linux-kernel - Re: [PATCH] drm: bridge: thc63lvd1024: Switch to use of_graph_get_remote

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Date: Mon, 18 Mar 2024 23:53:11 +0800
From: Sui Jingfeng <sui.jingfeng@...ux.dev>
To: Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc: Andrzej Hajda <andrzej.hajda@...el.com>,
 Neil Armstrong <neil.armstrong@...aro.org>, Robert Foss <rfoss@...nel.org>,
 Jonas Karlman <jonas@...boo.se>, Jernej Skrabec <jernej.skrabec@...il.com>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
 David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>,
 dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm: bridge: thc63lvd1024: Switch to use
 of_graph_get_remote_node()

Hi,


On 2024/3/18 23:33, Laurent Pinchart wrote:
> Hi Sui,
>
> Thank you for the patch.
>
> On Sun, Mar 17, 2024 at 01:28:00AM +0800, Sui Jingfeng wrote:
>> To reduce boilerplate, use of_graph_get_remote_node() helper instead of
>> the hand-rolling code.
>>
>> Signed-off-by: Sui Jingfeng <sui.jingfeng@...ux.dev>
>> ---
>>   drivers/gpu/drm/bridge/thc63lvd1024.c | 24 +++---------------------
>>   1 file changed, 3 insertions(+), 21 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/bridge/thc63lvd1024.c b/drivers/gpu/drm/bridge/thc63lvd1024.c
>> index d4c1a601bbb5..5f99f9724081 100644
>> --- a/drivers/gpu/drm/bridge/thc63lvd1024.c
>> +++ b/drivers/gpu/drm/bridge/thc63lvd1024.c
>> @@ -123,28 +123,10 @@ static int thc63_parse_dt(struct thc63_dev *thc63)
>>   	struct device_node *endpoint;
>>   	struct device_node *remote;
>>   
>> -	endpoint = of_graph_get_endpoint_by_regs(thc63->dev->of_node,
>> -						 THC63_RGB_OUT0, -1);
>> -	if (!endpoint) {
>> -		dev_err(thc63->dev, "Missing endpoint in port@%u\n",
>> -			THC63_RGB_OUT0);
>> -		return -ENODEV;
>> -	}
>> -
>> -	remote = of_graph_get_remote_port_parent(endpoint);
>> -	of_node_put(endpoint);
>> -	if (!remote) {
>> -		dev_err(thc63->dev, "Endpoint in port@%u unconnected\n",
>> -			THC63_RGB_OUT0);
>> +	remote = of_graph_get_remote_node(thc63->dev->of_node,
>> +					  THC63_RGB_OUT0, -1);
>> +	if (!remote)
> The old logic is equivalent to of_graph_get_remote_node(), but now the
> driver will fail probing without an error message. That's not very nice
> as it leads to difficult to debug problems. I would keep one dev_err()
> here:
>
> 		dev_err(thc63->dev, "No remote endpoint for port@%u\n",
> 			THC63_RGB_OUT0);
>
> As your patch has been merged already, would you like to post a
> follow-up patch to fix this ?


Yes, this is indeed a difference. I will post a follow-up patch to fix this.


>>   		return -ENODEV;
>> -	}
>> -
>> -	if (!of_device_is_available(remote)) {
>> -		dev_err(thc63->dev, "port@%u remote endpoint is disabled\n",
>> -			THC63_RGB_OUT0);
>> -		of_node_put(remote);
>> -		return -ENODEV;
>> -	}
>>   
>>   	thc63->next = of_drm_find_bridge(remote);
>>   	of_node_put(remote);

-- 
Best regards,
Sui