Hi Benjamin,
On 05/09/2023 16:28, Benjamin Gaignard wrote:
>
> Le 05/09/2023 à 10:17, Hans Verkuil a écrit :
>> On 01/09/2023 14:44, Benjamin Gaignard wrote:
>>> VIDIOC_DELETE_BUFS ioctl allows to delete buffers from a queue.
>>> The number of buffers to delete in given by count field of
>>> struct v4l2_delete_buffers and the range start at the index
>>> specified in the same structure.
>>>
>>> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@xxxxxxxxxxxxx>
>>> ---
>>> v6:
>>> - Add lock in vb2_core_delete_buf()
>>> - Fix typo and comments
>>> - Add flags in VIDIOC_DELETE_BUFS decalaration
>>>
>>> .../userspace-api/media/v4l/user-func.rst | 1 +
>>> .../media/v4l/vidioc-delete-bufs.rst | 73 +++++++++++++++++++
>>> .../media/common/videobuf2/videobuf2-core.c | 24 ++++++
>>> .../media/common/videobuf2/videobuf2-v4l2.c | 38 +++++++++-
>>> drivers/media/v4l2-core/v4l2-dev.c | 1 +
>>> drivers/media/v4l2-core/v4l2-ioctl.c | 17 +++++
>>> include/media/v4l2-ioctl.h | 4 +
>>> include/media/videobuf2-core.h | 9 +++
>>> include/media/videobuf2-v4l2.h | 11 +++
>>> include/uapi/linux/videodev2.h | 16 ++++
>>> 10 files changed, 193 insertions(+), 1 deletion(-)
>>> create mode 100644 Documentation/userspace-api/media/v4l/vidioc-delete-bufs.rst
>>>
>>> diff --git a/Documentation/userspace-api/media/v4l/user-func.rst b/Documentation/userspace-api/media/v4l/user-func.rst
>>> index 15ff0bf7bbe6..3fd567695477 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-bufs
>>> vidioc-dqevent
>>> vidioc-dv-timings-cap
>>> vidioc-encoder-cmd
>>> diff --git a/Documentation/userspace-api/media/v4l/vidioc-delete-bufs.rst b/Documentation/userspace-api/media/v4l/vidioc-delete-bufs.rst
>>> new file mode 100644
>>> index 000000000000..a55fe6331fc8
>>> --- /dev/null
>>> +++ b/Documentation/userspace-api/media/v4l/vidioc-delete-bufs.rst
>>> @@ -0,0 +1,73 @@
>>> +.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
>>> +.. c:namespace:: V4L
>>> +
>>> +.. _VIDIOC_DELETE_BUFS:
>>> +
>>> +************************
>>> +ioctl VIDIOC_DELETE_BUFS
>>> +************************
>>> +
>>> +Name
>>> +====
>>> +
>>> +VIDIOC_DELETE_BUFS - Deletes buffers from a queue
>>> +
>>> +Synopsis
>>> +========
>>> +
>>> +.. c:macro:: VIDIOC_DELETE_BUFs
>>> +
>>> +``int ioctl(int fd, VIDIOC_DELETE_BUFs, struct v4l2_delete_buffers *argp)``
>>> +
>>> +Arguments
>>> +=========
>>> +
>>> +``fd``
>>> + File descriptor returned by :c:func:`open()`.
>>> +
>>> +``argp``
>>> + Pointer to struct :c:type:`v4l2_delete_buffers`.
>>> +
>>> +Description
>>> +===========
>>> +
>>> +Applications can optionally call the :ref:`VIDIOC_DELETE_BUFS` ioctl to
>>> +delete buffers from a queue.
>>> +
>>> +.. c:type:: v4l2_delete_buffers
>>> +
>>> +.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.5cm}|
>>> +
>>> +.. flat-table:: struct v4l2_delete_buffers
>>> + :header-rows: 0
>>> + :stub-columns: 0
>>> + :widths: 1 1 2
>>> +
>>> + * - __u32
>>> + - ``index``
>>> + - The starting buffer index to delete.
>>> + * - __u32
>>> + - ``count``
>>> + - The number of buffers to be deleted.
>> That's not quite correct. This function will delete the buffers with indices
>> index until index+count-1. And indices in that range have to be valid buffers,
>> i.e. you can't have already deleted buffers in that range.
>>
>> Or should we allow that? It is a fair question.
>>
>> All buffers also have to be in the DEQUEUED state.
>>
>> The text above suggests that given the following valid indices:
>>
>> 0, 1, 3, 4 (so the buffer with index 2 was already deleted)
>>
>> deleting 2 buffers from index 1 would delete buffers 1, 3. When in
>> fact it will attempt to delete buffers 1 and 2.
>>
>> Also document explicitly that calling this with count=0 (and perhaps
>> index=0 as well?) can be used to check if this ioctl is supported.
>
> I will do that.
>
>>
>>> + * - __u32
>>> + - ``type``
>>> + - Type of the stream or buffers, this is the same as the struct
>>> + :c:type:`v4l2_format` ``type`` field. See
>>> + :c:type:`v4l2_buf_type` for valid values.
>>> + * - __u32
>>> + - ``reserved``\ [13]
>>> + - A place holder for future extensions. Drivers and applications
>>> + must set the array to zero.
>> What should happen if you delete ALL buffers with this call? I.e., the
>> equivalent to REQBUFS with count=0.
>>
>> Thinking about this the main difference is that DELETE_BUFS can only delete
>> dequeued buffers and it does not stop streaming if all buffers are deleted.
>>
>> So REQBUFS with count=0 (or a STREAMOFF) is still needed to officially stop
>> streaming and cancel the queue.
>>
>> Basically REQBUFS with count=0 is almost the equivalent of calling STREAMOFF followed
>> by DELETE_BUFS for all buffers. Almost, but not quite: REQBUFS(0) also reports
>> if the queue is unbalanced, and it sets q->num_buffers to 0. And in vb2_ioctl_reqbufs
>> it will set vdev->queue->owner to NULL.
>>
>> I am inclined to do the same if DELETE_BUFS deletes all buffers.
>
> Unlike REQBUFS DELETE_BUFS can delete buffers while streaming so for me the ownership
> should not change even if there is no more dequeued buffers.
> For REQBUFS with count=0 means that the going stream is stopped so we can delete all the buffers
> while DELETE_BUFS usage is to delete buffers while keeping the stream alive.
I'm undecided on this. It's something we can decide later.
>
>>
>>> +
>>> +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 dc7f6b59d237..9edb2a1e95fc 100644
>>> --- a/drivers/media/common/videobuf2/videobuf2-core.c
>>> +++ b/drivers/media/common/videobuf2/videobuf2-core.c
>>> @@ -1633,6 +1633,30 @@ int vb2_core_prepare_buf(struct vb2_queue *q, struct vb2_buffer *vb, void *pb)
>>> }
>>> EXPORT_SYMBOL_GPL(vb2_core_prepare_buf);
>>> +int vb2_core_delete_buf(struct vb2_queue *q, struct vb2_buffer *vb)
>>> +{
>>> + mutex_lock(&q->mmap_lock);
>>> + 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);
>>> + mutex_unlock(&q->mmap_lock);
>>> +
>>> + dprintk(q, 2, "buffer %d deleted\n", vb->index);
>>> + kfree(vb);
>>> +
>>> + return 0;
>>> +}
>>> +EXPORT_SYMBOL_GPL(vb2_core_delete_buf);
>> This is duplicating what already happens in __vb2_free_mem and __vb2_queue_free.
>>
>> That code needs to be refactored.
>>
>> What you want is a __vb2_delete_buffers(struct vb2_queue *q, unsigned int index, unsigned int buffers)
>> function that is called with mmap_lock held and that deletes buffers in the range 'index'
>> to 'index + count - 1'. Buffers may already be deleted.
>>
>> __vb2_free_mem does almost do all of that already.
>>
>> Then this new function can be called from __vb2_queue_free() and you can make
>> a vb2_core_delete_bufs() function that takes the lock and calls __vb2_delete_buffers.
>>
>> Another note: currently __vb2_queue_free checks if any of the buffers had unbalanced
>> operations. That check needs to be moved to __vb2_delete_buffers as well otherwise
>> that would never be reported when using DELETE_BUFS.
>
> Loops in __vb2_queue_free() and __vb2_free_mem() try to delete buffers at the end of the
> queue, I could just modify these functions prototype and loops to start from a given index.
> That should do the job but have impact on create_bufs (see below)
>
>>
>>> +
>>> /*
>>> * 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 8ba658ad9891..d0098f58a65c 100644
>>> --- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
>>> +++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
>>> @@ -385,7 +385,7 @@ static int vb2_queue_or_prepare_buf(struct vb2_queue *q, struct media_device *md
>>> vb = vb2_get_buffer(q, b->index);
>>> if (!vb) {
>>> - dprintk(q, 1, "%s: buffer is NULL\n", opname);
>>> + dprintk(q, 1, "%s: buffer %u was deleted\n", opname, b->index);
>>> return -EINVAL;
>>> }
>>> @@ -757,6 +757,42 @@ int vb2_prepare_buf(struct vb2_queue *q, struct media_device *mdev,
>>> }
>>> EXPORT_SYMBOL_GPL(vb2_prepare_buf);
>>> +int vb2_delete_bufs(struct vb2_queue *q, struct v4l2_delete_buffers *d)
>>> +{
>>> + struct vb2_buffer *vb;
>>> + unsigned int index;
>>> + int ret = 0;
>>> +
>> Add:
>>
>> if (!d->count)
>> return 0;
>>
>> (possibly also check if !d->index)
>>
>>> + if (d->index > q->num_buffers ||
>>> should be >= here.
>>> + d->count > q->num_buffers ||
>>> + (d->index + d->count) > q->num_buffers) {
>>> + return -EINVAL;
>>> + }
>> Once we can delete buffers, how does that change the meaning of num_buffers?
>> Isn't this really max_buffer_index or something similar? But we probably also
>> still need to keep track of the actual number of buffers.
>>
>> And create_bufs still allocated buffers from the last index onwards, it does
>> not attempt to reuse indices of previously deleted buffers.
>
> Reuse previous indices require to be sure that a range of index is free because
> create_bufs returns, in index parameter, the starting buffer index.
> I will add a function to find the first available range and use it in vb2_create_bufs()
> to change how create->index is set.
> Hans, sound good for you ?
That's what I had in mind. It is an option to keep a bitmap to keep track
of which buffer indices are in use. You could use bitmap_find_next_zero_area
to find the free range.
Just an option.
>
>>
>> There are a lot of drivers that use num_buffers, they will have to be audited.
>>
>> This needs a lot more thought.
>>
>>> +
>>> + for (index = d->index; index < d->index + d->count; index++) {
>>> + vb = vb2_get_buffer(q, index);
>>> + if (!vb) {
>>> + dprintk(q, 1, "can't find the requested buffer\n");
>>> + ret = -EINVAL;
>>> + goto error;
>>> + }
>>> + if (vb->state != VB2_BUF_STATE_DEQUEUED) {
>>> + dprintk(q, 1, "can't delete non dequeued buffer index %d\n", vb->index);
>>> + ret = -EINVAL;
>>> + goto error;
>>> + }
>> These checks have to take place first, then, if all is OK, you call vb2_core_delete_bufs.
>>
>> Actually, thinking this over, I would move all these checks to vb2_core_delete_bufs.
>>
>> It can all be put under the mmap_lock mutex to ensure nobody is messing around
>> with the queue while this takes place.
>>
>> Note that when vb2_core_reqbufs() is called with count=0, then if it sees that
>> a buffer is still in use (mmaped), it will log a debug message that the buffers
>> are orphaned. We should keep that, I believe.
>>
>>> +
>>> + ret = vb2_core_delete_buf(q, vb);
>>> + if (ret)
>>> + break;
>>> + }
>>> +
>>> +error:
>>> + d->index = index;
>> I wouldn't do this. I don't think this is useful.
>>
>>> + return ret;
>>> +}
>>> +EXPORT_SYMBOL_GPL(vb2_delete_bufs);
>>> +
>>> 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..215654fd6581 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_BUFS, vidioc_delete_bufs);
>>> }
>>> 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 f4d9d6279094..aac3a0ea0126 100644
>>> --- a/drivers/media/v4l2-core/v4l2-ioctl.c
>>> +++ b/drivers/media/v4l2-core/v4l2-ioctl.c
>>> @@ -489,6 +489,13 @@ static void v4l_print_create_buffers(const void *arg, bool write_only)
>>> v4l_print_format(&p->format, write_only);
>>> }
>>> +static void v4l_print_delete_buffers(const void *arg, bool write_only)
>>> +{
>>> + const struct v4l2_delete_buffers *p = arg;
>>> +
>>> + pr_cont("index=%d, count=%d\n", p->index, p->count);
>> Use %u since both args are unsigned.
>>
>>> +}
>>> +
>>> static void v4l_print_streamparm(const void *arg, bool write_only)
>>> {
>>> const struct v4l2_streamparm *p = arg;
>>> @@ -2160,6 +2167,15 @@ 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_bufs(const struct v4l2_ioctl_ops *ops,
>>> + struct file *file, void *fh, void *arg)
>>> +{
>>> + struct v4l2_delete_buffers *delete = arg;
>>> + int ret = check_fmt(file, delete->type);
>>> +
>>> + return ret ? ret : ops->vidioc_delete_bufs(file, fh, delete);
>>> +}
>>> +
>>> static int v4l_g_parm(const struct v4l2_ioctl_ops *ops,
>>> struct file *file, void *fh, void *arg)
>>> {
>>> @@ -2909,6 +2925,7 @@ 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_BUFS, v4l_delete_bufs, v4l_print_delete_buffers, INFO_FL_PRIO | INFO_FL_QUEUE | INFO_FL_CLEAR(v4l2_delete_buffers, type)),
>>> };
>>> #define V4L2_IOCTLS ARRAY_SIZE(v4l2_ioctls)
>>> diff --git a/include/media/v4l2-ioctl.h b/include/media/v4l2-ioctl.h
>>> index edb733f21604..55afbde54211 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_bufs: pointer to the function that implements
>>> + * :ref:`VIDIOC_DELETE_BUFS <vidioc_delete_bufs>` 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_bufs)(struct file *file, void *fh,
>>> + struct v4l2_delete_buffers *d);
>>> 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 97153c69583f..e2c5ff31efd0 100644
>>> --- a/include/media/videobuf2-core.h
>>> +++ b/include/media/videobuf2-core.h
>>> @@ -843,6 +843,15 @@ int vb2_core_create_bufs(struct vb2_queue *q, enum vb2_memory memory,
>>> */
>>> int vb2_core_prepare_buf(struct vb2_queue *q, struct vb2_buffer *vb, void *pb);
>>> +/**
>>> + * vb2_core_delete_buf() -
>>> + * @q: pointer to &struct vb2_queue with videobuf2 queue.
>>> + * @vb: pointer to struct &vb2_buffer.
>>> + *
>>> + * Return: returns zero on success; an error code otherwise.
>>> + */
>>> +int vb2_core_delete_buf(struct vb2_queue *q, struct vb2_buffer *vb);
>>> +
>>> /**
>>> * vb2_core_qbuf() - Queue a buffer from userspace
>>> *
>>> diff --git a/include/media/videobuf2-v4l2.h b/include/media/videobuf2-v4l2.h
>>> index 5a845887850b..2ef68fdf388f 100644
>>> --- a/include/media/videobuf2-v4l2.h
>>> +++ b/include/media/videobuf2-v4l2.h
>>> @@ -118,6 +118,17 @@ 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_bufs() - Delete buffers from the queue
>>> + *
>>> + * @q: pointer to &struct vb2_queue with videobuf2 queue.
>>> + * @d: delete parameter, passed from userspace to
>>> + * &v4l2_ioctl_ops->vidioc_delete_bufs handler in driver
>>> + *
>>> + * The return values from this function are intended to be directly returned
>>> + * from &v4l2_ioctl_ops->vidioc_delete_bufs handler in driver.
>>> + */
>>> +int vb2_delete_bufs(struct vb2_queue *q, struct v4l2_delete_buffers *d);
>> I'm missing the vb2_ioctl_delete_bufs function with a call to vb2_queue_is_busy().
>>
>>> /**
>>> * vb2_qbuf() - Queue a buffer from userspace
>>> diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
>>> index 78260e5d9985..9cc7f570d995 100644
>>> --- a/include/uapi/linux/videodev2.h
>>> +++ b/include/uapi/linux/videodev2.h
>>> @@ -2616,6 +2616,20 @@ struct v4l2_create_buffers {
>>> __u32 reserved[6];
>>> };
>>> +/**
>>> + * struct v4l2_delete_buffers - VIDIOC_DELETE_BUFS argument
>>> + * @index: the first buffer to be deleted
>>> + * @count: number of buffers to delete
>>> + * @type: enum v4l2_buf_type
>>> + * @reserved: future extensions
>>> + */
>>> +struct v4l2_delete_buffers {
>>> + __u32 index;
>>> + __u32 count;
>>> + __u32 type;
>>> + __u32 reserved[13];
>>> +};
>>> +
>>> /*
>>> * I O C T L C O D E S F O R V I D E O D E V I C E S
>>> *
>>> @@ -2715,6 +2729,8 @@ 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_BUFS _IOWR('V', 104, struct v4l2_delete_buffers)
>>> +
>>> /* Reminder: when adding new ioctls please add support for them to
>>> drivers/media/v4l2-core/v4l2-compat-ioctl32.c as well! */
>> You need much more extensive compliance checks for this, esp. mixing
>> create_bufs and delete_bufs. And test it with the test-media test script.
>>
>> Regards,
>>
>> Hans
>>
Regards,
Hans
