Message-ID: <ecdc5625-f18a-2fc3-6f85-381f84bbfb1b@soulik.info>
Date:   Mon, 3 Jul 2023 23:42:34 +0800
From:   Randy Li <ayaka@...lik.info>
To:     Benjamin Gaignard <benjamin.gaignard@...labora.com>
Cc:     linux-media@...r.kernel.org, Hsia-Jun Li <Randy.Li@...aptics.com>,
        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
Subject: Re: [PATCH v3 10/11] media: v4l2: Add DELETE_BUF ioctl


On 2023/7/3 19:17, Benjamin Gaignard wrote:
>
> Le 03/07/2023 à 13:02, Hsia-Jun Li a écrit :
>>
>>
>> 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.
>>
> Of course if the application delete a useful buffer it is a problem 
> but an application issue.

I don't think this feature is only applied to stateless codec. Stateful 
codec could reclaim the previous memory as well.

The implementation now just leave all those problems to the conscience 
of the application, no protection from the kernel which could crash the 
hardware easily.

I am not against  on this feature, I just wish it would be more safe and 
more complete.

> I have test this code using GStreamer with VP9, VP8 and HEVC on 
> Verisilicon driver without issues.

Even with the secure decoding, at least someone should offer the DPB 
info or we just don't need this.

I am sure stateless decoder could work well with that despite the 
performance impact on buffer looking up.

>
> I will be happy if someone could test it on another driver and/or 
> other userlands (like ffmpeg).
>
>>>>
>>>> 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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