Re: [PATCH] drm: bridge: thc63lvd1024: Print error message when DT parsing fails

From: Sui Jingfeng <sui.jingfeng@linux.dev>
To: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>,
	dri-devel@lists.freedesktop.org
Cc: Andrzej Hajda <andrzej.hajda@intel.com>,
	Neil Armstrong <neil.armstrong@linaro.org>,
	Robert Foss <rfoss@kernel.org>, Jonas Karlman <jonas@kwiboo.se>,
	Jernej Skrabec <jernej.skrabec@gmail.com>
Subject: Re: [PATCH] drm: bridge: thc63lvd1024: Print error message when DT parsing fails
Date: Tue, 19 Mar 2024 00:42:41 +0800	[thread overview]
Message-ID: <78739dfe-c6ee-44bd-a2e6-2ced24ff15c1@linux.dev> (raw)
In-Reply-To: <20240318160601.2813-1-laurent.pinchart+renesas@ideasonboard.com>

Hi,

On 2024/3/19 00:06, Laurent Pinchart wrote:
> Commit 00084f0c01bf ("drm: bridge: thc63lvd1024: Switch to use
> of_graph_get_remote_node()") simplified the thc63lvd1024 driver by
> replacing hand-rolled code with a helper function.

[...]

> While doing so, it
> created an error code path at probe time without any error message,

If this is a reason or a concern, then every drm bridges drivers will suffer from
such a concern. Right?

> potentially causing probe issues that get annoying to debug.

Sorry, let's keep it fair enough, it creates nothing annoyed.

If there is a probe issues, then, it is caused by ill-behavioral DT.
*NOT* my patch. And should be found during review stage.

If the of_graph_get_remote_node() function is not good enough,
I suggest to improve the of_graph_get_remote_node() function,
then all callers of it will benefits.

Well, the strong word here just terrifying new programmers to call
core function helpers. Please use more *soft* description in the
commit message.

> Fix it by
> adding an error message.
>
> Fixes: 00084f0c01bf ("drm: bridge: thc63lvd1024: Switch to use of_graph_get_remote_node()")

Please drop the fixes tag at here, append the tag to a real bug-fix patch will make more sense imo.
I suggest to improve the of_graph_get_remote_node() function, then all callers of it will benefits.
NOT a single implement like this.

> Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
> ---
>   drivers/gpu/drm/bridge/thc63lvd1024.c | 5 ++++-
>   1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/bridge/thc63lvd1024.c b/drivers/gpu/drm/bridge/thc63lvd1024.c
> index 5f99f9724081..674efc489e3a 100644
> --- a/drivers/gpu/drm/bridge/thc63lvd1024.c
> +++ b/drivers/gpu/drm/bridge/thc63lvd1024.c
> @@ -125,8 +125,11 @@ static int thc63_parse_dt(struct thc63_dev *thc63)
>   
>   	remote = of_graph_get_remote_node(thc63->dev->of_node,
>   					  THC63_RGB_OUT0, -1);
> -	if (!remote)
> +	if (!remote) {
> +		dev_err(thc63->dev, "No remote endpoint for port@%u\n",
> +			THC63_RGB_OUT0);
>   		return -ENODEV;
> +	}
>   
>   	thc63->next = of_drm_find_bridge(remote);
>   	of_node_put(remote);
>
> base-commit: 00084f0c01bf3a2591d007010b196e048281c455

-- 
Best regards,
Sui