On 24/01/2024 13:33, Hans Verkuil wrote:
> On 19/01/2024 10:49, Benjamin Gaignard wrote:
>> VIDIOC_DELETE_BUFS ioctl allows to delete buffers from a queue.
>> The number of buffers to delete in given by count field of
>> struct v4l2_delete_buffers and the range start at the index
>> specified in the same structure.
>>
>> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@xxxxxxxxxxxxx>
>> ---
>> version 17:
>> - rework DELETE_BUFS documentation
>>
>> .../userspace-api/media/v4l/user-func.rst | 1 +
>> .../media/v4l/vidioc-delete-bufs.rst | 80 +++++++++++++++++++
>> .../media/v4l/vidioc-reqbufs.rst | 1 +
>> .../media/common/videobuf2/videobuf2-core.c | 42 ++++++++++
>> .../media/common/videobuf2/videobuf2-v4l2.c | 20 +++++
>> drivers/media/v4l2-core/v4l2-dev.c | 1 +
>> drivers/media/v4l2-core/v4l2-ioctl.c | 20 +++++
>> include/media/v4l2-ioctl.h | 4 +
>> include/media/videobuf2-core.h | 12 +++
>> include/media/videobuf2-v4l2.h | 13 +++
>> include/uapi/linux/videodev2.h | 17 ++++
>> 11 files changed, 211 insertions(+)
>> create mode 100644 Documentation/userspace-api/media/v4l/vidioc-delete-bufs.rst
>>
>> diff --git a/Documentation/userspace-api/media/v4l/user-func.rst b/Documentation/userspace-api/media/v4l/user-func.rst
>> index 15ff0bf7bbe6..3fd567695477 100644
>> --- a/Documentation/userspace-api/media/v4l/user-func.rst
>> +++ b/Documentation/userspace-api/media/v4l/user-func.rst
>> @@ -17,6 +17,7 @@ Function Reference
>> vidioc-dbg-g-chip-info
>> vidioc-dbg-g-register
>> vidioc-decoder-cmd
>> + vidioc-delete-bufs
>> vidioc-dqevent
>> vidioc-dv-timings-cap
>> vidioc-encoder-cmd
>> diff --git a/Documentation/userspace-api/media/v4l/vidioc-delete-bufs.rst b/Documentation/userspace-api/media/v4l/vidioc-delete-bufs.rst
>> new file mode 100644
>> index 000000000000..d409063ceb3f
>> --- /dev/null
>> +++ b/Documentation/userspace-api/media/v4l/vidioc-delete-bufs.rst
>> @@ -0,0 +1,80 @@
>> +.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
>> +.. c:namespace:: V4L
>> +
>> +.. _VIDIOC_DELETE_BUFS:
>> +
>> +************************
>> +ioctl VIDIOC_DELETE_BUFS
>> +************************
>> +
>> +Name
>> +====
>> +
>> +VIDIOC_DELETE_BUFS - Deletes buffers from a queue
>> +
>> +Synopsis
>> +========
>> +
>> +.. c:macro:: VIDIOC_DELETE_BUFs
>> +
>> +``int ioctl(int fd, VIDIOC_DELETE_BUFs, struct v4l2_delete_buffers *argp)``
>> +
>> +Arguments
>> +=========
>> +
>> +``fd``
>> + File descriptor returned by :c:func:`open()`.
>> +
>> +``argp``
>> + Pointer to struct :c:type:`v4l2_delete_buffers`.
>> +
>> +Description
>> +===========
>> +
>> +Applications can optionally call the :ref:`VIDIOC_DELETE_BUFS` ioctl to
>> +delete buffers from a queue.
>> +This ioctl is available if the ``V4L2_BUF_CAP_SUPPORTS_DELETE_BUFS`` capability
>> +is set on the queue when :c:func:`VIDIOC_REQBUFS` or :c:func:`VIDIOC_CREATE_BUFS`
>> +are invoked.
>> +
>> +.. c:type:: v4l2_delete_buffers
>> +
>> +.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.5cm}|
>> +
>> +.. flat-table:: struct v4l2_delete_buffers
>> + :header-rows: 0
>> + :stub-columns: 0
>> + :widths: 1 1 2
>> +
>> + * - __u32
>> + - ``index``
>> + - The starting buffer index to delete.
>> + * - __u32
>> + - ``count``
>> + - The number of buffers to be deleted with indices 'index' until 'index + count - 1'.
>> + All buffers in this range must be valid and in DEQUEUED state.
>> + If count is set to 0 :ref:`VIDIOC_DELETE_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.
>> +
>> +EBUSY
>> + File I/O is in progress.
>> + Any buffer in range ``index`` to ``index + count - 1`` is not in
>> + DEQUEUED state.
>> +
>> +EINVAL
>> + Any buffer in range ``index`` to ``index + count - 1`` doesn't exist in the queue.
>> diff --git a/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst b/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst
>> index 0b3a41a45d05..14d4a49c2945 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-DELETE-BUFS:
>>
>> .. raw:: latex
>>
>> diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c
>> index 010505ed92e8..99e631233a54 100644
>> --- a/drivers/media/common/videobuf2/videobuf2-core.c
>> +++ b/drivers/media/common/videobuf2/videobuf2-core.c
>> @@ -1688,6 +1688,48 @@ 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_delete_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;
>> +
>> + if (start + count > q->max_num_buffers)
>
> Change this to:
>
> if (start > q->max_num_buffers - count)
>
> This avoids the corner case where 'start + count' overflows the unsigned int.
>
>> + return -EINVAL;
>> +
>> + /* If streaming keep at least min_queued_buffers + 1 buffers */
>> + if (q->streaming && (q_num_bufs - count < q->min_queued_buffers + 1))
>> + return -EINVAL;
>
> I would drop this. This will be caught automatically by the next check
> since if a driver needs q->min_queued_buffers to start the DMA, then
> once the DMA stated there will always be that amount of buffers in a
> non-DEQUEUED state.
>
>> +
>> + 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 deleted\n", count);
>> +
>> +unlock:
>> + mutex_unlock(&q->mmap_lock);
>> + return ret;
>> +}
>> +EXPORT_SYMBOL_GPL(vb2_core_delete_bufs);
>
> There is one specific corner case here that needs attention: if ALL buffers
> are deleted (something that is possible if STREAMON was called, but no
> buffers are queued), then vb2_is_busy will suddenly return false.
>
> This can have all sorts of subtle consequences since it is now possible
> to, for example, change the format.
>
> There are two options here:
>
> 1) vb2_is_busy() shouldn't check if there are buffers allocated, instead it
> should check if buffers were allocated at least once. So calling REQBUFS
> or CREATE_BUFS for the first time will set a flag to 1, until you call
> REQBUFS with count 0, or close the filehandle. Deleting all buffers with
> DELETE_BUFS will not change that.
>
> 2) We treat deleting all buffers with DELETE_BUFS the same as calling REQBUFS(0),
> in which case the code above needs to change.
>
> I lean towards option 1. My reasoning is that REQBUFS does an implicit STREAMOFF,
> and DELETE_BUFS does not and I do not think DELETE_BUFS should allow vb2_is_busy()
> to become false. It would still be nice if it can delete all buffers, but we
> would have to check if there are no other places where the number of allocated
> buffers is checked, when perhaps it really should use vb2_is_busy() instead.
If we go for 1, then it is probably best to add a new patch early in the patch
series that changes vb2_is_busy() from 'buffers are allocated' to 'at least one
buffer has been allocated at some time'.
Regards,
Hans
>
>> +
>> /*
>> * 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..626b5283dfdb 100644
>> --- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
>> +++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
>> @@ -698,6 +698,8 @@ static void vb2_set_flags_and_caps(struct vb2_queue *q, u32 memory,
>> *caps |= V4L2_BUF_CAP_SUPPORTS_MMAP_CACHE_HINTS;
>> if (q->supports_requests)
>> *caps |= V4L2_BUF_CAP_SUPPORTS_REQUESTS;
>> + if (q->supports_delete_bufs)
>> + *caps |= V4L2_BUF_CAP_SUPPORTS_DELETE_BUFS;
>> if (max_num_bufs) {
>> *max_num_bufs = q->max_num_buffers;
>> *caps |= V4L2_BUF_CAP_SUPPORTS_MAX_NUM_BUFFERS;
>> @@ -743,6 +745,12 @@ int vb2_prepare_buf(struct vb2_queue *q, struct media_device *mdev,
>> }
>> EXPORT_SYMBOL_GPL(vb2_prepare_buf);
>>
>> +int vb2_delete_bufs(struct vb2_queue *q, struct v4l2_delete_buffers *d)
>> +{
>> + return vb2_core_delete_bufs(q, d->index, d->count);
>> +}
>> +EXPORT_SYMBOL_GPL(vb2_delete_bufs);
>> +
>
> I would not add this. Drivers that want to support this should implement
> vb2_ioctl_delete_bufs(). Eventually I want to get away from these non-vb2_ioctl_
> functions.
>
>> int vb2_create_bufs(struct vb2_queue *q, struct v4l2_create_buffers *create)
>> {
>> unsigned requested_planes = 1;
>> @@ -1001,6 +1009,18 @@ EXPORT_SYMBOL_GPL(vb2_poll);
>>
>> /* vb2 ioctl helpers */
>>
>> +int vb2_ioctl_delete_bufs(struct file *file, void *priv,
>> + struct v4l2_delete_buffers *p)
>> +{
>> + struct video_device *vdev = video_devdata(file);
>> +
>> + if (vb2_queue_is_busy(vdev->queue, file))
>> + return -EBUSY;
>> +
>> + return vb2_delete_bufs(vdev->queue, p);
>> +}
>> +EXPORT_SYMBOL_GPL(vb2_ioctl_delete_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..e764af2e29ff 100644
>> --- a/drivers/media/v4l2-core/v4l2-dev.c
>> +++ b/drivers/media/v4l2-core/v4l2-dev.c
>> @@ -722,6 +722,7 @@ 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);
>> + SET_VALID_IOCTL(ops, VIDIOC_DELETE_BUFS, vidioc_delete_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 33076af4dfdb..9676cd758426 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_delete_buffers(const void *arg, bool write_only)
>> +{
>> + const struct v4l2_delete_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;
>> @@ -2161,6 +2169,17 @@ static int v4l_prepare_buf(const struct v4l2_ioctl_ops *ops,
>> return ret ? ret : ops->vidioc_prepare_buf(file, fh, b);
>> }
>>
>> +static int v4l_delete_bufs(const struct v4l2_ioctl_ops *ops,
>> + struct file *file, void *fh, void *arg)
>> +{
>> + struct v4l2_delete_buffers *delete = arg;
>> + int ret = check_fmt(file, delete->type);
>> +
>> + memset_after(delete, 0, type);
>
> I don't think this is needed since you use INFO_FL_CLEAR() below. That does it for you.
>
>> +
>> + return ret ? ret : ops->vidioc_delete_bufs(file, fh, delete);
>> +}
>> +
>> static int v4l_g_parm(const struct v4l2_ioctl_ops *ops,
>> struct file *file, void *fh, void *arg)
>> {
>> @@ -2910,6 +2929,7 @@ 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_DELETE_BUFS, v4l_delete_bufs, v4l_print_delete_buffers, INFO_FL_PRIO | INFO_FL_QUEUE | INFO_FL_CLEAR(v4l2_delete_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..55afbde54211 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_delete_bufs: pointer to the function that implements
>> + * :ref:`VIDIOC_DELETE_BUFS <vidioc_delete_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_delete_bufs)(struct file *file, void *fh,
>> + struct v4l2_delete_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 8647eee348bd..4e62b31561d9 100644
>> --- a/include/media/videobuf2-core.h
>> +++ b/include/media/videobuf2-core.h
>> @@ -507,6 +507,7 @@ struct vb2_buf_ops {
>> * @supports_requests: this queue supports the Request API.
>> * @requires_requests: this queue requires the Request API. If this is set to 1,
>> * then supports_requests must be set to 1 as well.
>> + * @supports_delete_bufs: this queue supports DELETE_BUFS ioctl.
>> * @uses_qbuf: qbuf was used directly for this queue. Set to 1 the first
>> * time this is called. Set to 0 when the queue is canceled.
>> * If this is 1, then you cannot queue buffers from a request.
>> @@ -613,6 +614,7 @@ struct vb2_queue {
>> unsigned int quirk_poll_must_check_waiting_for_buffers:1;
>> unsigned int supports_requests:1;
>> unsigned int requires_requests:1;
>> + unsigned int supports_delete_bufs:1;
>
> I am not convinced we want do enable this per-queue. i will have
> to think some more about this.
>
>> unsigned int uses_qbuf:1;
>> unsigned int uses_requests:1;
>> unsigned int allow_cache_hints:1;
>> @@ -865,6 +867,16 @@ 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_delete_bufs() -
>> + * @q: pointer to &struct vb2_queue with videobuf2 queue.
>> + * @start: first index of the range of buffers to delete.
>> + * @count: number of buffers to delete.
>> + *
>> + * Return: returns zero on success; an error code otherwise.
>> + */
>> +int vb2_core_delete_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..79cea8459f52 100644
>> --- a/include/media/videobuf2-v4l2.h
>> +++ b/include/media/videobuf2-v4l2.h
>> @@ -118,6 +118,17 @@ int vb2_create_bufs(struct vb2_queue *q, struct v4l2_create_buffers *create);
>> */
>> int vb2_prepare_buf(struct vb2_queue *q, struct media_device *mdev,
>> struct v4l2_buffer *b);
>> +/**
>> + * vb2_delete_bufs() - Delete buffers from the queue
>> + *
>> + * @q: pointer to &struct vb2_queue with videobuf2 queue.
>> + * @d: delete parameter, passed from userspace to
>> + * &v4l2_ioctl_ops->vidioc_delete_bufs handler in driver
>> + *
>> + * The return values from this function are intended to be directly returned
>> + * from &v4l2_ioctl_ops->vidioc_delete_bufs handler in driver.
>> + */
>> +int vb2_delete_bufs(struct vb2_queue *q, struct v4l2_delete_buffers *d);
>
> Drop this.
>
>>
>> /**
>> * vb2_qbuf() - Queue a buffer from userspace
>> @@ -334,6 +345,8 @@ 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_delete_bufs(struct file *file, void *priv,
>> + struct v4l2_delete_buffers *p);
>>
>> /* struct v4l2_file_operations helpers */
>>
>> diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
>> index 68e7ac178cc2..ce436f924782 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_DELETE_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_delete_buffers - VIDIOC_DELETE_BUFS argument
>> + * @index: the first buffer to be deleted
>> + * @count: number of buffers to delete
>> + * @type: enum v4l2_buf_type
>> + * @reserved: future extensions
>> + */
>> +struct v4l2_delete_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_DELETE_BUFS _IOWR('V', 104, struct v4l2_delete_buffers)
>> +
>>
>> /* Reminder: when adding new ioctls please add support for them to
>> drivers/media/v4l2-core/v4l2-compat-ioctl32.c as well! */
>
> Regards,
>
> Hans
>
