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

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Date: Mon, 18 Mar 2024 17:57:26 +0200
From: Laurent Pinchart <laurent.pinchart@...asonboard.com>
To: Sui Jingfeng <sui.jingfeng@...ux.dev>
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()

On Mon, Mar 18, 2024 at 11:53:11PM +0800, Sui Jingfeng wrote:
> On 2024/3/18 23:33, Laurent Pinchart wrote:
> > 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.

I'm actually build-testing a patch I already wrote :-) I'll post it in a
moment.

> >>   		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);

-- 
Regards,

Laurent Pinchart