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

Ming Qian
2023-06-26T08:04:25Z

>-----Original Message-----
>From: Benjamin Gaignard <benjamin.gaignard@collabora.com>
>Sent: 2023年6月26日 15:49
>To: Ming Qian <ming.qian@nxp.com>; mchehab@kernel.org;
>tfiga@chromium.org; m.szyprowski@samsung.com;
>ezequiel@vanguardiasur.com.ar; p.zabel@pengutronix.de;
>gregkh@linuxfoundation.org; hverkuil-cisco@xs4all.nl;
>nicolas.dufresne@collabora.com
>Cc: linux-media@vger.kernel.org; linux-kernel@vger.kernel.org; linux-arm-
>kernel@lists.infradead.org; linux-mediatek@lists.infradead.org; linux-arm-
>msm@vger.kernel.org; linux-rockchip@lists.infradead.org; linux-
>staging@lists.linux.dev; kernel@collabora.com
>Subject: Re: [EXT] [PATCH v3 10/11] media: v4l2: Add DELETE_BUF ioctl
>
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>
>Le 26/06/2023 à 09:08, Ming Qian a écrit :
>> Hi Benjamin,
>>
>>> -----Original Message-----
>>> From: Benjamin Gaignard <benjamin.gaignard@collabora.com>
>>> Sent: 2023年6月22日 21:14
>>> To: mchehab@kernel.org; tfiga@chromium.org;
>m.szyprowski@samsung.com;
>>> Ming Qian <ming.qian@nxp.com>; ezequiel@vanguardiasur.com.ar;
>>> p.zabel@pengutronix.de; gregkh@linuxfoundation.org; hverkuil-
>>> cisco@xs4all.nl; nicolas.dufresne@collabora.com
>>> Cc: linux-media@vger.kernel.org; linux-kernel@vger.kernel.org;
>>> linux-arm- kernel@lists.infradead.org;
>>> linux-mediatek@lists.infradead.org; linux-arm- msm@vger.kernel.org;
>>> linux-rockchip@lists.infradead.org; linux- staging@lists.linux.dev;
>>> kernel@collabora.com; Benjamin Gaignard
>>> <benjamin.gaignard@collabora.com>
>>> Subject: [EXT] [PATCH v3 10/11] media: v4l2: Add DELETE_BUF ioctl
>>>
>>> Caution: This is an external email. Please take care when clicking
>>> links or opening attachments. When in doubt, report the message using
>>> the 'Report this email' button
>>>
>>>
>>> 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;
>>> + }
>>> +
>>> + 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);
>> The num_buffers is not changed, Is that on purpose?
>> num_buffers doesn't mean the number of vb2 buffers, but only decides the
>max index of allocated vb2 buffer?
>> Once the index is deleted, then it won't be used anymore, unless free the
>vb2 queue? is it a hole in vb2 queue?
>
>Yes num_buffers isn't change and still represent the highest index of allocated
>buffer.
>DELETE_BUF remove the buffer from the list and free the memory.
>That could a create a hole in vb2 queue, that why the first patch of this series
>change all places where vb2 queue array was used by calls to helpers function
>and also check the return value.
>num_buffers is used as the lowest possible value when finding the free
>indexes for buffers (see vb2_queue_add_buffer()) this way I can guaranty that
>the indexes a continuous which is a requirement for create_bufs.
>I choose this solution because XArray API doesn't offer way to find continuous
>free range.
>It doesn't seem impossible to add it but this series is already big enough from
>my point of view.
>

Thank you for your detailed explanation.

>Regards,
>Benjamin
>
>>
>> And you can use xa_for_each() instead the for loop to iterate over the
>present buffers in vb2 queue.
>>
>>> +
>>> + 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