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

From: Hans Verkuil
Date: Fri Mar 22 2024 - 03:55:08 EST

Hi Benjamin,

I added the one additional sentence to vidioc-remove-bufs.rst as suggested
by Mauro, and added his Reviewed/Acked-by lines.

I'll merge this series on Monday after 6.9-rc1 has been released and then
I will also merge the v4l-utils patches.

No need for you to do anything.

Thank you for all your work on this!

Hans

On 21/03/2024 4:03 pm, Mauro Carvalho Chehab wrote:
> Em Thu, 21 Mar 2024 15:24:43 +0100
> Hans Verkuil <hverkuil-cisco@xxxxxxxxx> 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@xxxxxxxxxxxxx> 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@xxxxxxxxxxxxx>
>>>> ---
>>>> 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@xxxxxxxxxx>
>
>>
>> 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
>