linux-kernel - Re: [PATCH 03/13] media: i2c: Defer probe if not endpoint found

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Date:   Fri, 23 Jul 2021 09:49:12 +0200
From:   Paul Kocialkowski <paul.kocialkowski@...tlin.com>
To:     Daniel Scally <djrscally@...il.com>
Cc:     Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Ezequiel Garcia <ezequiel@...labora.com>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        Yang Li <yang.lee@...ux.alibaba.com>,
        "open list:MEDIA INPUT INFRASTRUCTURE (V4L/DVB)" 
        <linux-media@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        Yong Zhi <yong.zhi@...el.com>,
        Bingbu Cao <bingbu.cao@...el.com>,
        Tianshu Qiu <tian.shu.qiu@...el.com>,
        Colin Ian King <colin.king@...onical.com>,
        laurent.pinchart@...asonboard.com, kieran.bingham@...asonboard.com
Subject: Re: [PATCH 03/13] media: i2c: Defer probe if not endpoint found

Hi Daniel,

On Thu 22 Jul 21, 21:33, Daniel Scally wrote:
> The ov8865 driver is one of those that can be connected to a CIO2
> device by the cio2-bridge code. This means that the absence of an
> endpoint for this device is not necessarily fatal, as one might be
> built by the cio2-bridge when it probes. Return -EPROBE_DEFER if no
> endpoint is found rather than a fatal error.

Is this an error that you have actually seen in practice?

My understanding is that this function should return the handle to the *local*
fwnode graph endpoint, which relates to the static device-tree description
and should be unrelated to another driver probing.

So as far as I can see, this should not be needed (but correct me if I'm wrong).

Cheers,

Paul

> Signed-off-by: Daniel Scally <djrscally@...il.com>
> ---
>  drivers/media/i2c/ov8865.c | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/media/i2c/ov8865.c b/drivers/media/i2c/ov8865.c
> index 2ef146e7e7ef..66182142c28b 100644
> --- a/drivers/media/i2c/ov8865.c
> +++ b/drivers/media/i2c/ov8865.c
> @@ -2796,10 +2796,8 @@ static int ov8865_probe(struct i2c_client *client)
>  	/* Graph Endpoint */
>  
>  	handle = fwnode_graph_get_next_endpoint(dev_fwnode(dev), NULL);
> -	if (!handle) {
> -		dev_err(dev, "unable to find endpoint node\n");
> -		return -EINVAL;
> -	}
> +	if (!handle)
> +		return -EPROBE_DEFER;
>  
>  	sensor->endpoint.bus_type = V4L2_MBUS_CSI2_DPHY;
>  
> -- 
> 2.25.1
> 

-- 
Paul Kocialkowski, Bootlin
Embedded Linux and kernel engineering
https://bootlin.com

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