop.org,
 linux-kernel@...r.kernel.org, imx@...ts.linux.dev,
 linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v8 3/5] drm/mxsfb: put the bridge returned by
 drm_bridge_chain_get_first_bridge()

On Mon, 23 Jun 2025 11:06:37 +0800
Liu Ying <victor.liu@....com> wrote:

[...]

> > diff --git a/drivers/gpu/drm/mxsfb/lcdif_kms.c b/drivers/gpu/drm/mxsfb/lcdif_kms.c
> > index dbd42cc1da87f82ef9cd4ccc70cdecbe56035174..21311cf5efee7d26c80316bffe80dd2bfed02238 100644
> > --- a/drivers/gpu/drm/mxsfb/lcdif_kms.c
> > +++ b/drivers/gpu/drm/mxsfb/lcdif_kms.c
> > @@ -433,7 +433,6 @@ static int lcdif_crtc_atomic_check(struct drm_crtc *crtc,
> >  	struct drm_connector *connector;
> >  	struct drm_encoder *encoder;
> >  	struct drm_bridge_state *bridge_state;
> > -	struct drm_bridge *bridge;
> >  	u32 bus_format, bus_flags;
> >  	bool format_set = false, flags_set = false;
> >  	int ret, i;
> > @@ -448,6 +447,8 @@ static int lcdif_crtc_atomic_check(struct drm_crtc *crtc,
> >  
> >  	/* Try to find consistent bus format and flags across first bridges. */
> >  	for_each_new_connector_in_state(state, connector, connector_state, i) {
> > +		struct drm_bridge *bridge __free(drm_bridge_put) = NULL;
> > +
> >  		if (!connector_state->crtc)
> >  			continue;  
> 
> To avoid the unnecessary cleanup for !connector_state->crtc, I would write:
> 
> -8<-
> --- a/drivers/gpu/drm/mxsfb/lcdif_kms.c
> +++ b/drivers/gpu/drm/mxsfb/lcdif_kms.c
> @@ -433,7 +433,6 @@ static int lcdif_crtc_atomic_check(struct drm_crtc *crtc,
>         struct drm_connector *connector;
>         struct drm_encoder *encoder;
>         struct drm_bridge_state *bridge_state;
> -       struct drm_bridge *bridge;
>         u32 bus_format, bus_flags;
>         bool format_set = false, flags_set = false;
>         int ret, i;
> @@ -453,7 +452,8 @@ static int lcdif_crtc_atomic_check(struct drm_crtc *crtc,
>  
>                 encoder = connector_state->best_encoder;
>  
> -               bridge = drm_bridge_chain_get_first_bridge(encoder);
> +               struct drm_bridge *bridge __free(drm_bridge_put) =
> +                               drm_bridge_chain_get_first_bridge(encoder);

Good idea, I probably didn't think about it because I was grown up in a
world where all declarations must before the code. :-)

Changing this in v9.

Luca

-- 
Luca Ceresoli, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com