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    Subject[PATCH v14 44/56] media: core: Report the maximum possible number of buffers for the queue
    Date
    Use one of the struct v4l2_create_buffers reserved bytes to report
    the maximum possible number of buffers for the queue.
    V4l2 framework set V4L2_BUF_CAP_SUPPORTS_MAX_NUM_BUFFERS flags in queue
    capabilities so userland can know when the field is valid.
    Does the same change in v4l2_create_buffers32 structure.

    Signed-off-by: Benjamin Gaignard <benjamin.gaignard@collabora.com>
    ---
    .../userspace-api/media/v4l/vidioc-create-bufs.rst | 8 ++++++--
    Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst | 1 +
    drivers/media/common/videobuf2/videobuf2-v4l2.c | 2 ++
    drivers/media/v4l2-core/v4l2-compat-ioctl32.c | 9 ++++++++-
    drivers/media/v4l2-core/v4l2-ioctl.c | 4 ++--
    include/uapi/linux/videodev2.h | 7 ++++++-
    6 files changed, 25 insertions(+), 6 deletions(-)

    diff --git a/Documentation/userspace-api/media/v4l/vidioc-create-bufs.rst b/Documentation/userspace-api/media/v4l/vidioc-create-bufs.rst
    index a048a9f6b7b6..49232c9006c2 100644
    --- a/Documentation/userspace-api/media/v4l/vidioc-create-bufs.rst
    +++ b/Documentation/userspace-api/media/v4l/vidioc-create-bufs.rst
    @@ -116,9 +116,13 @@ than the number requested.
    - ``flags``
    - Specifies additional buffer management attributes.
    See :ref:`memory-flags`.
    -
    * - __u32
    - - ``reserved``\ [6]
    + - ``max_num_buffers``
    + - If the V4L2_BUF_CAP_SUPPORTS_MAX_NUM_BUFFERS capability flag is set
    + this field indicates the maximum possible number of buffers
    + for this queue.
    + * - __u32
    + - ``reserved``\ [5]
    - A place holder for future extensions. Drivers and applications
    must set the array to zero.

    diff --git a/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst b/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst
    index 099fa6695167..0b3a41a45d05 100644
    --- a/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst
    +++ b/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst
    @@ -120,6 +120,7 @@ aborting or finishing any DMA in progress, an implicit
    .. _V4L2-BUF-CAP-SUPPORTS-ORPHANED-BUFS:
    .. _V4L2-BUF-CAP-SUPPORTS-M2M-HOLD-CAPTURE-BUF:
    .. _V4L2-BUF-CAP-SUPPORTS-MMAP-CACHE-HINTS:
    +.. _V4L2-BUF-CAP-SUPPORTS-MAX-NUM-BUFFERS:

    .. raw:: latex

    diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c b/drivers/media/common/videobuf2/videobuf2-v4l2.c
    index f3cf4b235c1f..bdfc3a253c65 100644
    --- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
    +++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
    @@ -762,6 +762,8 @@ int vb2_create_bufs(struct vb2_queue *q, struct v4l2_create_buffers *create)
    fill_buf_caps(q, &create->capabilities);
    validate_memory_flags(q, create->memory, &create->flags);
    create->index = vb2_get_num_buffers(q);
    + create->max_num_buffers = q->max_num_buffers;
    + create->capabilities |= V4L2_BUF_CAP_SUPPORTS_MAX_NUM_BUFFERS;
    if (create->count == 0)
    return ret != -EBUSY ? ret : 0;

    diff --git a/drivers/media/v4l2-core/v4l2-compat-ioctl32.c b/drivers/media/v4l2-core/v4l2-compat-ioctl32.c
    index f3bed37859a2..5aac5cf780b3 100644
    --- a/drivers/media/v4l2-core/v4l2-compat-ioctl32.c
    +++ b/drivers/media/v4l2-core/v4l2-compat-ioctl32.c
    @@ -116,6 +116,9 @@ struct v4l2_format32 {
    * @flags: additional buffer management attributes (ignored unless the
    * queue has V4L2_BUF_CAP_SUPPORTS_MMAP_CACHE_HINTS capability and
    * configured for MMAP streaming I/O).
    + * @max_num_buffers: if V4L2_BUF_CAP_SUPPORTS_MAX_NUM_BUFFERS capability flag is set
    + * this field indicate the maximum possible number of buffers
    + * for this queue.
    * @reserved: future extensions
    */
    struct v4l2_create_buffers32 {
    @@ -125,7 +128,8 @@ struct v4l2_create_buffers32 {
    struct v4l2_format32 format;
    __u32 capabilities;
    __u32 flags;
    - __u32 reserved[6];
    + __u32 max_num_buffers;
    + __u32 reserved[5];
    };

    static int get_v4l2_format32(struct v4l2_format *p64,
    @@ -175,6 +179,8 @@ static int get_v4l2_create32(struct v4l2_create_buffers *p64,
    return -EFAULT;
    if (copy_from_user(&p64->flags, &p32->flags, sizeof(p32->flags)))
    return -EFAULT;
    + if (copy_from_user(&p64->max_num_buffers, &p32->max_num_buffers, sizeof(p32->max_num_buffers)))
    + return -EFAULT;
    return get_v4l2_format32(&p64->format, &p32->format);
    }

    @@ -221,6 +227,7 @@ static int put_v4l2_create32(struct v4l2_create_buffers *p64,
    offsetof(struct v4l2_create_buffers32, format)) ||
    put_user(p64->capabilities, &p32->capabilities) ||
    put_user(p64->flags, &p32->flags) ||
    + put_user(p64->max_num_buffers, &p32->max_num_buffers) ||
    copy_to_user(p32->reserved, p64->reserved, sizeof(p64->reserved)))
    return -EFAULT;
    return put_v4l2_format32(&p64->format, &p32->format);
    diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c
    index 9b1de54ce379..4d90424cbfc4 100644
    --- a/drivers/media/v4l2-core/v4l2-ioctl.c
    +++ b/drivers/media/v4l2-core/v4l2-ioctl.c
    @@ -483,9 +483,9 @@ static void v4l_print_create_buffers(const void *arg, bool write_only)
    {
    const struct v4l2_create_buffers *p = arg;

    - pr_cont("index=%d, count=%d, memory=%s, capabilities=0x%08x, ",
    + pr_cont("index=%d, count=%d, memory=%s, capabilities=0x%08x, max num buffers=%u",
    p->index, p->count, prt_names(p->memory, v4l2_memory_names),
    - p->capabilities);
    + p->capabilities, p->max_num_buffers);
    v4l_print_format(&p->format, write_only);
    }

    diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
    index c3d4e490ce7c..13ddb5abf584 100644
    --- a/include/uapi/linux/videodev2.h
    +++ b/include/uapi/linux/videodev2.h
    @@ -1035,6 +1035,7 @@ struct v4l2_requestbuffers {
    #define V4L2_BUF_CAP_SUPPORTS_ORPHANED_BUFS (1 << 4)
    #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)

    /**
    * struct v4l2_plane - plane info for multi-planar buffers
    @@ -2605,6 +2606,9 @@ struct v4l2_dbg_chip_info {
    * @flags: additional buffer management attributes (ignored unless the
    * queue has V4L2_BUF_CAP_SUPPORTS_MMAP_CACHE_HINTS capability
    * and configured for MMAP streaming I/O).
    + * @max_num_buffers: if V4L2_BUF_CAP_SUPPORTS_MAX_NUM_BUFFERS capability flag is set
    + * this field indicate the maximum possible number of buffers
    + * for this queue.
    * @reserved: future extensions
    */
    struct v4l2_create_buffers {
    @@ -2614,7 +2618,8 @@ struct v4l2_create_buffers {
    struct v4l2_format format;
    __u32 capabilities;
    __u32 flags;
    - __u32 reserved[6];
    + __u32 max_num_buffers;
    + __u32 reserved[5];
    };

    /*
    --
    2.39.2
    \
     
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      Last update: 2023-10-31 17:37    [W:4.253 / U:0.720 seconds]
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