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Message-ID: <e08d5d16-3387-ace1-767d-435ab52a98df@collabora.com>
Date:   Mon, 3 Jul 2023 12:35:52 +0200
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Subject: Re: [PATCH v3 10/11] media: v4l2: Add DELETE_BUF ioctl
Content-Language: en-US
To:     Hsia-Jun Li <Randy.Li@synaptics.com>
Cc:     linux-media@vger.kernel.org, linux-kernel@vger.kernel.org,
        p.zabel@pengutronix.de, ming.qian@nxp.com,
        hverkuil-cisco@xs4all.nl, gregkh@linuxfoundation.org,
        ezequiel@vanguardiasur.com.ar,
        linux-arm-kernel@lists.infradead.org,
        linux-mediatek@lists.infradead.org, linux-arm-msm@vger.kernel.org,
        linux-rockchip@lists.infradead.org, nicolas.dufresne@collabora.com,
        linux-staging@lists.linux.dev, kernel@collabora.com,
        mchehab@kernel.org, tfiga@chromium.org, m.szyprowski@samsung.com,
        ayaka <ayaka@soulik.info>
References: <20230622131349.144160-1-benjamin.gaignard@collabora.com>
 <20230622131349.144160-11-benjamin.gaignard@collabora.com>
 <80a03c29-6f3d-43f1-755c-10f3ae2c2756@synaptics.com>
 <42a45bad-09c7-ffb6-49cb-29ec0826599d@collabora.com>
 <3b22fda9-4a0e-2c03-2f12-19e5e3239235@synaptics.com>
 <54833256-7d88-9316-4f0f-b8c57552cd7b@synaptics.com>
 <0f4fd31f-ef61-8dee-7a88-55263f266975@collabora.com>
 <483472c8-74fd-4208-343e-4a8bf79dc6e7@synaptics.com>
 <2b64b605-61cc-248e-a67a-85266434c7a6@collabora.com>
 <16feefaa-e4d9-ad5a-71c5-cee8ce8be5e4@synaptics.com>
From:   Benjamin Gaignard <benjamin.gaignard@collabora.com>
In-Reply-To: <16feefaa-e4d9-ad5a-71c5-cee8ce8be5e4@synaptics.com>
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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@collabora.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 ?
>
> 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
>>>>>>