Re: [PATCH 4/6 v4] V4L: vb2: add support for buffers of different sizes on a single queue

[Sakari Ailus <sakari.ailus@iki.fi>]

Hi Guennadi,

Thanks for the patch. I have a few comments below.

Guennadi Liakhovetski wrote:
> The two recently added ioctl()s VIDIOC_CREATE_BUFS and VIDIOC_PREPARE_BUF
> allow user-space applications to allocate video buffers of different
> sizes and hand them over to the driver for fast switching between
> different frame formats. This patch adds support for buffers of different
> sizes on the same buffer-queue to vb2.
> 
> Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
> ---
>  drivers/media/video/videobuf2-core.c |  266 +++++++++++++++++++++++++++++-----
>  include/media/videobuf2-core.h       |   31 +++--
>  2 files changed, 246 insertions(+), 51 deletions(-)
> 
> diff --git a/drivers/media/video/videobuf2-core.c b/drivers/media/video/videobuf2-core.c
> index 7045d1f..6e7f9e5 100644
> --- a/drivers/media/video/videobuf2-core.c
> +++ b/drivers/media/video/videobuf2-core.c
> @@ -44,7 +44,7 @@ module_param(debug, int, 0644);
>   * __vb2_buf_mem_alloc() - allocate video memory for the given buffer
>   */
>  static int __vb2_buf_mem_alloc(struct vb2_buffer *vb,
> -				unsigned int *plane_sizes)
> +				const unsigned int *plane_sizes)
>  {
>  	struct vb2_queue *q = vb->vb2_queue;
>  	void *mem_priv;
> @@ -110,13 +110,22 @@ static void __vb2_buf_userptr_put(struct vb2_buffer *vb)
>   * __setup_offsets() - setup unique offsets ("cookies") for every plane in
>   * every buffer on the queue
>   */
> -static void __setup_offsets(struct vb2_queue *q)
> +static void __setup_offsets(struct vb2_queue *q, unsigned int n)
>  {
>  	unsigned int buffer, plane;
>  	struct vb2_buffer *vb;
> -	unsigned long off = 0;
> +	unsigned long off;
>  
> -	for (buffer = 0; buffer < q->num_buffers; ++buffer) {
> +	if (q->num_buffers) {
> +		struct v4l2_plane *p;
> +		vb = q->bufs[q->num_buffers - 1];
> +		p = &vb->v4l2_planes[vb->num_planes - 1];
> +		off = PAGE_ALIGN(p->m.mem_offset + p->length);
> +	} else {
> +		off = 0;
> +	}
> +
> +	for (buffer = q->num_buffers; buffer < q->num_buffers + n; ++buffer) {
>  		vb = q->bufs[buffer];
>  		if (!vb)
>  			continue;
> @@ -142,7 +151,7 @@ static void __setup_offsets(struct vb2_queue *q)
>   */
>  static int __vb2_queue_alloc(struct vb2_queue *q, enum v4l2_memory memory,
>  			     unsigned int num_buffers, unsigned int num_planes,
> -			     unsigned int plane_sizes[])
> +			     const unsigned int *plane_sizes)
>  {
>  	unsigned int buffer;
>  	struct vb2_buffer *vb;
> @@ -163,7 +172,7 @@ static int __vb2_queue_alloc(struct vb2_queue *q, enum v4l2_memory memory,
>  		vb->state = VB2_BUF_STATE_DEQUEUED;
>  		vb->vb2_queue = q;
>  		vb->num_planes = num_planes;
> -		vb->v4l2_buf.index = buffer;
> +		vb->v4l2_buf.index = q->num_buffers + buffer;
>  		vb->v4l2_buf.type = q->type;
>  		vb->v4l2_buf.memory = memory;
>  
> @@ -191,15 +200,13 @@ static int __vb2_queue_alloc(struct vb2_queue *q, enum v4l2_memory memory,
>  			}
>  		}
>  
> -		q->bufs[buffer] = vb;
> +		q->bufs[q->num_buffers + buffer] = vb;
>  	}
>  
> -	q->num_buffers = buffer;
> -
> -	__setup_offsets(q);
> +	__setup_offsets(q, buffer);
>  
>  	dprintk(1, "Allocated %d buffers, %d plane(s) each\n",
> -			q->num_buffers, num_planes);
> +			buffer, num_planes);
>  
>  	return buffer;
>  }
> @@ -207,12 +214,13 @@ static int __vb2_queue_alloc(struct vb2_queue *q, enum v4l2_memory memory,
>  /**
>   * __vb2_free_mem() - release all video buffer memory for a given queue
>   */
> -static void __vb2_free_mem(struct vb2_queue *q)
> +static void __vb2_free_mem(struct vb2_queue *q, unsigned int buffers)
>  {
>  	unsigned int buffer;
>  	struct vb2_buffer *vb;
>  
> -	for (buffer = 0; buffer < q->num_buffers; ++buffer) {
> +	for (buffer = q->num_buffers - buffers; buffer < q->num_buffers;
> +	     ++buffer) {
>  		vb = q->bufs[buffer];
>  		if (!vb)
>  			continue;
> @@ -226,17 +234,18 @@ static void __vb2_free_mem(struct vb2_queue *q)
>  }
>  
>  /**
> - * __vb2_queue_free() - free the queue - video memory and related information
> - * and return the queue to an uninitialized state. Might be called even if the
> - * queue has already been freed.
> + * __vb2_queue_free() - free buffers at the end of the queue - video memory and
> + * related information, if no buffers are left return the queue to an
> + * uninitialized state. Might be called even if the queue has already been freed.
>   */
> -static void __vb2_queue_free(struct vb2_queue *q)
> +static void __vb2_queue_free(struct vb2_queue *q, unsigned int buffers)
>  {
>  	unsigned int buffer;
>  
>  	/* Call driver-provided cleanup function for each buffer, if provided */
>  	if (q->ops->buf_cleanup) {
> -		for (buffer = 0; buffer < q->num_buffers; ++buffer) {
> +		for (buffer = q->num_buffers - buffers; buffer < q->num_buffers;
> +		     ++buffer) {
>  			if (NULL == q->bufs[buffer])
>  				continue;
>  			q->ops->buf_cleanup(q->bufs[buffer]);
> @@ -244,16 +253,18 @@ static void __vb2_queue_free(struct vb2_queue *q)
>  	}
>  
>  	/* Release video buffer memory */
> -	__vb2_free_mem(q);
> +	__vb2_free_mem(q, buffers);
>  
>  	/* Free videobuf buffers */
> -	for (buffer = 0; buffer < q->num_buffers; ++buffer) {
> +	for (buffer = q->num_buffers - buffers; buffer < q->num_buffers;
> +	     ++buffer) {
>  		kfree(q->bufs[buffer]);
>  		q->bufs[buffer] = NULL;
>  	}
>  
> -	q->num_buffers = 0;
> -	q->memory = 0;
> +	q->num_buffers -= buffers;
> +	if (!q->num_buffers)
> +		q->memory = 0;
>  }
>  
>  /**
> @@ -454,7 +465,7 @@ static bool __buffers_in_use(struct vb2_queue *q)
>   */
>  int vb2_reqbufs(struct vb2_queue *q, struct v4l2_requestbuffers *req)
>  {
> -	unsigned int num_buffers, num_planes;
> +	unsigned int num_buffers, allocated_buffers, num_planes = 0;
>  	unsigned int plane_sizes[VIDEO_MAX_PLANES];
>  	int ret = 0;
>  
> @@ -503,7 +514,7 @@ int vb2_reqbufs(struct vb2_queue *q, struct v4l2_requestbuffers *req)
>  			return -EBUSY;
>  		}
>  
> -		__vb2_queue_free(q);
> +		__vb2_queue_free(q, q->num_buffers);
>  
>  		/*
>  		 * In case of REQBUFS(0) return immediately without calling
> @@ -538,44 +549,166 @@ int vb2_reqbufs(struct vb2_queue *q, struct v4l2_requestbuffers *req)
>  		return -ENOMEM;
>  	}
>  
> +	allocated_buffers = ret;
> +
>  	/*
>  	 * Check if driver can handle the allocated number of buffers.
>  	 */
>  	if (ret < num_buffers) {
> -		unsigned int orig_num_buffers;
> +		num_buffers = ret;
>  
> -		orig_num_buffers = num_buffers = ret;
>  		ret = call_qop(q, queue_setup, q, &num_buffers, &num_planes,
>  			       plane_sizes, q->alloc_ctx);
> -		if (ret)
> -			goto free_mem;
>  
> -		if (orig_num_buffers < num_buffers) {
> +		if (!ret && allocated_buffers < num_buffers)
>  			ret = -ENOMEM;
> -			goto free_mem;
> -		}
>  
>  		/*
> -		 * Ok, driver accepted smaller number of buffers.
> +		 * Either the driver has accepted a smaller number of buffers,
> +		 * or .queue_setup() returned an error
>  		 */
> -		ret = num_buffers;
> +	}
> +
> +	q->num_buffers = allocated_buffers;
> +
> +	if (ret < 0) {
> +		__vb2_queue_free(q, allocated_buffers);
> +		return ret;
>  	}
>  
>  	/*
>  	 * Return the number of successfully allocated buffers
>  	 * to the userspace.
>  	 */
> -	req->count = ret;
> +	req->count = allocated_buffers;
>  
>  	return 0;
> -
> -free_mem:
> -	__vb2_queue_free(q);
> -	return ret;
>  }
>  EXPORT_SYMBOL_GPL(vb2_reqbufs);
>  
>  /**
> + * vb2_create_bufs() - Allocate buffers and any required auxiliary structs
> + * @q:		videobuf2 queue
> + * @create:	creation parameters, passed from userspace to vidioc_create_bufs
> + *		handler in driver
> + *
> + * Should be called from vidioc_create_bufs ioctl handler of a driver.
> + * This function:
> + * 1) verifies parameter sanity
> + * 2) calls the .queue_setup() queue operation
> + * 3) performs any necessary memory allocations
> + *
> + * The return values from this function are intended to be directly returned
> + * from vidioc_create_bufs handler in driver.
> + */
> +int vb2_create_bufs(struct vb2_queue *q, struct v4l2_create_buffers *create)
> +{
> +	unsigned int num_planes = create->num_planes,
> +		num_buffers = create->count, allocated_buffers;
> +	int ret = 0;
> +
> +	if (q->fileio) {
> +		dprintk(1, "%s(): file io in progress\n", __func__);
> +		return -EBUSY;
> +	}
> +
> +	if (create->memory != V4L2_MEMORY_MMAP
> +			&& create->memory != V4L2_MEMORY_USERPTR) {
> +		dprintk(1, "%s(): unsupported memory type\n", __func__);
> +		return -EINVAL;
> +	}
> +
> +	if (create->type != q->type) {
> +		dprintk(1, "%s(): requested type is incorrect\n", __func__);
> +		return -EINVAL;
> +	}
> +
> +	/*
> +	 * Make sure all the required memory ops for given memory type
> +	 * are available.
> +	 */
> +	if (create->memory == V4L2_MEMORY_MMAP && __verify_mmap_ops(q)) {
> +		dprintk(1, "%s(): MMAP for current setup unsupported\n", __func__);
> +		return -EINVAL;
> +	}
> +
> +	if (create->memory == V4L2_MEMORY_USERPTR && __verify_userptr_ops(q)) {
> +		dprintk(1, "%s(): USERPTR 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__);
> +		return -ENOBUFS;
> +	}
> +
> +	create->index = q->num_buffers;
> +
> +	if (!q->num_buffers) {
> +		memset(q->alloc_ctx, 0, sizeof(q->alloc_ctx));
> +		q->memory = create->memory;
> +	}
> +
> +	/*
> +	 * Ask the driver, whether the requested number of buffers, planes per
> +	 * buffer and their sizes are acceptable
> +	 */
> +	ret = call_qop(q, queue_setup, q, &num_buffers, &num_planes,
> +		       create->sizes, q->alloc_ctx);
> +	if (ret)
> +		return ret;
> +
> +	/* Finally, allocate buffers and video memory */
> +	ret = __vb2_queue_alloc(q, create->memory, num_buffers,
> +				num_planes, create->sizes);
> +	if (ret < 0) {
> +		dprintk(1, "Memory allocation failed with error: %d\n", ret);
> +		return ret;
> +	}
> +
> +	allocated_buffers = ret;
> +
> +	/*
> +	 * Check if driver can handle the so far allocated number of buffers.
> +	 */
> +	if (ret < num_buffers) {
> +		num_buffers = ret;

s/ret/allocated_buffers/ might make the above easier to understand.

> +
> +		/*
> +		 * q->num_buffers contains the total number of buffers, that the
> +		 * queue driver has set up
> +		 */
> +		ret = call_qop(q, queue_setup, q, &num_buffers,
> +			       &num_planes, create->sizes, q->alloc_ctx);
> +
> +		if (!ret && allocated_buffers < num_buffers)
> +			ret = -ENOMEM;

Is this really an error? How is the queue_setup op expected to change
num_buffers, and why?

> +
> +		/*
> +		 * Either the driver has accepted a smaller number of buffers,
> +		 * or .queue_setup() returned an error
> +		 */
> +	}
> +
> +	q->num_buffers += allocated_buffers;
> +
> +	if (ret < 0) {
> +		__vb2_queue_free(q, allocated_buffers);
> +		return ret;
> +	}
> +
> +	/*
> +	 * Return the number of successfully allocated buffers
> +	 * to the userspace.
> +	 */
> +	create->count = allocated_buffers;
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(vb2_create_bufs);
> +
> +/**
>   * vb2_plane_vaddr() - Return a kernel virtual address of a given plane
>   * @vb:		vb2_buffer to which the plane in question belongs to
>   * @plane_no:	plane number for which the address is to be returned
> @@ -844,6 +977,61 @@ static int __buf_prepare(struct vb2_buffer *vb, struct v4l2_buffer *b)
>  }
>  
>  /**
> + * vb2_prepare_buf() - Pass ownership of a buffer from userspace to the kernel
> + * @q:		videobuf2 queue
> + * @b:		buffer structure passed from userspace to vidioc_prepare_buf
> + *		handler in driver
> + *
> + * Should be called from vidioc_prepare_buf ioctl handler of a driver.
> + * This function:
> + * 1) verifies the passed buffer,
> + * 2) calls buf_prepare callback in the driver (if provided), in which
> + *    driver-specific buffer initialization can be performed,
> + *
> + * The return values from this function are intended to be directly returned
> + * from vidioc_prepare_buf handler in driver.
> + */
> +int vb2_prepare_buf(struct vb2_queue *q, struct v4l2_buffer *b)
> +{
> +	struct vb2_buffer *vb;
> +
> +	if (q->fileio) {
> +		dprintk(1, "%s(): file io in progress\n", __func__);
> +		return -EBUSY;
> +	}
> +
> +	if (b->type != q->type) {
> +		dprintk(1, "%s(): invalid buffer type\n", __func__);
> +		return -EINVAL;
> +	}
> +
> +	if (b->index >= q->num_buffers) {
> +		dprintk(1, "%s(): buffer index out of range\n", __func__);
> +		return -EINVAL;
> +	}
> +
> +	vb = q->bufs[b->index];
> +	if (NULL == vb) {
> +		/* Should never happen */
> +		dprintk(1, "%s(): buffer is NULL\n", __func__);
> +		return -EINVAL;
> +	}
> +
> +	if (b->memory != q->memory) {
> +		dprintk(1, "%s(): invalid memory type\n", __func__);
> +		return -EINVAL;
> +	}
> +
> +	if (vb->state != VB2_BUF_STATE_DEQUEUED) {
> +		dprintk(1, "%s(): invalid buffer state %d\n", __func__, vb->state);
> +		return -EINVAL;
> +	}
> +
> +	return __buf_prepare(vb, b);
> +}
> +EXPORT_SYMBOL_GPL(vb2_prepare_buf);
> +
> +/**
>   * vb2_qbuf() - Queue a buffer from userspace
>   * @q:		videobuf2 queue
>   * @b:		buffer structure passed from userspace to vidioc_qbuf handler
> @@ -1476,7 +1664,7 @@ void vb2_queue_release(struct vb2_queue *q)
>  {
>  	__vb2_cleanup_fileio(q);
>  	__vb2_queue_cancel(q);
> -	__vb2_queue_free(q);
> +	__vb2_queue_free(q, q->num_buffers);
>  }
>  EXPORT_SYMBOL_GPL(vb2_queue_release);
>  
> diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
> index 7dd6bca..8900e25 100644
> --- a/include/media/videobuf2-core.h
> +++ b/include/media/videobuf2-core.h
> @@ -172,13 +172,17 @@ struct vb2_buffer {
>  /**
>   * struct vb2_ops - driver-specific callbacks
>   *
> - * @queue_setup:	called from a VIDIOC_REQBUFS handler, before
> - *			memory allocation; driver should return the required
> - *			number of buffers in num_buffers, the required number
> - *			of planes per buffer in num_planes; the size of each
> - *			plane should be set in the sizes[] array and optional
> - *			per-plane allocator specific context in alloc_ctxs[]
> - *			array
> + * @queue_setup:	called from VIDIOC_REQBUFS and VIDIOC_CREATE_BUFS
> + *			handlers, before memory allocation. When called with
> + *			zeroed num_planes or plane sizes, the driver should
> + *			return the required number of buffers in num_buffers,
> + *			the required number of planes per buffer in num_planes;
> + *			the size of each plane should be set in the sizes[]
> + *			array and optional per-plane allocator specific context
> + *			in alloc_ctxs[] array. If num_planes and sizes[] are
> + *			both non-zero, the driver should use them. Otherwise the
> + *			driver must make no assumptions about the buffers, that
> + *			will be made available to it.
>   * @wait_prepare:	release any locks taken while calling vb2 functions;
>   *			it is called before an ioctl needs to wait for a new
>   *			buffer to arrive; required to avoid a deadlock in
> @@ -191,11 +195,11 @@ struct vb2_buffer {
>   *			perform additional buffer-related initialization;
>   *			initialization failure (return != 0) will prevent
>   *			queue setup from completing successfully; optional
> - * @buf_prepare:	called every time the buffer is queued from userspace;
> - *			drivers may perform any initialization required before
> - *			each hardware operation in this callback;
> - *			if an error is returned, the buffer will not be queued
> - *			in driver; optional
> + * @buf_prepare:	called every time the buffer is queued from userspace
> + *			and from the VIDIOC_PREPARE_BUF ioctl; drivers may
> + *			perform any initialization required before each hardware
> + *			operation in this callback; if an error is returned, the
> + *			buffer will not be queued in driver; optional
>   * @buf_finish:		called before every dequeue of the buffer back to
>   *			userspace; drivers may perform any operations required
>   *			before userspace accesses the buffer; optional
> @@ -293,6 +297,9 @@ int vb2_wait_for_all_buffers(struct vb2_queue *q);
>  int vb2_querybuf(struct vb2_queue *q, struct v4l2_buffer *b);
>  int vb2_reqbufs(struct vb2_queue *q, struct v4l2_requestbuffers *req);
>  
> +int vb2_create_bufs(struct vb2_queue *q, struct v4l2_create_buffers *create);
> +int vb2_prepare_buf(struct vb2_queue *q, struct v4l2_buffer *b);
> +
>  int vb2_queue_init(struct vb2_queue *q);
>  
>  void vb2_queue_release(struct vb2_queue *q);


-- 
Sakari Ailus
sakari.ailus@iki.fi