linux-kernel - Re: [PATCH] drm/bridge: panel: Return always an error pointer in drm_panel_bridge

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Date:   Fri, 17 Apr 2020 00:46:35 +0300
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Enric Balletbo i Serra <enric.balletbo@...labora.com>
Cc:     linux-kernel@...r.kernel.org,
        Collabora Kernel ML <kernel@...labora.com>, sam@...nborg.org,
        Andrzej Hajda <a.hajda@...sung.com>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...ux.ie>,
        Jernej Skrabec <jernej.skrabec@...l.net>,
        Jonas Karlman <jonas@...boo.se>,
        Neil Armstrong <narmstrong@...libre.com>,
        dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH] drm/bridge: panel: Return always an error pointer in
 drm_panel_bridge_add()

Hi Enric,

Thank you for the patch.

On Thu, Apr 16, 2020 at 11:06:54PM +0200, Enric Balletbo i Serra wrote:
> Since commit 89958b7cd955 ("drm/bridge: panel: Infer connector type from
> panel by default"), drm_panel_bridge_add() and their variants can return
> NULL and an error pointer. This is fine but none of the actual users of
> the API are checking for the NULL value. Instead of change all the
> users, seems reasonable to return an error pointer instead. So change
> the returned value for those functions when the connector type is unknown.
> 
> Suggested-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>
> Signed-off-by: Enric Balletbo i Serra <enric.balletbo@...labora.com>

Reviewed-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>

> ---
> 
>  drivers/gpu/drm/bridge/panel.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/bridge/panel.c b/drivers/gpu/drm/bridge/panel.c
> index 8461ee8304ba..7a3df0f319f3 100644
> --- a/drivers/gpu/drm/bridge/panel.c
> +++ b/drivers/gpu/drm/bridge/panel.c
> @@ -166,7 +166,7 @@ static const struct drm_bridge_funcs panel_bridge_bridge_funcs = {
>   *
>   * The connector type is set to @panel->connector_type, which must be set to a
>   * known type. Calling this function with a panel whose connector type is
> - * DRM_MODE_CONNECTOR_Unknown will return NULL.
> + * DRM_MODE_CONNECTOR_Unknown will return ERR_PTR(-EINVAL).
>   *
>   * See devm_drm_panel_bridge_add() for an automatically managed version of this
>   * function.
> @@ -174,7 +174,7 @@ static const struct drm_bridge_funcs panel_bridge_bridge_funcs = {
>  struct drm_bridge *drm_panel_bridge_add(struct drm_panel *panel)
>  {
>  	if (WARN_ON(panel->connector_type == DRM_MODE_CONNECTOR_Unknown))
> -		return NULL;
> +		return ERR_PTR(-EINVAL);
>  
>  	return drm_panel_bridge_add_typed(panel, panel->connector_type);
>  }
> @@ -265,7 +265,7 @@ struct drm_bridge *devm_drm_panel_bridge_add(struct device *dev,
>  					     struct drm_panel *panel)
>  {
>  	if (WARN_ON(panel->connector_type == DRM_MODE_CONNECTOR_Unknown))
> -		return NULL;
> +		return ERR_PTR(-EINVAL);
>  
>  	return devm_drm_panel_bridge_add_typed(dev, panel,
>  					       panel->connector_type);

-- 
Regards,

Laurent Pinchart