Message-ID: <c102d84a-d4e2-14e6-d1e2-2be0f6f72abc@synaptics.com>
Date:   Mon, 3 Jul 2023 19:06:40 +0800
From:   Hsia-Jun Li <Randy.Li@...aptics.com>
To:     Benjamin Gaignard <benjamin.gaignard@...labora.com>
Cc:     linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        p.zabel@...gutronix.de, ming.qian@....com,
        hverkuil-cisco@...all.nl, gregkh@...uxfoundation.org,
        ezequiel@...guardiasur.com.ar,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linux-arm-msm@...r.kernel.org,
        linux-rockchip@...ts.infradead.org, nicolas.dufresne@...labora.com,
        linux-staging@...ts.linux.dev, kernel@...labora.com,
        mchehab@...nel.org, tfiga@...omium.org, m.szyprowski@...sung.com,
        ayaka <ayaka@...lik.info>
Subject: Re: [PATCH v3 10/11] media: v4l2: Add DELETE_BUF ioctl

Sorry for html version, again.

On 7/3/23 18:35, 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.
>
>
> Le 03/07/2023 à 11:20, Hsia-Jun Li a écrit :
>>
>> On 7/3/23 16:52, 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.
>>>
>>>
>>> Le 03/07/2023 à 10:19, Hsia-Jun Li a écrit :
>>>>
>>>> On 7/3/23 16:12, 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.
>>>>>
>>>>>
>>>>> Le 30/06/2023 à 11:43, Hsia-Jun Li a écrit :
>>>>>>
>>>>>> On 6/27/23 16:47, Hsia-Jun Li wrote:
>>>>>>> CAUTION: Email originated externally, do not click links or open
>>>>>>> attachments unless you recognize the sender and know the content is
>>>>>>> safe.
>>>>>>>
>>>>>>>
>>>>>>> On 6/27/23 16:43, 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.
>>>>>>>>
>>>>>>>>
>>>>>>>> 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@...labora.com>
>>>>>>>>>> ---
>>>>>>>>>>   .../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.
>>>>>>>
>>>>>>> That is true for the stateless codec driver.
>>>>>>>
>>>>>>> While application for stateful decoder could never do that. It also
>>>>>>> breaks what the document said:
>>>>>>>
>>>>>>> "The backing memory of |CAPTURE| buffers that are used as reference
>>>>>>> frames by the stream may be read by the hardware even after they 
>>>>>>> are
>>>>>>> dequeued. Consequently, the client should avoid writing into this
>>>>>>> memory
>>>>>>> while the |CAPTURE| queue is streaming. Failure to observe this may
>>>>>>> result in corruption of decoded frames."
>>>>>>>
>>>>>>>>
>>>>>>>>>> +       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);
>>>>>>
>>>>>> Here is another problem for the existing application, the mmap() 
>>>>>> from
>>>>>> the mmap offset or exportbuffer fd would not create a reference to
>>>>>> buffer in this step(while the exportbuffer would create one itself).
>>>>>>
>>>>>> When you delete a buffer, you may not release it from its virtual
>>>>>> memory space, leaving a corrupted virtual memory space. Also this
>>>>>> behavior is right, because mmap(2) says:
>>>>>>
>>>>>> "After  the  mmap()  call has returned, the file descriptor, fd, can
>>>>>> be closed immediately without invalidating the map‐ping."
>>>>>
>>>>> Existing applications do not call DELETE_BUF ioctl and when call it
>>>>> they will be aware that the buffer is removed.
>>>>> I have done it in GStreamer:
>>>>> https://urldefense.proofpoint.com/v2/url?u=https-3A__gitlab.freedesktop.org_benjamin.gaignard1_gstreamer_-2D_commit_fca0fbc934f4440693ce0ff6c8dc8a2e5f5f17d9&d=DwIDaQ&c=7dfBJ8cXbWjhc0BhImu8wVIoUFmBzj1s88r8EGyM0UY&r=P4xb2_7biqBxD4LGGPrSV6j-jf3C3xlR7PXU-mLTeZE&m=TGH9toTzGRfO5aBsfaMvGbcOw-28q6cPmpX6vScbHjpCtaLtb-RuvBvsJ0z9RvAB&s=Ufl1ccfRZf2EhnfCBvnQzRJV9CDhGxl5spe9WNECspU&e= 
>>>>>
>>>>>
>>>>>
>>>>
>>>> I have read that.
>>>>
>>>> There is not a VP8 parser in Gstreamer, while a parser would not work
>>>> when deal with the secure video(userspace can't access the data
>>>> context at all).
>>>>
>>>> Besides, this adds extra work for the application for a stateful codec
>>>> driver. The application need to parser the bitstream and track the 
>>>> dpb.
>>>>
>>>> I don't mind if you could fix the nonfiction mechanism for those
>>>> non-display frame and internal reference state.
>>>>
>>>> That could be requirement for codec firmware that its driver could
>>>> support this DELETE_BUF ioctl() feature.
>>>
>>> Sorry I don't see the link with my patches here...
>>> I have work on non-secure VP9 on stateless codec.
>>> DELETE_BUF ioctl is optional and the main goal is to offer a way to
>>> applications
>>> to save memory if they know when they could delete buffers without 
>>> risk.
>>
>> I try to explain why I think this design in not "complete". One
>> problem resolved, more problems would occur.
>>
>>
>> For non-secure video, those applications have worked:
>>
>> - It would break what stateful means here, application need to
>> acquire(parse) the information that driver should offer.
>>
>>   Or it would break the decoding model.
>>
>> - Your Gstreamer sample code or this design won't work for AV1.
> why ?

A frame in AV1 could be put to display order with a future frame. That 
is quite different to those ITU codecs.

Supposing a frame (we call it frame 0) without show_display frame, you 
could delete it (just want to do that) once it is decoded.

Actually, unless 7 future frames have came and parser has acknowledged 
them, it is not safe to delete that frame.

Or a show_exist that make frame 0 present.

In my personal opinion, this feature could break many uAPI's, I have 
said my worrying in the other emails.
>>
>> For all the future possible secure video:
>>
>> - This feature could never be used from the current design.
>>
>>
>>>
>>>>
>>>>>
>>>>> Regards,
>>>>> Benjamin
>>>>>
>>>>>>
>>>>>>>>>> +       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
>>>>>>>>>>
>>>>>>> -- 
>>>>>>> Hsia-Jun(Randy) Li
>>>>>>>
-- 
Hsia-Jun(Randy) Li

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