[libcamera-devel] [PATCH] simple-cam: Move camera detection check to where it belongs

[paul.elder at ideasonboard.com]

Hi Laurent,

On Mon, Sep 27, 2021 at 12:05:54AM +0300, Laurent Pinchart wrote:
> Commit 14529b6d1c4a ("simple-cam: Early return if no cameras are found
> on the system") added a check to ensure that at least one camera is
> present in the system to avoid a crash otherwise. The check was however
> placed towards the end of the main() function, way after the camera is
> accessed, possibly due to a rebase conflict. Move it before accessing
> the first camera.
> 
> While at it, replace usage of std::vector::size() with
> std::vector::empty() which expresses the intent better.
> 
> Fixes: 14529b6d1c4a ("simple-cam: Early return if no cameras are found on the system")
> Signed-off-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>

Reviewed-by: Paul Elder <paul.elder at ideasonboard.com>

> ---
>  simple-cam.cpp | 17 +++++++++--------
>  1 file changed, 9 insertions(+), 8 deletions(-)
> 
> diff --git a/simple-cam.cpp b/simple-cam.cpp
> index e374e45849dc..71a715a0c27d 100644
> --- a/simple-cam.cpp
> +++ b/simple-cam.cpp
> @@ -163,13 +163,21 @@ int main()
>  	 * Application lock usage of Camera by 'acquiring' them.
>  	 * Once done with it, application shall similarly 'release' the Camera.
>  	 *
> -	 * As an example, use the first available camera in the system.
> +	 * As an example, use the first available camera in the system after
> +	 * making sure that at least one camera is available.
>  	 *
>  	 * Cameras can be obtained by their ID or their index, to demonstrate
>  	 * this, the following code gets the ID of the first camera; then gets
>  	 * the camera associated with that ID (which is of course the same as
>  	 * cm->cameras()[0]).
>  	 */
> +	if (cm->cameras().empty()) {
> +		std::cout << "No cameras were identified on the system."
> +			  << std::endl;
> +		cm->stop();
> +		return EXIT_FAILURE;
> +	}
> +
>  	std::string cameraId = cm->cameras()[0]->id();
>  	camera = cm->get(cameraId);
>  	camera->acquire();
> @@ -386,13 +394,6 @@ int main()
>  	for (std::unique_ptr<Request> &request : requests)
>  		camera->queueRequest(request.get());
>  
> -	if (!cm->cameras().size()) {
> -		std::cout << "No cameras were identified on the system."
> -			  << std::endl;
> -		cm->stop();
> -		return EXIT_FAILURE;
> -	}
> -
>  	/*
>  	 * --------------------------------------------------------------------
>  	 * Run an EventLoop
> 
> base-commit: 1f795410c0d99aaa15c8155d7d16ae6357487a96
> prerequisite-patch-id: a9984c79d9b952f4004a670f8828600af70d732e
> prerequisite-patch-id: 8dcf991243c61f7931da9f18ed5acd4920ea32c5
> -- 
> Regards,
> 
> Laurent Pinchart
>