Hi Sumit,
Thanks for the patch!
Sumit Semwal wrote:
...
> @@ -962,6 +1030,109 @@ static int __qbuf_mmap(struct vb2_buffer *vb, const
> struct v4l2_buffer *b)
> }
>
> /**
> + * __qbuf_dmabuf() - handle qbuf of a DMABUF buffer
> + */
> +static int __qbuf_dmabuf(struct vb2_buffer *vb, const struct v4l2_buffer *b)
> +{
> + struct v4l2_plane planes[VIDEO_MAX_PLANES];
> + struct vb2_queue *q = vb->vb2_queue;
> + void *mem_priv;
> + unsigned int plane;
> + int ret;
> + int write = !V4L2_TYPE_IS_OUTPUT(q->type);
> +
> + /* Verify and copy relevant information provided by the userspace */
> + ret = __fill_vb2_buffer(vb, b, planes);
> + if (ret)
> + return ret;
> +
> + for (plane = 0; plane < vb->num_planes; ++plane) {
> + struct dma_buf *dbuf = dma_buf_get(planes[plane].m.fd);
> +
> + if (IS_ERR_OR_NULL(dbuf)) {
> + dprintk(1, "qbuf: invalid dmabuf fd for "
> + "plane %d\n", plane);
> + ret = PTR_ERR(dbuf);
> + goto err;
> + }
> +
> + /* this doesn't get filled in until __fill_vb2_buffer(),
> + * since it isn't known until after dma_buf_get()..
> + */
> + planes[plane].length = dbuf->size;
> +
> + /* Skip the plane if already verified */
> + if (dbuf == vb->planes[plane].dbuf) {
> + dma_buf_put(dbuf);
> + continue;
> + }
> +
> + dprintk(3, "qbuf: buffer description for plane %d changed, "
> + "reattaching dma buf\n", plane);
> +
> + /* Release previously acquired memory if present */
> + if (vb->planes[plane].mem_priv) {
> + call_memop(q, plane, detach_dmabuf,
> + vb->planes[plane].mem_priv);
> + dma_buf_put(vb->planes[plane].dbuf);
> + }
> +
> + vb->planes[plane].mem_priv = NULL;
> +
> + /* Acquire each plane's memory */
> + mem_priv = q->mem_ops->attach_dmabuf(
> + q->alloc_ctx[plane], dbuf);
> + if (IS_ERR(mem_priv)) {
> + dprintk(1, "qbuf: failed acquiring dmabuf "
> + "memory for plane %d\n", plane);
> + ret = PTR_ERR(mem_priv);
> + goto err;
> + }
> +
> + vb->planes[plane].dbuf = dbuf;
> + vb->planes[plane].mem_priv = mem_priv;
> + }
> +
> + /* TODO: This pins the buffer(s) with dma_buf_map_attachment()).. but
> + * really we want to do this just before the DMA, not while queueing
> + * the buffer(s)..
> + */
> + for (plane = 0; plane < vb->num_planes; ++plane) {
> + ret = q->mem_ops->map_dmabuf(
> + vb->planes[plane].mem_priv, write);
> + if (ret) {
> + dprintk(1, "qbuf: failed mapping dmabuf "
> + "memory for plane %d\n", plane);
> + goto err;
> + }
> + }
Shouldn't the buffer mapping only be done at the first call to
__qbuf_dmabuf()? On latter calls, the cache would need to be handled
according to presence of V4L2_BUF_FLAG_NO_CACHE_CLEAN /
V4L2_BUF_FLAG_NO_CACHE_INVALIDATE in v4l2_buffer.
> + /*
> + * Call driver-specific initialization on the newly acquired buffer,
> + * if provided.
> + */
> + ret = call_qop(q, buf_init, vb);
> + if (ret) {
> + dprintk(1, "qbuf: buffer initialization failed\n");
> + goto err;
> + }
> +
> + /*
> + * Now that everything is in order, copy relevant information
> + * provided by userspace.
> + */
> + for (plane = 0; plane < vb->num_planes; ++plane)
> + vb->v4l2_planes[plane] = planes[plane];
> +
> + return 0;
> +err:
> + /* In case of errors, release planes that were already acquired */
> + __vb2_buf_dmabuf_put(vb);
> +
> + return ret;
> +}
> +
> +/**
> * __enqueue_in_driver() - enqueue a vb2_buffer in driver for processing
> */
> static void __enqueue_in_driver(struct vb2_buffer *vb)
> @@ -985,6 +1156,9 @@ static int __buf_prepare(struct vb2_buffer *vb, const
> struct v4l2_buffer *b)
> case V4L2_MEMORY_USERPTR:
> ret = __qbuf_userptr(vb, b);
> break;
> + case V4L2_MEMORY_DMABUF:
> + ret = __qbuf_dmabuf(vb, b);
> + break;
> default:
> WARN(1, "Invalid queue type\n");
> ret = -EINVAL;
> @@ -1284,6 +1458,7 @@ int vb2_dqbuf(struct vb2_queue *q, struct v4l2_buffer
> *b, bool nonblocking)
> {
> struct vb2_buffer *vb = NULL;
> int ret;
> + unsigned int plane;
>
> if (q->fileio) {
> dprintk(1, "dqbuf: file io in progress\n");
> @@ -1307,6 +1482,15 @@ int vb2_dqbuf(struct vb2_queue *q, struct v4l2_buffer
> *b, bool nonblocking)
> return ret;
> }
>
> + /* TODO: this unpins the buffer(dma_buf_unmap_attachment()).. but
> + * really we want tot do this just after DMA, not when the
> + * buffer is dequeued..
> + */
> + if (q->memory == V4L2_MEMORY_DMABUF)
> + for (plane = 0; plane < vb->num_planes; ++plane)
> + call_memop(q, plane, unmap_dmabuf,
> + vb->planes[plane].mem_priv);
> +
Same here, except reverse: this only should be done when the buffer is
destroyed --- either when the user explicitly calls reqbufs(0) or when
the file handle owning this buffer is being closed.
Mapping buffers at every prepare_buf and unmapping them in dqbuf is
prohibitively expensive. Same goes for many other APIs than V4L2, I think.
I wonder if the means to do this exists already.
I have to admit I haven't followed the dma_buf discussion closely so I
might be missing something relevant here.
Kind regards,
--
Sakari Ailus
sakari.ai...@iki.fi
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