linux-kernel - Re: [PATCH] media: ov2680: register the v4l2 subdev async at the end of probe

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Date:   Sat, 1 Sep 2018 14:46:29 +0300
From:   Sakari Ailus <sakari.ailus@....fi>
To:     Javier Martinez Canillas <javierm@...hat.com>
Cc:     linux-kernel@...r.kernel.org,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Rui Miguel Silva <rmfrfs@...il.com>,
        linux-media@...r.kernel.org
Subject: Re: [PATCH] media: ov2680: register the v4l2 subdev async at the end
 of probe

Hi Javier,

On Fri, Aug 31, 2018 at 05:19:06PM +0200, Javier Martinez Canillas wrote:
> The driver registers the subdev async in the middle of the probe function
> but this has to be done at the very end of the probe function to prevent
> registering a device whose probe function could fail (i.e: the clock and
> regulators enable can fail, the I2C transfers could return errors, etc).
> 
> It could also lead to a media device driver that is waiting to bound the
> v4l2 subdevice to incorrectly expose its media device to userspace, since
> the subdev is registered but later its media entity is cleaned up on error.
> 
> Fixes: 3ee47cad3e69 ("media: ov2680: Add Omnivision OV2680 sensor driver")
> Signed-off-by: Javier Martinez Canillas <javierm@...hat.com>
> 
> ---
> 
>  drivers/media/i2c/ov2680.c | 9 ++++-----
>  1 file changed, 4 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/media/i2c/ov2680.c b/drivers/media/i2c/ov2680.c
> index f753a1c333ef..2ef920a17278 100644
> --- a/drivers/media/i2c/ov2680.c
> +++ b/drivers/media/i2c/ov2680.c
> @@ -983,10 +983,6 @@ static int ov2680_v4l2_init(struct ov2680_dev *sensor)
>  
>  	sensor->sd.ctrl_handler = hdl;
>  
> -	ret = v4l2_async_register_subdev(&sensor->sd);
> -	if (ret < 0)
> -		goto cleanup_entity;
> -
>  	return 0;
>  
>  cleanup_entity:
> @@ -1096,6 +1092,10 @@ static int ov2680_probe(struct i2c_client *client)
>  	if (ret < 0)
>  		goto error_cleanup;

How about instead moving ov2680_check_id() call earlier in probe()? That
would seem to be a better fix: the driver should check the device is around
before registering anything.

>  
> +	ret = v4l2_async_register_subdev(&sensor->sd);
> +	if (ret < 0)
> +		goto error_cleanup;
> +
>  	dev_info(dev, "ov2680 init correctly\n");
>  
>  	return 0;
> @@ -1104,7 +1104,6 @@ static int ov2680_probe(struct i2c_client *client)
>  	dev_err(dev, "ov2680 init fail: %d\n", ret);
>  
>  	media_entity_cleanup(&sensor->sd.entity);
> -	v4l2_async_unregister_subdev(&sensor->sd);
>  	v4l2_ctrl_handler_free(&sensor->ctrls.handler);
>  
>  lock_destroy:

-- 
Regards,

Sakari Ailus
e-mail: sakari.ailus@....fi