linux-kernel - Re: [RFC 03/10] [media] vb2: add in-fence support to QBUF

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Date:   Mon, 3 Apr 2017 14:27:42 -0400
From:   Javier Martinez Canillas <javier@....samsung.com>
To:     Gustavo Padovan <gustavo@...ovan.org>, linux-media@...r.kernel.org
Cc:     Hans Verkuil <hverkuil@...all.nl>,
        Mauro Carvalho Chehab <mchehab@....samsung.com>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        linux-kernel@...r.kernel.org,
        Gustavo Padovan <gustavo.padovan@...labora.com>
Subject: Re: [RFC 03/10] [media] vb2: add in-fence support to QBUF

Hello Gustavo,

On 03/13/2017 04:20 PM, Gustavo Padovan wrote:

[snip]

>  
>  int vb2_qbuf(struct vb2_queue *q, struct v4l2_buffer *b)
>  {
> +	struct dma_fence *fence = NULL;
>  	int ret;
>  
>  	if (vb2_fileio_is_active(q)) {
> @@ -565,7 +567,17 @@ int vb2_qbuf(struct vb2_queue *q, struct v4l2_buffer *b)
>  	}
>  
>  	ret = vb2_queue_or_prepare_buf(q, b, "qbuf");
> -	return ret ? ret : vb2_core_qbuf(q, b->index, b);
> +
> +	if (b->flags & V4L2_BUF_FLAG_IN_FENCE) {
> +		if (b->memory != VB2_MEMORY_DMABUF)
> +			return -EINVAL;
> +

I wonder if is correct to check this. Only one side of the pipeline uses
V4L2_MEMORY_DMABUF while the other uses V4L2_MEMORY_MMAP + VIDIOC_EXPBUF.

So that means that fences can only be used in one direction?

Best regards,
-- 
Javier Martinez Canillas
Open Source Group
Samsung Research America