linux-kernel - Re: [PATCH v3 1/2] media: uvcvideo: Fix deferred probing error

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Message-ID: <20250422180630.GJ17813@pendragon.ideasonboard.com>
Date: Tue, 22 Apr 2025 21:06:30 +0300
From: Laurent Pinchart <laurent.pinchart@...asonboard.com>
To: Ricardo Ribalda <ribalda@...omium.org>
Cc: Hans de Goede <hdegoede@...hat.com>,
	Mauro Carvalho Chehab <mchehab@...nel.org>,
	Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
	linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
	stable@...r.kernel.org, Douglas Anderson <dianders@...omium.org>
Subject: Re: [PATCH v3 1/2] media: uvcvideo: Fix deferred probing error

Hi Ricardo,

Thank you for the patch.

On Thu, Mar 13, 2025 at 12:20:39PM +0000, Ricardo Ribalda wrote:
> uvc_gpio_parse() can return -EPROBE_DEFER when the GPIOs it depends on
> have not yet been probed. This return code should be propagated to the
> caller of uvc_probe() to ensure that probing is retried when the required
> GPIOs become available.
> 
> Currently, this error code is incorrectly converted to -ENODEV,
> causing some internal cameras to be ignored.
> 
> This commit fixes this issue by propagating the -EPROBE_DEFER error.
> 
> Cc: stable@...r.kernel.org
> Fixes: 2886477ff987 ("media: uvcvideo: Implement UVC_EXT_GPIO_UNIT")
> Reviewed-by: Douglas Anderson <dianders@...omium.org>
> Signed-off-by: Ricardo Ribalda <ribalda@...omium.org>
> ---
>  drivers/media/usb/uvc/uvc_driver.c | 27 +++++++++++++++++++--------
>  1 file changed, 19 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/media/usb/uvc/uvc_driver.c b/drivers/media/usb/uvc/uvc_driver.c
> index deadbcea5e227c832976fd176c7cdbfd7809c608..e966bdb9239f345fd157588ebdad2b3ebe45168d 100644
> --- a/drivers/media/usb/uvc/uvc_driver.c
> +++ b/drivers/media/usb/uvc/uvc_driver.c
> @@ -2231,13 +2231,16 @@ static int uvc_probe(struct usb_interface *intf,
>  #endif
>  
>  	/* Parse the Video Class control descriptor. */
> -	if (uvc_parse_control(dev) < 0) {
> +	ret = uvc_parse_control(dev);
> +	if (ret < 0) {
> +		ret = -ENODEV;

Why do you set ret to -ENODEV here...

>  		uvc_dbg(dev, PROBE, "Unable to parse UVC descriptors\n");
>  		goto error;
>  	}
>  
>  	/* Parse the associated GPIOs. */
> -	if (uvc_gpio_parse(dev) < 0) {
> +	ret = uvc_gpio_parse(dev);
> +	if (ret < 0) {
>  		uvc_dbg(dev, PROBE, "Unable to parse UVC GPIOs\n");
>  		goto error;
>  	}
> @@ -2263,24 +2266,32 @@ static int uvc_probe(struct usb_interface *intf,
>  	}
>  
>  	/* Register the V4L2 device. */
> -	if (v4l2_device_register(&intf->dev, &dev->vdev) < 0)
> +	ret = v4l2_device_register(&intf->dev, &dev->vdev);
> +	if (ret < 0)

... but not here ? The code below is also not very consistant.

>  		goto error;
>  
>  	/* Scan the device for video chains. */
> -	if (uvc_scan_device(dev) < 0)
> +	if (uvc_scan_device(dev) < 0) {
> +		ret = -ENODEV;
>  		goto error;
> +	}
>  
>  	/* Initialize controls. */
> -	if (uvc_ctrl_init_device(dev) < 0)
> +	if (uvc_ctrl_init_device(dev) < 0) {
> +		ret = -ENODEV;
>  		goto error;
> +	}
>  
>  	/* Register video device nodes. */
> -	if (uvc_register_chains(dev) < 0)
> +	if (uvc_register_chains(dev) < 0) {
> +		ret = -ENODEV;
>  		goto error;
> +	}
>  
>  #ifdef CONFIG_MEDIA_CONTROLLER
>  	/* Register the media device node */
> -	if (media_device_register(&dev->mdev) < 0)
> +	ret = media_device_register(&dev->mdev);
> +	if (ret < 0)
>  		goto error;
>  #endif
>  	/* Save our data pointer in the interface data. */
> @@ -2314,7 +2325,7 @@ static int uvc_probe(struct usb_interface *intf,
>  error:
>  	uvc_unregister_video(dev);
>  	kref_put(&dev->ref, uvc_delete);
> -	return -ENODEV;
> +	return ret;
>  }
>  
>  static void uvc_disconnect(struct usb_interface *intf)

-- 
Regards,

Laurent Pinchart