[libcamera-devel] [SimpleCam PATCH 3/4] simple-cam: Fix the Buffer Allocation guidance

[Jacopo Mondi]

Hi Kieran,

On Tue, Aug 24, 2021 at 03:24:49PM +0100, Kieran Bingham wrote:
> The Buffer Allocation notes contains a TODO. Improve the notes regarding
> the FrameBufferAllocation and remove the todo.
>
> Signed-off-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
> ---
>  simple-cam.cpp | 12 +++++++++---
>  1 file changed, 9 insertions(+), 3 deletions(-)
>
> diff --git a/simple-cam.cpp b/simple-cam.cpp
> index 2e646a5485c9..47c5dc9987bc 100644
> --- a/simple-cam.cpp
> +++ b/simple-cam.cpp
> @@ -274,10 +274,16 @@ int main()
>  	 * Buffer Allocation
>  	 *
>  	 * Now that a camera has been configured, it knows all about its
> -	 * Streams sizes and formats, so we now have to ask it to reserve
> -	 * memory for all of them.
> +	 * Streams sizes and formats. We need to provide buffers to store
> +	 * captured images in. An application might choose to provide buffers
> +	 * externally, for instance from a display driver which will render the
> +	 * captured images, however libcamera can also provide buffers from a
> +	 * configured camera.

What about one paragraph for each of the two use cases ?


	 * Streams sizes and formats. The captured images need to be stored in
         * memory buffers which can be either provided by the application to the
         * library, or allocated in the Camera memory and exposed to
         * the application by libcamera.
         *
         * An application can decide to allocate memory buffers from
         * elsewhere, in example in the memory of the display driver that
         * will render the captured frames, and provide them to
         * libcamera to capture images there.
         *
         * Alternatively libcamera can help the application by providing
         * buffers allocated in the Camera memory by the usage of a
         * FrameBufferAllocator instance, which references the
         * (configured) Camera for which the application wishes to
         * allocated buffers for.
         */

feel free to take whatever or ignore.

Reviewed-by: Jacopo Mondi <jacopo at jmondi.org>

Thanks
   j


> +	 *
> +	 * To request buffers from libcamera, we use the FrameBufferAllocator,
> +	 * and reference the (configured) camera for which we wish to allocate
> +	 * buffers for.
>  	 */
> -	/* TODO: Update the comment here too */
>  	FrameBufferAllocator *allocator = new FrameBufferAllocator(camera);
>
>  	for (StreamConfiguration &cfg : *config) {
> --
> 2.30.2
>