Re: [PATCH v21 7/9] media: v4l2: Add REMOVE_BUFS ioctl

[Mauro Carvalho Chehab <mchehab@kernel.org>]

Em Thu, 21 Mar 2024 15:24:43 +0100
Hans Verkuil <hverkuil-cisco@xs4all.nl> escreveu:

> On 21/03/2024 3:14 pm, Mauro Carvalho Chehab wrote:
> > Em Thu, 14 Mar 2024 16:32:24 +0100
> > Benjamin Gaignard <benjamin.gaignard@collabora.com> escreveu:
> >   
> >> VIDIOC_REMOVE_BUFS ioctl allows to remove buffers from a queue.
> >> The number of buffers to remove in given by count field of
> >> struct v4l2_remove_buffers and the range start at the index
> >> specified in the same structure.
> >>
> >> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@collabora.com>
> >> ---
> >> changes in version 21:
> >> - Be more careful about checking remove_bufs type field vs queue type.
> >> - Add documentation about type checking error.
> >> - Always set capabilities flags field.
> >>
> >>  .../userspace-api/media/v4l/user-func.rst     |  1 +
> >>  .../media/v4l/vidioc-remove-bufs.rst          | 85 +++++++++++++++++++
> >>  .../media/v4l/vidioc-reqbufs.rst              |  1 +
> >>  .../media/common/videobuf2/videobuf2-core.c   | 38 +++++++++
> >>  .../media/common/videobuf2/videobuf2-v4l2.c   | 20 ++++-
> >>  drivers/media/v4l2-core/v4l2-dev.c            |  3 +
> >>  drivers/media/v4l2-core/v4l2-ioctl.c          | 30 +++++++
> >>  include/media/v4l2-ioctl.h                    |  4 +
> >>  include/media/videobuf2-core.h                | 10 +++
> >>  include/media/videobuf2-v4l2.h                |  2 +
> >>  include/uapi/linux/videodev2.h                | 17 ++++
> >>  11 files changed, 210 insertions(+), 1 deletion(-)
> >>  create mode 100644 Documentation/userspace-api/media/v4l/vidioc-remove-bufs.rst
> >>
> >> diff --git a/Documentation/userspace-api/media/v4l/user-func.rst b/Documentation/userspace-api/media/v4l/user-func.rst
> >> index 15ff0bf7bbe6..6f661138801c 100644
> >> --- a/Documentation/userspace-api/media/v4l/user-func.rst
> >> +++ b/Documentation/userspace-api/media/v4l/user-func.rst
> >> @@ -62,6 +62,7 @@ Function Reference
> >>      vidioc-query-dv-timings
> >>      vidioc-querystd
> >>      vidioc-reqbufs
> >> +    vidioc-remove-bufs
> >>      vidioc-s-hw-freq-seek
> >>      vidioc-streamon
> >>      vidioc-subdev-enum-frame-interval
> >> diff --git a/Documentation/userspace-api/media/v4l/vidioc-remove-bufs.rst b/Documentation/userspace-api/media/v4l/vidioc-remove-bufs.rst
> >> new file mode 100644
> >> index 000000000000..0cbc8c7313b7
> >> --- /dev/null
> >> +++ b/Documentation/userspace-api/media/v4l/vidioc-remove-bufs.rst
> >> @@ -0,0 +1,85 @@
> >> +.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
> >> +.. c:namespace:: V4L
> >> +
> >> +.. _VIDIOC_REMOVE_BUFS:
> >> +
> >> +************************
> >> +ioctl VIDIOC_REMOVE_BUFS
> >> +************************
> >> +
> >> +Name
> >> +====
> >> +
> >> +VIDIOC_REMOVE_BUFS - Removes buffers from a queue
> >> +
> >> +Synopsis
> >> +========
> >> +
> >> +.. c:macro:: VIDIOC_REMOVE_BUFS
> >> +
> >> +``int ioctl(int fd, VIDIOC_REMOVE_BUFS, struct v4l2_remove_buffers *argp)``
> >> +
> >> +Arguments
> >> +=========
> >> +
> >> +``fd``
> >> +    File descriptor returned by :c:func:`open()`.
> >> +
> >> +``argp``
> >> +    Pointer to struct :c:type:`v4l2_remove_buffers`.
> >> +
> >> +Description
> >> +===========
> >> +
> >> +Applications can optionally call the :ref:`VIDIOC_REMOVE_BUFS` ioctl to
> >> +remove buffers from a queue.
> >> +:ref:`VIDIOC_CREATE_BUFS` ioctl support is mandatory to enable :ref:`VIDIOC_REMOVE_BUFS`.
> >> +This ioctl is available if the ``V4L2_BUF_CAP_SUPPORTS_REMOVE_BUFS`` capability
> >> +is set on the queue when :c:func:`VIDIOC_REQBUFS` or :c:func:`VIDIOC_CREATE_BUFS`
> >> +are invoked.
> >> +
> >> +.. c:type:: v4l2_remove_buffers
> >> +
> >> +.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.5cm}|
> >> +
> >> +.. flat-table:: struct v4l2_remove_buffers
> >> +    :header-rows:  0
> >> +    :stub-columns: 0
> >> +    :widths:       1 1 2
> >> +
> >> +    * - __u32
> >> +      - ``index``
> >> +      - The starting buffer index to remove. This field is ignored if count == 0.
> >> +    * - __u32
> >> +      - ``count``
> >> +      - The number of buffers to be removed with indices 'index' until 'index + count - 1'.
> >> +        All buffers in this range must be valid and in DEQUEUED state.
> >> +        :ref:`VIDIOC_REMOVE_BUFS` will always check the validity of ``type`, if it is
> >> +        invalid it returns ``EINVAL`` error code.
> >> +        If count is set to 0 :ref:`VIDIOC_REMOVE_BUFS` will do nothing and return 0.
> >> +    * - __u32
> >> +      - ``type``
> >> +      - Type of the stream or buffers, this is the same as the struct
> >> +	:c:type:`v4l2_format` ``type`` field. See
> >> +	:c:type:`v4l2_buf_type` for valid values.
> >> +    * - __u32
> >> +      - ``reserved``\ [13]
> >> +      - A place holder for future extensions. Drivers and applications
> >> +	must set the array to zero.
> >> +
> >> +Return Value
> >> +============
> >> +
> >> +On success 0 is returned, on error -1 and the ``errno`` variable is set
> >> +appropriately. The generic error codes are described at the
> >> +:ref:`Generic Error Codes <gen-errors>` chapter.  
> > 
> > It is not enough to just return an error code. it should also describe
> > what will be the expected behavior after the call. Something like:
> > 
> > 	If an error occurs, no buffers will be freed and one of the
> > 	error codes below will be returned:  
> 
> That's good to have. That is indeed not stated explicitly.
> 
> >   
> >> +
> >> +EBUSY
> >> +    File I/O is in progress.
> >> +    One or more of the buffers in the range ``index`` to ``index + count - 1`` are not
> >> +    in DEQUEUED state.
> >> +
> >> +EINVAL
> >> +    One or more of the buffers in the range ``index`` to ``index + count - 1`` do not
> >> +    exist in the queue.
> >> +    The buffer type (``type`` field) is not valid.  
> > 
> > IMO, it needs also another error code: as there's a minimal number of
> > buffers to be queued (let's say, 2), what happens if there are currently
> > 3 buffers allocated and an ioctl is called to free 2 buffers?
> > 
> > IMO, it shall return an error code and not free any buffers.  
> 
> Note the requirement that all buffers you want to remove have to be in dequeued
> state. So you can never remove buffers that are still in flight. An attempt to
> do that results in EBUSY.
> 
> So there is no need for an other error code.
> 
> > 
> > The best would be to return a code different than EINVAL. Maybe E2BIG?
> >   
> >> diff --git a/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst b/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst
> >> index 0b3a41a45d05..bbc22dd76032 100644
> >> --- a/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst
> >> +++ b/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst
> >> @@ -121,6 +121,7 @@ aborting or finishing any DMA in progress, an implicit
> >>  .. _V4L2-BUF-CAP-SUPPORTS-M2M-HOLD-CAPTURE-BUF:
> >>  .. _V4L2-BUF-CAP-SUPPORTS-MMAP-CACHE-HINTS:
> >>  .. _V4L2-BUF-CAP-SUPPORTS-MAX-NUM-BUFFERS:
> >> +.. _V4L2-BUF-CAP-SUPPORTS-REMOVE-BUFS:
> >>  
> >>  .. raw:: latex
> >>  
> >> diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c
> >> index 009cea95d662..0b2b48e1b2df 100644
> >> --- a/drivers/media/common/videobuf2/videobuf2-core.c
> >> +++ b/drivers/media/common/videobuf2/videobuf2-core.c
> >> @@ -1691,6 +1691,44 @@ int vb2_core_prepare_buf(struct vb2_queue *q, struct vb2_buffer *vb, void *pb)
> >>  }
> >>  EXPORT_SYMBOL_GPL(vb2_core_prepare_buf);
> >>  
> >> +int vb2_core_remove_bufs(struct vb2_queue *q, unsigned int start, unsigned int count)
> >> +{
> >> +	unsigned int i, ret = 0;
> >> +	unsigned int q_num_bufs = vb2_get_num_buffers(q);
> >> +
> >> +	if (count == 0)
> >> +		return 0;
> >> +
> >> +	if (count > q_num_bufs)
> >> +		return -EINVAL;  
> > 
> > It also needs:
> > 
> > 	if (q_num_bufs - count < q->min_reqbufs_allocation && q_num_bufs != count)
> > 		return <some error code>;
> > 
> > e. g. it shall not accept keeping, for instance, just one buffer allocated.  
> 
> That's perfectly fine. The min_reqbufs_allocation is specific to VIDIOC_REQBUFS
> (hence the name). If you use CREATE_BUFS/REMOVE_BUFS, then you are fully responsible
> for allocating and removing buffers.
> 
> This is something that was discussed in earlier revisions of this series.
> 
> It is actually rather ugly that REQBUFS does this, but we need to keep that behavior
> since that's how REQBUFS worked historically.
> 
> VIDIOC_CREATE_BUFS was never affected by this, so if you want to allocate N
> buffers with CREATE_BUFS, then you'll never get more than N buffers (you might get
> less, of course).

OK.

So, after doing the documentation change, feel free to add:

Reviewed-by: Mauro Carvalho Chehab <mchehab@kernel.org>

> 
> Regards,
> 
> 	Hans
> 
> >   
> >> +
> >> +	if (start > q->max_num_buffers - count)
> >> +		return -EINVAL;
> >> +
> >> +	mutex_lock(&q->mmap_lock);
> >> +
> >> +	/* Check that all buffers in the range exist */
> >> +	for (i = start; i < start + count; i++) {
> >> +		struct vb2_buffer *vb = vb2_get_buffer(q, i);
> >> +
> >> +		if (!vb) {
> >> +			ret = -EINVAL;
> >> +			goto unlock;
> >> +		}
> >> +		if (vb->state != VB2_BUF_STATE_DEQUEUED) {
> >> +			ret = -EBUSY;
> >> +			goto unlock;
> >> +		}
> >> +	}
> >> +	__vb2_queue_free(q, start, count);
> >> +	dprintk(q, 2, "%u buffers removed\n", count);
> >> +
> >> +unlock:
> >> +	mutex_unlock(&q->mmap_lock);
> >> +	return ret;
> >> +}
> >> +EXPORT_SYMBOL_GPL(vb2_core_remove_bufs);
> >> +
> >>  /*
> >>   * vb2_start_streaming() - Attempt to start streaming.
> >>   * @q:		videobuf2 queue
> >> diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c b/drivers/media/common/videobuf2/videobuf2-v4l2.c
> >> index 03e8080a68a8..293f3d5f1c4e 100644
> >> --- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
> >> +++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
> >> @@ -685,7 +685,7 @@ static void vb2_set_flags_and_caps(struct vb2_queue *q, u32 memory,
> >>  		*flags &= V4L2_MEMORY_FLAG_NON_COHERENT;
> >>  	}
> >>  
> >> -	*caps = V4L2_BUF_CAP_SUPPORTS_ORPHANED_BUFS;
> >> +	*caps |= V4L2_BUF_CAP_SUPPORTS_ORPHANED_BUFS;
> >>  	if (q->io_modes & VB2_MMAP)
> >>  		*caps |= V4L2_BUF_CAP_SUPPORTS_MMAP;
> >>  	if (q->io_modes & VB2_USERPTR)
> >> @@ -1001,6 +1001,24 @@ EXPORT_SYMBOL_GPL(vb2_poll);
> >>  
> >>  /* vb2 ioctl helpers */
> >>  
> >> +int vb2_ioctl_remove_bufs(struct file *file, void *priv,
> >> +			  struct v4l2_remove_buffers *d)
> >> +{
> >> +	struct video_device *vdev = video_devdata(file);
> >> +
> >> +	if (vdev->queue->type != d->type)
> >> +		return -EINVAL;
> >> +
> >> +	if (d->count == 0)
> >> +		return 0;
> >> +
> >> +	if (vb2_queue_is_busy(vdev->queue, file))
> >> +		return -EBUSY;
> >> +
> >> +	return vb2_core_remove_bufs(vdev->queue, d->index, d->count);
> >> +}
> >> +EXPORT_SYMBOL_GPL(vb2_ioctl_remove_bufs);
> >> +
> >>  int vb2_ioctl_reqbufs(struct file *file, void *priv,
> >>  			  struct v4l2_requestbuffers *p)
> >>  {
> >> diff --git a/drivers/media/v4l2-core/v4l2-dev.c b/drivers/media/v4l2-core/v4l2-dev.c
> >> index d13954bd31fd..e39e9742fdb5 100644
> >> --- a/drivers/media/v4l2-core/v4l2-dev.c
> >> +++ b/drivers/media/v4l2-core/v4l2-dev.c
> >> @@ -722,6 +722,9 @@ static void determine_valid_ioctls(struct video_device *vdev)
> >>  		SET_VALID_IOCTL(ops, VIDIOC_PREPARE_BUF, vidioc_prepare_buf);
> >>  		SET_VALID_IOCTL(ops, VIDIOC_STREAMON, vidioc_streamon);
> >>  		SET_VALID_IOCTL(ops, VIDIOC_STREAMOFF, vidioc_streamoff);
> >> +		/* VIDIOC_CREATE_BUFS support is mandatory to enable VIDIOC_REMOVE_BUFS */
> >> +		if (ops->vidioc_create_bufs)
> >> +			SET_VALID_IOCTL(ops, VIDIOC_REMOVE_BUFS, vidioc_remove_bufs);
> >>  	}
> >>  
> >>  	if (is_vid || is_vbi || is_meta) {
> >> diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c
> >> index 6e7b8b682d13..5aeff5519407 100644
> >> --- a/drivers/media/v4l2-core/v4l2-ioctl.c
> >> +++ b/drivers/media/v4l2-core/v4l2-ioctl.c
> >> @@ -489,6 +489,14 @@ static void v4l_print_create_buffers(const void *arg, bool write_only)
> >>  	v4l_print_format(&p->format, write_only);
> >>  }
> >>  
> >> +static void v4l_print_remove_buffers(const void *arg, bool write_only)
> >> +{
> >> +	const struct v4l2_remove_buffers *p = arg;
> >> +
> >> +	pr_cont("type=%s, index=%u, count=%u\n",
> >> +		prt_names(p->type, v4l2_type_names), p->index, p->count);
> >> +}
> >> +
> >>  static void v4l_print_streamparm(const void *arg, bool write_only)
> >>  {
> >>  	const struct v4l2_streamparm *p = arg;
> >> @@ -2092,6 +2100,7 @@ static int v4l_overlay(const struct v4l2_ioctl_ops *ops,
> >>  static int v4l_reqbufs(const struct v4l2_ioctl_ops *ops,
> >>  				struct file *file, void *fh, void *arg)
> >>  {
> >> +	struct video_device *vfd = video_devdata(file);
> >>  	struct v4l2_requestbuffers *p = arg;
> >>  	int ret = check_fmt(file, p->type);
> >>  
> >> @@ -2100,6 +2109,10 @@ static int v4l_reqbufs(const struct v4l2_ioctl_ops *ops,
> >>  
> >>  	memset_after(p, 0, flags);
> >>  
> >> +	p->capabilities = 0;
> >> +	if (is_valid_ioctl(vfd, VIDIOC_REMOVE_BUFS))
> >> +		p->capabilities = V4L2_BUF_CAP_SUPPORTS_REMOVE_BUFS;
> >> +
> >>  	return ops->vidioc_reqbufs(file, fh, p);
> >>  }
> >>  
> >> @@ -2133,6 +2146,7 @@ static int v4l_dqbuf(const struct v4l2_ioctl_ops *ops,
> >>  static int v4l_create_bufs(const struct v4l2_ioctl_ops *ops,
> >>  				struct file *file, void *fh, void *arg)
> >>  {
> >> +	struct video_device *vfd = video_devdata(file);
> >>  	struct v4l2_create_buffers *create = arg;
> >>  	int ret = check_fmt(file, create->format.type);
> >>  
> >> @@ -2143,6 +2157,10 @@ static int v4l_create_bufs(const struct v4l2_ioctl_ops *ops,
> >>  
> >>  	v4l_sanitize_format(&create->format);
> >>  
> >> +	create->capabilities = 0;
> >> +	if (is_valid_ioctl(vfd, VIDIOC_REMOVE_BUFS))
> >> +		create->capabilities = V4L2_BUF_CAP_SUPPORTS_REMOVE_BUFS;
> >> +
> >>  	ret = ops->vidioc_create_bufs(file, fh, create);
> >>  
> >>  	if (create->format.type == V4L2_BUF_TYPE_VIDEO_CAPTURE ||
> >> @@ -2161,6 +2179,17 @@ static int v4l_prepare_buf(const struct v4l2_ioctl_ops *ops,
> >>  	return ret ? ret : ops->vidioc_prepare_buf(file, fh, b);
> >>  }
> >>  
> >> +static int v4l_remove_bufs(const struct v4l2_ioctl_ops *ops,
> >> +			   struct file *file, void *fh, void *arg)
> >> +{
> >> +	struct v4l2_remove_buffers *remove = arg;
> >> +
> >> +	if (ops->vidioc_remove_bufs)
> >> +		return ops->vidioc_remove_bufs(file, fh, remove);
> >> +
> >> +	return -ENOTTY;
> >> +}
> >> +
> >>  static int v4l_g_parm(const struct v4l2_ioctl_ops *ops,
> >>  				struct file *file, void *fh, void *arg)
> >>  {
> >> @@ -2910,6 +2939,7 @@ static const struct v4l2_ioctl_info v4l2_ioctls[] = {
> >>  	IOCTL_INFO(VIDIOC_ENUM_FREQ_BANDS, v4l_enum_freq_bands, v4l_print_freq_band, 0),
> >>  	IOCTL_INFO(VIDIOC_DBG_G_CHIP_INFO, v4l_dbg_g_chip_info, v4l_print_dbg_chip_info, INFO_FL_CLEAR(v4l2_dbg_chip_info, match)),
> >>  	IOCTL_INFO(VIDIOC_QUERY_EXT_CTRL, v4l_query_ext_ctrl, v4l_print_query_ext_ctrl, INFO_FL_CTRL | INFO_FL_CLEAR(v4l2_query_ext_ctrl, id)),
> >> +	IOCTL_INFO(VIDIOC_REMOVE_BUFS, v4l_remove_bufs, v4l_print_remove_buffers, INFO_FL_PRIO | INFO_FL_QUEUE | INFO_FL_CLEAR(v4l2_remove_buffers, type)),
> >>  };
> >>  #define V4L2_IOCTLS ARRAY_SIZE(v4l2_ioctls)
> >>  
> >> diff --git a/include/media/v4l2-ioctl.h b/include/media/v4l2-ioctl.h
> >> index edb733f21604..bdbb7e542321 100644
> >> --- a/include/media/v4l2-ioctl.h
> >> +++ b/include/media/v4l2-ioctl.h
> >> @@ -163,6 +163,8 @@ struct v4l2_fh;
> >>   *	:ref:`VIDIOC_CREATE_BUFS <vidioc_create_bufs>` ioctl
> >>   * @vidioc_prepare_buf: pointer to the function that implements
> >>   *	:ref:`VIDIOC_PREPARE_BUF <vidioc_prepare_buf>` ioctl
> >> + * @vidioc_remove_bufs: pointer to the function that implements
> >> + *	:ref:`VIDIOC_REMOVE_BUFS <vidioc_remove_bufs>` ioctl
> >>   * @vidioc_overlay: pointer to the function that implements
> >>   *	:ref:`VIDIOC_OVERLAY <vidioc_overlay>` ioctl
> >>   * @vidioc_g_fbuf: pointer to the function that implements
> >> @@ -422,6 +424,8 @@ struct v4l2_ioctl_ops {
> >>  				  struct v4l2_create_buffers *b);
> >>  	int (*vidioc_prepare_buf)(struct file *file, void *fh,
> >>  				  struct v4l2_buffer *b);
> >> +	int (*vidioc_remove_bufs)(struct file *file, void *fh,
> >> +				  struct v4l2_remove_buffers *d);
> >>  
> >>  	int (*vidioc_overlay)(struct file *file, void *fh, unsigned int i);
> >>  	int (*vidioc_g_fbuf)(struct file *file, void *fh,
> >> diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
> >> index b9333e2c7797..955237ac503d 100644
> >> --- a/include/media/videobuf2-core.h
> >> +++ b/include/media/videobuf2-core.h
> >> @@ -870,6 +870,16 @@ int vb2_core_create_bufs(struct vb2_queue *q, enum vb2_memory memory,
> >>   */
> >>  int vb2_core_prepare_buf(struct vb2_queue *q, struct vb2_buffer *vb, void *pb);
> >>  
> >> +/**
> >> + * vb2_core_remove_bufs() -
> >> + * @q:		pointer to &struct vb2_queue with videobuf2 queue.
> >> + * @start:	first index of the range of buffers to remove.
> >> + * @count:	number of buffers to remove.
> >> + *
> >> + *  Return: returns zero on success; an error code otherwise.
> >> + */
> >> +int vb2_core_remove_bufs(struct vb2_queue *q, unsigned int start, unsigned int count);
> >> +
> >>  /**
> >>   * vb2_core_qbuf() - Queue a buffer from userspace
> >>   *
> >> diff --git a/include/media/videobuf2-v4l2.h b/include/media/videobuf2-v4l2.h
> >> index 5a845887850b..77ce8238ab30 100644
> >> --- a/include/media/videobuf2-v4l2.h
> >> +++ b/include/media/videobuf2-v4l2.h
> >> @@ -334,6 +334,8 @@ int vb2_ioctl_streamon(struct file *file, void *priv, enum v4l2_buf_type i);
> >>  int vb2_ioctl_streamoff(struct file *file, void *priv, enum v4l2_buf_type i);
> >>  int vb2_ioctl_expbuf(struct file *file, void *priv,
> >>  	struct v4l2_exportbuffer *p);
> >> +int vb2_ioctl_remove_bufs(struct file *file, void *priv,
> >> +			  struct v4l2_remove_buffers *p);
> >>  
> >>  /* struct v4l2_file_operations helpers */
> >>  
> >> diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
> >> index a8015e5e7fa4..2663213b76a4 100644
> >> --- a/include/uapi/linux/videodev2.h
> >> +++ b/include/uapi/linux/videodev2.h
> >> @@ -1036,6 +1036,7 @@ struct v4l2_requestbuffers {
> >>  #define V4L2_BUF_CAP_SUPPORTS_M2M_HOLD_CAPTURE_BUF	(1 << 5)
> >>  #define V4L2_BUF_CAP_SUPPORTS_MMAP_CACHE_HINTS		(1 << 6)
> >>  #define V4L2_BUF_CAP_SUPPORTS_MAX_NUM_BUFFERS		(1 << 7)
> >> +#define V4L2_BUF_CAP_SUPPORTS_REMOVE_BUFS		(1 << 8)
> >>  
> >>  /**
> >>   * struct v4l2_plane - plane info for multi-planar buffers
> >> @@ -2624,6 +2625,20 @@ struct v4l2_create_buffers {
> >>  	__u32			reserved[5];
> >>  };
> >>  
> >> +/**
> >> + * struct v4l2_remove_buffers - VIDIOC_REMOVE_BUFS argument
> >> + * @index:	the first buffer to be removed
> >> + * @count:	number of buffers to removed
> >> + * @type:	enum v4l2_buf_type
> >> + * @reserved:	future extensions
> >> + */
> >> +struct v4l2_remove_buffers {
> >> +	__u32			index;
> >> +	__u32			count;
> >> +	__u32			type;
> >> +	__u32			reserved[13];
> >> +};
> >> +
> >>  /*
> >>   *	I O C T L   C O D E S   F O R   V I D E O   D E V I C E S
> >>   *
> >> @@ -2723,6 +2738,8 @@ struct v4l2_create_buffers {
> >>  #define VIDIOC_DBG_G_CHIP_INFO  _IOWR('V', 102, struct v4l2_dbg_chip_info)
> >>  
> >>  #define VIDIOC_QUERY_EXT_CTRL	_IOWR('V', 103, struct v4l2_query_ext_ctrl)
> >> +#define VIDIOC_REMOVE_BUFS	_IOWR('V', 104, struct v4l2_remove_buffers)
> >> +
> >>  
> >>  /* Reminder: when adding new ioctls please add support for them to
> >>     drivers/media/v4l2-core/v4l2-compat-ioctl32.c as well! */  
> > 
> > 
> > 
> > Thanks,
> > Mauro  
> 



Thanks,
Mauro