[PATCH weston] clients/dmabuf-intel: use three buffers

[Yong Bakos]

On Jun 13, 2016, at 6:17 AM, Pekka Paalanen <ppaalanen at gmail.com> wrote:
> 
> From: Pekka Paalanen <pekka.paalanen at collabora.co.uk>
> 
> Use three buffers like simple-dmabuf-v4l instead of just two.
> 
> This is required, because when a frame callback arrives, the just
> committed buffer is only on its way to the screen, while the previous
> buffer is still being scanned out. It will take for the page flip to
> complete, before the previous buffer is release. However, we want to be
> able to repaint already at the frame callback, so three buffers can be
> necessary.
> 
> This patch fixes weston-simple-dmabuf-intel to not abort with "Both
> buffers busy at redraw()." when hardware overlays are used and the
> surface gets directly scanned out.
> 
> Signed-off-by: Pekka Paalanen <pekka.paalanen at collabora.co.uk>

While I could not test this, it's a straightforward change, and it
does touch all cases in simple-dmabuf-intel.

Reviewed-by: Yong Bakos <ybakos at humanoriented.com>

Regards,
yong


> ---
> clients/simple-dmabuf-intel.c | 23 +++++++++++------------
> 1 file changed, 11 insertions(+), 12 deletions(-)
> 
> diff --git a/clients/simple-dmabuf-intel.c b/clients/simple-dmabuf-intel.c
> index 2ac2200..2c8eb24 100644
> --- a/clients/simple-dmabuf-intel.c
> +++ b/clients/simple-dmabuf-intel.c
> @@ -74,12 +74,14 @@ struct buffer {
> 	unsigned long stride;
> };
> 
> +#define NUM_BUFFERS 3
> +
> struct window {
> 	struct display *display;
> 	int width, height;
> 	struct wl_surface *surface;
> 	struct xdg_surface *xdg_surface;
> -	struct buffer buffers[2];
> +	struct buffer buffers[NUM_BUFFERS];
> 	struct buffer *prev_buffer;
> 	struct wl_callback *callback;
> };
> @@ -341,7 +343,7 @@ create_window(struct display *display, int width, int height)
> 		assert(0);
> 	}
> 
> -	for (i = 0; i < 2; ++i) {
> +	for (i = 0; i < NUM_BUFFERS; ++i) {
> 		ret = create_dmabuf_buffer(display, &window->buffers[i],
> 		                               width, height);
> 
> @@ -360,7 +362,7 @@ destroy_window(struct window *window)
> 	if (window->callback)
> 		wl_callback_destroy(window->callback);
> 
> -	for (i = 0; i < 2; i++) {
> +	for (i = 0; i < NUM_BUFFERS; i++) {
> 		if (!window->buffers[i].buffer)
> 			continue;
> 
> @@ -379,16 +381,13 @@ destroy_window(struct window *window)
> static struct buffer *
> window_next_buffer(struct window *window)
> {
> -	struct buffer *buffer;
> +	int i;
> 
> -	if (!window->buffers[0].busy)
> -		buffer = &window->buffers[0];
> -	else if (!window->buffers[1].busy)
> -		buffer = &window->buffers[1];
> -	else
> -		return NULL;
> +	for (i = 0; i < NUM_BUFFERS; i++)
> +		if (!window->buffers[i].busy)
> +			return &window->buffers[i];
> 
> -	return buffer;
> +	return NULL;
> }
> 
> static const struct wl_callback_listener frame_listener;
> @@ -403,7 +402,7 @@ redraw(void *data, struct wl_callback *callback, uint32_t time)
> 	if (!buffer) {
> 		fprintf(stderr,
> 			!callback ? "Failed to create the first buffer.\n" :
> -			"Both buffers busy at redraw(). Server bug?\n");
> +			"All buffers busy at redraw(). Server bug?\n");
> 		abort();
> 	}
> 
> -- 
> 2.7.3
> 
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