Re: [PATCH v3 10/11] media: v4l2: Add DELETE_BUF ioctl

[Benjamin Gaignard <benjamin.gaignard@xxxxxxxxxxxxx>]

Le 27/06/2023 à 09:30, Hsia-Jun Li a écrit :
> On 6/22/23 21:13, Benjamin Gaignard wrote:
> > CAUTION: Email originated externally, do not click links or open 
> > attachments unless you recognize the sender and know the content is 
> > safe.
> >
> >
> > VIDIOC_DELETE_BUF ioctl allows to delete a buffer from a queue.
> >
> > Signed-off-by: Benjamin Gaignard <benjamin.gaignard@xxxxxxxxxxxxx>
> > ---
> >   .../userspace-api/media/v4l/user-func.rst     |  1 +
> >   .../media/v4l/vidioc-delete-buf.rst           | 51 +++++++++++++++++++
> >   .../media/common/videobuf2/videobuf2-core.c   | 33 ++++++++++++
> >   .../media/common/videobuf2/videobuf2-v4l2.c   |  6 +++
> >   drivers/media/v4l2-core/v4l2-dev.c            |  1 +
> >   drivers/media/v4l2-core/v4l2-ioctl.c          | 10 ++++
> >   include/media/v4l2-ioctl.h                    |  4 ++
> >   include/media/videobuf2-core.h                |  9 ++++
> >   include/media/videobuf2-v4l2.h                | 11 ++++
> >   include/uapi/linux/videodev2.h                |  2 +
> >   10 files changed, 128 insertions(+)
> >   create mode 100644 
> > Documentation/userspace-api/media/v4l/vidioc-delete-buf.rst
> >
> > diff --git a/Documentation/userspace-api/media/v4l/user-func.rst 
> > b/Documentation/userspace-api/media/v4l/user-func.rst
> > index 15ff0bf7bbe6..8c74016e12fd 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-buf
> >       vidioc-dqevent
> >       vidioc-dv-timings-cap
> >       vidioc-encoder-cmd
> > diff --git 
> > a/Documentation/userspace-api/media/v4l/vidioc-delete-buf.rst 
> > b/Documentation/userspace-api/media/v4l/vidioc-delete-buf.rst
> > new file mode 100644
> > index 000000000000..0e7ce58f91bc
> > --- /dev/null
> > +++ b/Documentation/userspace-api/media/v4l/vidioc-delete-buf.rst
> > @@ -0,0 +1,51 @@
> > +.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
> > +.. c:namespace:: V4L
> > +
> > +.. _VIDIOC_DELETE_BUF:
> > +
> > +************************
> > +ioctl VIDIOC_DELETE_BUF
> > +************************
> > +
> > +Name
> > +====
> > +
> > +VIDIOC_DELETE_BUF - Delete a buffer from a queue
> > +
> > +Synopsis
> > +========
> > +
> > +.. c:macro:: VIDIOC_DELETE_BUF
> > +
> > +``int ioctl(int fd, VIDIOC_DELETE_BUF, struct v4l2_buffer *argp)``
> > +
> > +Arguments
> > +=========
> > +
> > +``fd``
> > +    File descriptor returned by :c:func:`open()`.
> > +
> > +``argp``
> > +    Pointer to struct :c:type:`v4l2_buffer`.
> > +
> > +Description
> > +===========
> > +
> > +Applications can optionally call the :ref:`VIDIOC_DELETE_BUF` ioctl to
> > +delete a buffer from a queue.
> > +
> > +The struct :c:type:`v4l2_buffer` structure is specified in
> > +:ref:`buffer`.
> > +
> > +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.
> > +
> > +EINVAL
> > +    The buffer ``index`` doesn't exist in the queue.
> > diff --git a/drivers/media/common/videobuf2/videobuf2-core.c 
> > b/drivers/media/common/videobuf2/videobuf2-core.c
> > index 899783f67580..aa546c972c3d 100644
> > --- a/drivers/media/common/videobuf2/videobuf2-core.c
> > +++ b/drivers/media/common/videobuf2/videobuf2-core.c
> > @@ -1637,6 +1637,39 @@ int vb2_core_prepare_buf(struct vb2_queue *q, 
> > unsigned int index, void *pb)
> >   }
> >   EXPORT_SYMBOL_GPL(vb2_core_prepare_buf);
> >
> > +int vb2_core_delete_buf(struct vb2_queue *q, unsigned int index)
> > +{
> > +       struct vb2_buffer *vb;
> > +
> > +       vb = vb2_get_buffer(q, index);
> > +       if (!vb) {
> > +               dprintk(q, 1, "invalid buffer index %d\n", index);
> > +               return -EINVAL;
> > +       }
> > +
> > +       if (vb->state != VB2_BUF_STATE_DEQUEUED) {
> > +               dprintk(q, 1, "can't delete non dequeued buffer index 
> > %d\n", index);
> > +               return -EINVAL;
> > +       }
> > +
> I know the driver could implement its own 
> v4l2_ioctl_ops->vidioc_delete_buf() that check whether a buffer is 
> used by the hardware as a future reference frame.
> But I think we need a flag to let the user know which buffer is still 
> used by the hardware.
> Alternative ref case is safe, we only know it's existing when it is 
> dequeued in current V4L2 buffer mechanism.
> While the Golden reference frame, such long term reference frame could 
> last much longer.

It is up to userland stack to know frames life time, it got the information for that.

> > +       if (vb->planes[0].mem_priv)
> > +               call_void_vb_qop(vb, buf_cleanup, vb);
> > +
> > +       /* Free MMAP buffers or release USERPTR buffers */
> > +       if (q->memory == VB2_MEMORY_MMAP)
> > +               __vb2_buf_mem_free(vb);
> > +       else if (q->memory == VB2_MEMORY_DMABUF)
> > +               __vb2_buf_dmabuf_put(vb);
> > +       else
> > +               __vb2_buf_userptr_put(vb);
> > +
> > +       vb2_queue_remove_buffer(q, vb);
> > +       kfree(vb);
> > +
> > +       dprintk(q, 2, "buffer %d deleted\n", index);
> > +       return 0;
> > +}
> > +
> >   /*
> >    * 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 724135d41f7f..cea666c17b41 100644
> > --- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
> > +++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
> > @@ -751,6 +751,12 @@ int vb2_prepare_buf(struct vb2_queue *q, struct 
> > media_device *mdev,
> >   }
> >   EXPORT_SYMBOL_GPL(vb2_prepare_buf);
> >
> > +int vb2_delete_buf(struct vb2_queue *q, struct v4l2_buffer *b)
> > +{
> > +       return vb2_core_delete_buf(q, b->index);
> > +}
> > +EXPORT_SYMBOL_GPL(vb2_delete_buf);
> > +
> >   int vb2_create_bufs(struct vb2_queue *q, struct v4l2_create_buffers 
> > *create)
> >   {
> >          unsigned requested_planes = 1;
> > diff --git a/drivers/media/v4l2-core/v4l2-dev.c 
> > b/drivers/media/v4l2-core/v4l2-dev.c
> > index f81279492682..80ace2e1e932 100644
> > --- a/drivers/media/v4l2-core/v4l2-dev.c
> > +++ b/drivers/media/v4l2-core/v4l2-dev.c
> > @@ -720,6 +720,7 @@ 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_BUF, 
> > vidioc_delete_buf);
> >          }
> >
> >          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 a858acea6547..1c737279d3ef 100644
> > --- a/drivers/media/v4l2-core/v4l2-ioctl.c
> > +++ b/drivers/media/v4l2-core/v4l2-ioctl.c
> > @@ -2156,6 +2156,15 @@ 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_buf(const struct v4l2_ioctl_ops *ops,
> > +                         struct file *file, void *fh, void *arg)
> > +{
> > +       struct v4l2_buffer *b = arg;
> > +       int ret = check_fmt(file, b->type);
> > +
> > +       return ret ? ret : ops->vidioc_delete_buf(file, fh, b);
> > +}
> > +
> >   static int v4l_g_parm(const struct v4l2_ioctl_ops *ops,
> >                                  struct file *file, void *fh, void *arg)
> >   {
> > @@ -2905,6 +2914,7 @@ 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_BUF, v4l_delete_buf, 
> > v4l_print_buffer, INFO_FL_QUEUE),
> >   };
> >   #define V4L2_IOCTLS ARRAY_SIZE(v4l2_ioctls)
> >
> > diff --git a/include/media/v4l2-ioctl.h b/include/media/v4l2-ioctl.h
> > index edb733f21604..2f232ed884c7 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_buf: pointer to the function that implements
> > + *     :ref:`VIDIOC_DELETE_BUF <vidioc_delete_buf>` 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_buf)(struct file *file, void *fh,
> > +                                struct v4l2_buffer *b);
> >
> >          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 080b783d608d..0f9e68f76b77 100644
> > --- a/include/media/videobuf2-core.h
> > +++ b/include/media/videobuf2-core.h
> > @@ -840,6 +840,15 @@ int vb2_core_create_bufs(struct vb2_queue *q, 
> > enum vb2_memory memory,
> >    */
> >   int vb2_core_prepare_buf(struct vb2_queue *q, unsigned int index, 
> > void *pb);
> >
> > +/**
> > + * vb2_core_delete_buf() -
> > + * @q: pointer to &struct vb2_queue with videobuf2 queue.
> > + * @index:     id number of the buffer.
> > + *
> > + *  Return: returns zero on success; an error code otherwise.
> > + */
> > +int vb2_core_delete_buf(struct vb2_queue *q, unsigned int index);
> > +
> >   /**
> >    * vb2_core_qbuf() - Queue a buffer from userspace
> >    *
> > diff --git a/include/media/videobuf2-v4l2.h 
> > b/include/media/videobuf2-v4l2.h
> > index 88a7a565170e..3beeb4c735f0 100644
> > --- a/include/media/videobuf2-v4l2.h
> > +++ b/include/media/videobuf2-v4l2.h
> > @@ -114,6 +114,17 @@ 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_buf() - Delete the buffer from the queue
> > + *
> > + * @q:         pointer to &struct vb2_queue with videobuf2 queue.
> > + * @b:         buffer structure passed from userspace to
> > + *             &v4l2_ioctl_ops->vidioc_delete_buf handler in driver
> > + *
> > + * The return values from this function are intended to be directly 
> > returned
> > + * from &v4l2_ioctl_ops->vidioc_delete_buf handler in driver.
> > + */
> > +int vb2_delete_buf(struct vb2_queue *q, struct v4l2_buffer *b);
> >
> >   /**
> >    * vb2_qbuf() - Queue a buffer from userspace
> > diff --git a/include/uapi/linux/videodev2.h 
> > b/include/uapi/linux/videodev2.h
> > index aee75eb9e686..31bba1915642 100644
> > --- a/include/uapi/linux/videodev2.h
> > +++ b/include/uapi/linux/videodev2.h
> > @@ -2702,6 +2702,8 @@ 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_BUF      _IOWR('V', 104, struct v4l2_buffer)
> > +
> >
> >   /* Reminder: when adding new ioctls please add support for them to
> >      drivers/media/v4l2-core/v4l2-compat-ioctl32.c as well! */
> > --
> > 2.39.2