linux-kernel - Re: [PATCH v8 2/5] drm/bridge: get the bridge returned by drm_bridge_chain_get_first

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Message-ID: <be6a4d90-2c6e-42be-9948-df1840fd2f83@nxp.com>
Date: Mon, 23 Jun 2025 10:56:13 +0800
From: Liu Ying <victor.liu@....com>
To: Luca Ceresoli <luca.ceresoli@...tlin.com>,
 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>
Cc: 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 2/5] drm/bridge: get the bridge returned by
 drm_bridge_chain_get_first_bridge()

On 06/21/2025, Luca Ceresoli wrote:
> drm_bridge_chain_get_first_bridge() returns a bridge pointer that the
> caller could hold for a long time. Increment the refcount of the returned
> bridge and document it must be put by the caller.

To make sure the incremented refcount is decremented once this patch is
applied, does it make sense to squash patch 3, 4 and 5 into this one?

> 
> Reviewed-by: Maxime Ripard <mripard@...nel.org>
> Signed-off-by: Luca Ceresoli <luca.ceresoli@...tlin.com>
> ---
> 
> This patch was added in v7.
> ---
>  include/drm/drm_bridge.h | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h
> index b110c5bba8c0612a71f749ad51345e7a8ccdc910..f98044581d67c380c3bc3a1943bd6ab09b764ec3 100644
> --- a/include/drm/drm_bridge.h
> +++ b/include/drm/drm_bridge.h
> @@ -1336,6 +1336,9 @@ drm_bridge_get_prev_bridge(struct drm_bridge *bridge)
>   * drm_bridge_chain_get_first_bridge() - Get the first bridge in the chain
>   * @encoder: encoder object
>   *
> + * The refcount of the returned bridge is incremented. Use drm_bridge_put()
> + * when done with it.
> + *
>   * RETURNS:
>   * the first bridge in the chain, or NULL if @encoder has no bridge attached
>   * to it.
> @@ -1343,8 +1346,8 @@ drm_bridge_get_prev_bridge(struct drm_bridge *bridge)
>  static inline struct drm_bridge *
>  drm_bridge_chain_get_first_bridge(struct drm_encoder *encoder)
>  {
> -	return list_first_entry_or_null(&encoder->bridge_chain,
> -					struct drm_bridge, chain_node);
> +	return drm_bridge_get(list_first_entry_or_null(&encoder->bridge_chain,
> +						       struct drm_bridge, chain_node));
>  }
>  
>  /**
> 

-- 
Regards,
Liu Ying