[PATCH v2] libcamera: udev: Catch udev notification errors

[Laurent Pinchart]

Hi Kieran,

Thank you for the patch.

On Wed, Aug 07, 2024 at 02:49:50PM +0100, Kieran Bingham wrote:
> The udev_monitor_receive_device() can return NULL on an error as
> detailed in the man pages for the function.
> 
> The udevNotify() handler in the DeviceEnumeratorUdev directly uses the
> return value of udev_monitor_receive_device() in successive calls to
> process the event without having first checked the udev_device.
> 
> Ensure we identify, and handle events where the udev_device can not be
> returned successfully.
> 
> Bug: https://bugs.libcamera.org/show_bug.cgi?id=230
> Reviewed-by: Stefan Klug <stefan.klug at ideasonboard.com>
> Signed-off-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
> 
> ---
> v2:
>  - Report strerror based on errno from the udev_monitor_receive_device()
>    call.
> 
>  src/libcamera/device_enumerator_udev.cpp | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/src/libcamera/device_enumerator_udev.cpp b/src/libcamera/device_enumerator_udev.cpp
> index 01c70b6daa82..53eeb772d900 100644
> --- a/src/libcamera/device_enumerator_udev.cpp
> +++ b/src/libcamera/device_enumerator_udev.cpp
> @@ -332,6 +332,14 @@ int DeviceEnumeratorUdev::addV4L2Device(dev_t devnum)
>  void DeviceEnumeratorUdev::udevNotify()
>  {
>  	struct udev_device *dev = udev_monitor_receive_device(monitor_);
> +	if (!dev) {
> +		int error = errno;

grepping for ' = errno' gives me 12 variables named ret, and one named
err. I'd go for 'ret' here too for consitency.

Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>

Could you ask the bug reporter to test this patch and tell what error
number they get ?

> +		LOG(DeviceEnumerator, Warning)
> +			<< "Ignoring notfication received without a device: "
> +			<< strerror(error);
> +		return;
> +	}
> +
>  	std::string_view action(udev_device_get_action(dev));
>  	std::string_view deviceNode(udev_device_get_devnode(dev));
>  

-- 
Regards,

Laurent Pinchart