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Message-ID: <2bcbe941-ffc8-4b95-a5d1-0bcb9c2ddcb6@xs4all.nl>
Date: Thu, 21 Mar 2024 15:24:43 +0100
Precedence: bulk
MIME-Version: 1.0
User-Agent: Mozilla Thunderbird
Subject: Re: [PATCH v21 7/9] media: v4l2: Add REMOVE_BUFS ioctl
Content-Language: en-US, nl
To: Mauro Carvalho Chehab <mchehab@kernel.org>,
 Benjamin Gaignard <benjamin.gaignard@collabora.com>
Cc: tfiga@chromium.org, m.szyprowski@samsung.com,
 ezequiel@vanguardiasur.com.ar, p.zabel@pengutronix.de, nicolas@ndufresne.ca,
 linux-media@vger.kernel.org, linux-kernel@vger.kernel.org,
 linux-rockchip@lists.infradead.org, kernel@collabora.com
References: <20240314153226.197445-1-benjamin.gaignard@collabora.com>
 <20240314153226.197445-8-benjamin.gaignard@collabora.com>
 <20240321151442.0487b53f@coco.lan>
From: Hans Verkuil <hverkuil-cisco@xs4all.nl>
In-Reply-To: <20240321151442.0487b53f@coco.lan>
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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).

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