Re: [PATCH 03/11] v4l: vb2: add support for shared buffer (dma_buf)

["Rémi Denis-Courmont" <remi@remlab.net>]

Le jeudi 5 avril 2012 17:00:00 Tomasz Stanislawski, vous avez écrit :
> From: Sumit Semwal <sumit.semwal@ti.com>
> 
> This patch adds support for DMABUF memory type in videobuf2. It calls
> relevant APIs of dma_buf for v4l reqbuf / qbuf / dqbuf operations.
> 
> For this version, the support is for videobuf2 as a user of the shared
> buffer; so the allocation of the buffer is done outside of V4L2. [A sample
> allocator of dma-buf shared buffer is given at [1]]
> 
> [1]: Rob Clark's DRM:
>    https://github.com/robclark/kernel-omap4/commits/drmplane-dmabuf
> 
> Signed-off-by: Tomasz Stanislawski <t.stanislaws@samsung.com>
>    [original work in the PoC for buffer sharing]
> Signed-off-by: Sumit Semwal <sumit.semwal@ti.com>
> Signed-off-by: Sumit Semwal <sumit.semwal@linaro.org>
> ---
>  drivers/media/video/videobuf2-core.c |  184
> +++++++++++++++++++++++++++++++++- include/media/videobuf2-core.h       | 
>  31 ++++++
>  2 files changed, 214 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/media/video/videobuf2-core.c
> b/drivers/media/video/videobuf2-core.c index 2e8f1df..b37feea 100644
> --- a/drivers/media/video/videobuf2-core.c
> +++ b/drivers/media/video/videobuf2-core.c
> @@ -106,6 +106,27 @@ static void __vb2_buf_userptr_put(struct vb2_buffer
> *vb) }
> 
>  /**
> + * __vb2_buf_dmabuf_put() - release memory associated with
> + * a DMABUF shared buffer
> + */
> +static void __vb2_buf_dmabuf_put(struct vb2_buffer *vb)
> +{
> +	struct vb2_queue *q = vb->vb2_queue;
> +	unsigned int plane;
> +
> +	for (plane = 0; plane < vb->num_planes; ++plane) {
> +		void *mem_priv = vb->planes[plane].mem_priv;
> +
> +		if (mem_priv) {
> +			call_memop(q, detach_dmabuf, mem_priv);
> +			dma_buf_put(vb->planes[plane].dbuf);
> +			vb->planes[plane].dbuf = NULL;
> +			vb->planes[plane].mem_priv = NULL;
> +		}
> +	}
> +}
> +
> +/**
>   * __setup_offsets() - setup unique offsets ("cookies") for every plane in
>   * every buffer on the queue
>   */
> @@ -227,6 +248,8 @@ static void __vb2_free_mem(struct vb2_queue *q,
> unsigned int buffers) /* Free MMAP buffers or release USERPTR buffers */
>  		if (q->memory == V4L2_MEMORY_MMAP)
>  			__vb2_buf_mem_free(vb);

Missing 'else' here? A switch() statement might be better?

> +		if (q->memory == V4L2_MEMORY_DMABUF)
> +			__vb2_buf_dmabuf_put(vb);
>  		else
>  			__vb2_buf_userptr_put(vb);
>  	}
> @@ -349,6 +372,12 @@ static int __fill_v4l2_buffer(struct vb2_buffer *vb,
> struct v4l2_buffer *b) */
>  		memcpy(b->m.planes, vb->v4l2_planes,
>  			b->length * sizeof(struct v4l2_plane));
> +
> +		if (q->memory == V4L2_MEMORY_DMABUF) {
> +			unsigned int plane;
> +			for (plane = 0; plane < vb->num_planes; ++plane)
> +				b->m.planes[plane].m.fd = 0;
> +		}
>  	} else {
>  		/*
>  		 * We use length and offset in v4l2_planes array even for
> @@ -360,6 +389,8 @@ static int __fill_v4l2_buffer(struct vb2_buffer *vb,
> struct v4l2_buffer *b) b->m.offset = vb->v4l2_planes[0].m.mem_offset;
>  		else if (q->memory == V4L2_MEMORY_USERPTR)
>  			b->m.userptr = vb->v4l2_planes[0].m.userptr;
> +		else if (q->memory == V4L2_MEMORY_DMABUF)
> +			b->m.fd = 0;
>  	}
> 
>  	/*
> @@ -451,6 +482,21 @@ static int __verify_mmap_ops(struct vb2_queue *q)
>  }
> 
>  /**
> + * __verify_dmabuf_ops() - verify that all memory operations required for
> + * DMABUF queue type have been provided
> + */
> +static int __verify_dmabuf_ops(struct vb2_queue *q)
> +{
> +	if (!(q->io_modes & VB2_DMABUF) || !q->mem_ops->attach_dmabuf
> +			|| !q->mem_ops->detach_dmabuf
> +			|| !q->mem_ops->map_dmabuf
> +			|| !q->mem_ops->unmap_dmabuf)
> +		return -EINVAL;
> +
> +	return 0;
> +}
> +
> +/**
>   * vb2_reqbufs() - Initiate streaming
>   * @q:		videobuf2 queue
>   * @req:	struct passed from userspace to vidioc_reqbufs handler in 
driver
> @@ -484,6 +530,7 @@ int vb2_reqbufs(struct vb2_queue *q, struct
> v4l2_requestbuffers *req) }
> 
>  	if (req->memory != V4L2_MEMORY_MMAP
> +			&& req->memory != V4L2_MEMORY_DMABUF
>  			&& req->memory != V4L2_MEMORY_USERPTR) {
>  		dprintk(1, "reqbufs: unsupported memory type\n");
>  		return -EINVAL;
> @@ -513,6 +560,11 @@ int vb2_reqbufs(struct vb2_queue *q, struct
> v4l2_requestbuffers *req) return -EINVAL;
>  	}
> 
> +	if (req->memory == V4L2_MEMORY_DMABUF && __verify_dmabuf_ops(q)) {
> +		dprintk(1, "reqbufs: DMABUF for current setup unsupported\n");
> +		return -EINVAL;
> +	}
> +
>  	if (req->count == 0 || q->num_buffers != 0 || q->memory != req->memory) {
>  		/*
>  		 * We already have buffers allocated, so first check if they
> @@ -620,7 +672,8 @@ int vb2_create_bufs(struct vb2_queue *q, struct
> v4l2_create_buffers *create) }
> 
>  	if (create->memory != V4L2_MEMORY_MMAP
> -			&& create->memory != V4L2_MEMORY_USERPTR) {
> +			&& create->memory != V4L2_MEMORY_USERPTR
> +			&& create->memory != V4L2_MEMORY_DMABUF) {
>  		dprintk(1, "%s(): unsupported memory type\n", __func__);
>  		return -EINVAL;
>  	}
> @@ -644,6 +697,11 @@ int vb2_create_bufs(struct vb2_queue *q, struct
> v4l2_create_buffers *create) return -EINVAL;
>  	}
> 
> +	if (create->memory == V4L2_MEMORY_DMABUF && __verify_dmabuf_ops(q)) {
> +		dprintk(1, "%s(): DMABUF for current setup unsupported\n", __func__);
> +		return -EINVAL;
> +	}
> +
>  	if (q->num_buffers == VIDEO_MAX_FRAME) {
>  		dprintk(1, "%s(): maximum number of buffers already allocated\n",
>  			__func__);
> @@ -839,6 +897,14 @@ static int __fill_vb2_buffer(struct vb2_buffer *vb,
> const struct v4l2_buffer *b, b->m.planes[plane].length;
>  			}
>  		}
> +		if (b->memory == V4L2_MEMORY_DMABUF) {
> +			for (plane = 0; plane < vb->num_planes; ++plane) {
> +				v4l2_planes[plane].bytesused =
> +					b->m.planes[plane].bytesused;
> +				v4l2_planes[plane].m.fd =
> +					b->m.planes[plane].m.fd;
> +			}
> +		}
>  	} else {
>  		/*
>  		 * Single-planar buffers do not use planes array,
> @@ -853,6 +919,10 @@ static int __fill_vb2_buffer(struct vb2_buffer *vb,
> const struct v4l2_buffer *b, v4l2_planes[0].m.userptr = b->m.userptr;
>  			v4l2_planes[0].length = b->length;
>  		}
> +
> +		if (b->memory == V4L2_MEMORY_DMABUF)
> +			v4l2_planes[0].m.fd = b->m.fd;
> +
>  	}
> 
>  	vb->v4l2_buf.field = b->field;
> @@ -957,6 +1027,105 @@ 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 = -EINVAL;
> +			goto err;
> +		}
> +
> +		/* Skip the plane if already verified */
> +		if (dbuf == vb->planes[plane].dbuf) {
> +			planes[plane].length = dbuf->size;
> +			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, 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 = call_memop(q, attach_dmabuf, q->alloc_ctx[plane],
> +			dbuf, q->plane_sizes[plane], write);
> +		if (IS_ERR(mem_priv)) {
> +			dprintk(1, "qbuf: failed acquiring dmabuf "
> +				"memory for plane %d\n", plane);
> +			ret = PTR_ERR(mem_priv);
> +			goto err;
> +		}
> +
> +		planes[plane].length = dbuf->size;
> +		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 = call_memop(q, map_dmabuf, vb->planes[plane].mem_priv);
> +		if (ret) {
> +			dprintk(1, "qbuf: failed mapping dmabuf "
> +				"memory for plane %d\n", plane);
> +			goto err;
> +		}
> +	}
> +
> +	/*
> +	 * 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)
> @@ -980,6 +1149,9 @@ 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;
> @@ -1312,6 +1484,7 @@ 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");
> @@ -1335,6 +1508,15 @@ 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

Typo.

> +	 * buffer is dequeued..
> +	 */
> +	if (q->memory == V4L2_MEMORY_DMABUF)
> +		for (plane = 0; plane < vb->num_planes; ++plane)
> +			call_memop(q, unmap_dmabuf,
> +				vb->planes[plane].mem_priv);
> +
>  	switch (vb->state) {
>  	case VB2_BUF_STATE_DONE:
>  		dprintk(3, "dqbuf: Returning done buffer\n");
> diff --git a/include/media/videobuf2-core.h
> b/include/media/videobuf2-core.h index a15d1f1..665e846 100644
> --- a/include/media/videobuf2-core.h
> +++ b/include/media/videobuf2-core.h
> @@ -16,6 +16,7 @@
>  #include <linux/mutex.h>
>  #include <linux/poll.h>
>  #include <linux/videodev2.h>
> +#include <linux/dma-buf.h>
> 
>  struct vb2_alloc_ctx;
>  struct vb2_fileio_data;
> @@ -41,6 +42,20 @@ struct vb2_fileio_data;
>   *		 argument to other ops in this structure
>   * @put_userptr: inform the allocator that a USERPTR buffer will no longer
>   *		 be used
> + * @attach_dmabuf: attach a shared struct dma_buf for a hardware
> operation; + *		   used for DMABUF memory types; alloc_ctx is the 
alloc
> context + *		   dbuf is the shared dma_buf; returns NULL on failure;
> + *		   allocator private per-buffer structure on success;
> + *		   this needs to be used for further accesses to the buffer
> + * @detach_dmabuf: inform the exporter of the buffer that the current
> DMABUF + *		   buffer is no longer used; the buf_priv argument is the
> + *		   allocator private per-buffer structure previously returned
> + *		   from the attach_dmabuf callback
> + * @map_dmabuf: request for access to the dmabuf from allocator; the
> allocator + *		of dmabuf is informed that this driver is going to use 
the
> + *		dmabuf
> + * @unmap_dmabuf: releases access control to the dmabuf - allocator is
> notified + *		  that this driver is done using the dmabuf for now
>   * @vaddr:	return a kernel virtual address to a given memory buffer
>   *		associated with the passed private structure or NULL if no
>   *		such mapping exists
> @@ -56,6 +71,8 @@ struct vb2_fileio_data;
>   * Required ops for USERPTR types: get_userptr, put_userptr.
>   * Required ops for MMAP types: alloc, put, num_users, mmap.
>   * Required ops for read/write access types: alloc, put, num_users, vaddr
> + * Required ops for DMABUF types: attach_dmabuf, detach_dmabuf,
> map_dmabuf, + *				  unmap_dmabuf.
>   */
>  struct vb2_mem_ops {
>  	void		*(*alloc)(void *alloc_ctx, unsigned long size);
> @@ -65,6 +82,17 @@ struct vb2_mem_ops {
>  					unsigned long size, int write);
>  	void		(*put_userptr)(void *buf_priv);
> 
> +	/*
> +	 * Comment from Rob Clark: XXX: I think the attach / detach could be
> +	 * handled in the vb2 core, and vb2_mem_ops really just need to get/put
> +	 * the sglist (and make sure that the sglist fits it's needs..)
> +	 */
> +	void		*(*attach_dmabuf)(void *alloc_ctx, struct dma_buf *dbuf,
> +				unsigned long size, int write);
> +	void		(*detach_dmabuf)(void *buf_priv);
> +	int		(*map_dmabuf)(void *buf_priv);
> +	void		(*unmap_dmabuf)(void *buf_priv);
> +
>  	void		*(*vaddr)(void *buf_priv);
>  	void		*(*cookie)(void *buf_priv);
> 
> @@ -75,6 +103,7 @@ struct vb2_mem_ops {
> 
>  struct vb2_plane {
>  	void			*mem_priv;
> +	struct dma_buf		*dbuf;
>  };
> 
>  /**
> @@ -83,12 +112,14 @@ struct vb2_plane {
>   * @VB2_USERPTR:	driver supports USERPTR with streaming API
>   * @VB2_READ:		driver supports read() style access
>   * @VB2_WRITE:		driver supports write() style access
> + * @VB2_DMABUF:		driver supports DMABUF with streaming API
>   */
>  enum vb2_io_modes {
>  	VB2_MMAP	= (1 << 0),
>  	VB2_USERPTR	= (1 << 1),
>  	VB2_READ	= (1 << 2),
>  	VB2_WRITE	= (1 << 3),
> +	VB2_DMABUF	= (1 << 4),
>  };
> 
>  /**


-- 
Rémi Denis-Courmont
http://www.remlab.net/
http://fi.linkedin.com/in/remidenis