Re: [PATCH v8 13/53] media: Report the maximum possible number of buffers for the queue
From: Hans Verkuil
Date: Mon Oct 02 2023 - 09:50:18 EST
On 02/10/2023 15:46, Benjamin Gaignard wrote:
>
> Le 02/10/2023 à 15:37, Hans Verkuil a écrit :
>> On 27/09/2023 17:35, Benjamin Gaignard wrote:
>>> Use one of the struct v4l2_create_buffers reserved bytes to report
>>> the maximum possible number of buffers for the queue.
>>> V4l2 framework set V4L2_BUF_CAP_SUPPORTS_SET_MAX_BUFS flags in queue
>>> capabilities so userland can know when the field is valid.
>>>
>>> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@xxxxxxxxxxxxx>
>>> ---
>>> .../userspace-api/media/v4l/vidioc-create-bufs.rst | 8 ++++++--
>>> Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst | 1 +
>>> drivers/media/common/videobuf2/videobuf2-v4l2.c | 9 +++++++--
>>> drivers/media/v4l2-core/v4l2-ioctl.c | 4 ++--
>>> include/uapi/linux/videodev2.h | 7 ++++++-
>>> 5 files changed, 22 insertions(+), 7 deletions(-)
>>>
>>> diff --git a/Documentation/userspace-api/media/v4l/vidioc-create-bufs.rst b/Documentation/userspace-api/media/v4l/vidioc-create-bufs.rst
>>> index a048a9f6b7b6..1a46549e7462 100644
>>> --- a/Documentation/userspace-api/media/v4l/vidioc-create-bufs.rst
>>> +++ b/Documentation/userspace-api/media/v4l/vidioc-create-bufs.rst
>>> @@ -116,9 +116,13 @@ than the number requested.
>>> - ``flags``
>>> - Specifies additional buffer management attributes.
>>> See :ref:`memory-flags`.
>>> -
>>> * - __u32
>>> - - ``reserved``\ [6]
>>> + - ``max_buffers``
>>> + - If V4L2_BUF_CAP_SUPPORTS_SET_MAX_BUFS capability flag is set
>>> + this field indicate the maximum possible number of buffers
>>> + for this queue.
>>> + * - __u32
>>> + - ``reserved``\ [5]
>>> - A place holder for future extensions. Drivers and applications
>>> must set the array to zero.
>>> diff --git a/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst b/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst
>>> index 099fa6695167..0395187e1a5a 100644
>>> --- a/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst
>>> +++ b/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst
>>> @@ -120,6 +120,7 @@ aborting or finishing any DMA in progress, an implicit
>>> .. _V4L2-BUF-CAP-SUPPORTS-ORPHANED-BUFS:
>>> .. _V4L2-BUF-CAP-SUPPORTS-M2M-HOLD-CAPTURE-BUF:
>>> .. _V4L2-BUF-CAP-SUPPORTS-MMAP-CACHE-HINTS:
>>> +.. _V4L2-BUF-CAP-SUPPORTS-SET-MAX-BUFS:
>>> .. raw:: latex
>>> diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c b/drivers/media/common/videobuf2/videobuf2-v4l2.c
>>> index 278ea1107b01..655133f1ae2b 100644
>>> --- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
>>> +++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
>>> @@ -686,6 +686,7 @@ EXPORT_SYMBOL(vb2_querybuf);
>>> static void fill_buf_caps(struct vb2_queue *q, u32 *caps)
>>> {
>>> *caps = V4L2_BUF_CAP_SUPPORTS_ORPHANED_BUFS;
>>> + *caps |= V4L2_BUF_CAP_SUPPORTS_SET_MAX_BUFS;
>>> if (q->io_modes & VB2_MMAP)
>>> *caps |= V4L2_BUF_CAP_SUPPORTS_MMAP;
>>> if (q->io_modes & VB2_USERPTR)
>>> @@ -767,9 +768,13 @@ int vb2_create_bufs(struct vb2_queue *q, struct v4l2_create_buffers *create)
>>> fill_buf_caps(q, &create->capabilities);
>>> validate_memory_flags(q, create->memory, &create->flags);
>>> - create->index = q->num_buffers;
>>> - if (create->count == 0)
>>> +
>>> + create->max_buffers = q->max_num_buffers;
>>> +
>>> + if (create->count == 0) {
>>> + create->index = vb2_get_num_buffers(q);
>> This breaks git bisect: this function isn't introduced until patch 21/53.
>>
>> Note: with the build scripts you can just run it with:
>>
>> ./build.sh -patches 53 ...
>>
>> and it will apply each patch in sequence and attempt to compile it.
>
> It should be create->index = q->num_buffers;
> The error is also in v9...
Sorry, I meant to reply to the v9 patch, so yes, it is also in v9 :-)
Hans
>
>>
>> Regards,
>>
>> Hans
>>
>>> return ret != -EBUSY ? ret : 0;
>>> + }
>>> switch (f->type) {
>>> case V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE:
>>> diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c
>>> index f4d9d6279094..700db197e371 100644
>>> --- a/drivers/media/v4l2-core/v4l2-ioctl.c
>>> +++ b/drivers/media/v4l2-core/v4l2-ioctl.c
>>> @@ -483,9 +483,9 @@ static void v4l_print_create_buffers(const void *arg, bool write_only)
>>> {
>>> const struct v4l2_create_buffers *p = arg;
>>> - pr_cont("index=%d, count=%d, memory=%s, capabilities=0x%08x, ",
>>> + pr_cont("index=%d, count=%d, memory=%s, capabilities=0x%08x, max buffers=%u",
>>> p->index, p->count, prt_names(p->memory, v4l2_memory_names),
>>> - p->capabilities);
>>> + p->capabilities, p->max_buffers);
>>> v4l_print_format(&p->format, write_only);
>>> }
>>> diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
>>> index 78260e5d9985..b0dbb1be728c 100644
>>> --- a/include/uapi/linux/videodev2.h
>>> +++ b/include/uapi/linux/videodev2.h
>>> @@ -1034,6 +1034,7 @@ struct v4l2_requestbuffers {
>>> #define V4L2_BUF_CAP_SUPPORTS_ORPHANED_BUFS (1 << 4)
>>> #define V4L2_BUF_CAP_SUPPORTS_M2M_HOLD_CAPTURE_BUF (1 << 5)
>>> #define V4L2_BUF_CAP_SUPPORTS_MMAP_CACHE_HINTS (1 << 6)
>>> +#define V4L2_BUF_CAP_SUPPORTS_SET_MAX_BUFS (1 << 7)
>>> /**
>>> * struct v4l2_plane - plane info for multi-planar buffers
>>> @@ -2604,6 +2605,9 @@ struct v4l2_dbg_chip_info {
>>> * @flags: additional buffer management attributes (ignored unless the
>>> * queue has V4L2_BUF_CAP_SUPPORTS_MMAP_CACHE_HINTS capability
>>> * and configured for MMAP streaming I/O).
>>> + * @max_buffers: if V4L2_BUF_CAP_SUPPORTS_SET_MAX_BUFS capability flag is set
>>> + * this field indicate the maximum possible number of buffers
>>> + * for this queue.
>>> * @reserved: future extensions
>>> */
>>> struct v4l2_create_buffers {
>>> @@ -2613,7 +2617,8 @@ struct v4l2_create_buffers {
>>> struct v4l2_format format;
>>> __u32 capabilities;
>>> __u32 flags;
>>> - __u32 reserved[6];
>>> + __u32 max_buffers;
>>> + __u32 reserved[5];
>>> };
>>> /*
>>