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Message-ID: <CAAFQd5BkKQS_PZ6HNCNdq3T7oWC_=cVGhX852P1d0DE_TJ_dMA@mail.gmail.com>
Date: Tue, 15 Dec 2020 18:03:04 +0900
From: Tomasz Figa <tfiga@...omium.org>
To: Helen Koike <helen.koike@...labora.com>
Cc: Mauro Carvalho Chehab <mchehab@...nel.org>,
Hans Verkuil <hans.verkuil@...co.com>,
Laurent Pinchart <laurent.pinchart@...asonboard.com>,
Sakari Ailus <sakari.ailus@....fi>,
Linux Media Mailing List <linux-media@...r.kernel.org>,
Boris Brezillon <boris.brezillon@...labora.com>,
Hirokazu Honda <hiroh@...omium.org>,
Nicolas Dufresne <nicolas@...fresne.ca>,
Brian Starkey <Brian.Starkey@....com>, kernel@...labora.com,
Neil Armstrong <narmstrong@...libre.com>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Fritz Koenig <frkoenig@...omium.org>,
Maxime Jourdan <mjourdan@...libre.com>,
Stanimir Varbanov <stanimir.varbanov@...aro.org>
Subject: Re: [PATCH v5 2/7] media: v4l2: Add extended buffer operations
On Mon, Dec 14, 2020 at 10:24 PM Helen Koike <helen.koike@...labora.com> wrote:
>
> Hi Tomasz,
>
> Thank you for your comments,
>
> On 12/14/20 7:36 AM, Tomasz Figa wrote:
> > On Tue, Nov 24, 2020 at 5:33 AM Helen Koike <helen.koike@...labora.com> wrote:
> >>
> >> Hi Tomasz,
> >>
> >>
> >> On 11/20/20 8:14 AM, Tomasz Figa wrote:
> >>> Hi Helen,
> >>>
> >>> On Tue, Aug 04, 2020 at 04:29:34PM -0300, Helen Koike wrote:
> >>>> From: Hans Verkuil <hans.verkuil@...co.com>
> >>>>
> >>>> Those extended buffer ops have several purpose:
> >>>> 1/ Fix y2038 issues by converting the timestamp into an u64 counting
> >>>> the number of ns elapsed since 1970
> >>>> 2/ Unify single/multiplanar handling
> >>>> 3/ Add a new start offset field to each v4l2 plane buffer info struct
> >>>> to support the case where a single buffer object is storing all
> >>>> planes data, each one being placed at a different offset
> >>>>
> >>>> New hooks are created in v4l2_ioctl_ops so that drivers can start using
> >>>> these new objects.
> >>>>
> >>>> The core takes care of converting new ioctls requests to old ones
> >>>> if the driver does not support the new hooks, and vice versa.
> >>>>
> >>>> Note that the timecode field is gone, since there doesn't seem to be
> >>>> in-kernel users. We can be added back in the reserved area if needed or
> >>>> use the Request API to collect more metadata information from the
> >>>> frame.
> >>>>
> >>>
> >>> Thanks for the patch. Please see my comments inline.
> >>
> >> Thank you for your detailed review, please see my comments below.
> >>
> >>>
> >>>> Signed-off-by: Hans Verkuil <hans.verkuil@...co.com>
> >>>> Signed-off-by: Boris Brezillon <boris.brezillon@...labora.com>
> >>>> Signed-off-by: Helen Koike <helen.koike@...labora.com>
> >>>> ---
> >>>> Changes in v5:
> >>>> - migrate memory from v4l2_ext_buffer to v4l2_ext_plane
> >>>> - return mem_offset to struct v4l2_ext_plane
> >>>> - change sizes and reorder fields to avoid holes in the struct and make
> >>>> it the same for 32 and 64 bits
> >>>>
> >>>> Changes in v4:
> >>>> - Use v4l2_ext_pix_format directly in the ioctl, drop v4l2_ext_format,
> >>>> making V4L2_BUF_TYPE_VIDEO_[OUTPUT,CAPTURE] the only valid types.
> >>>> - Drop VIDIOC_EXT_EXPBUF, since the only difference from VIDIOC_EXPBUF
> >>>> was that with VIDIOC_EXT_EXPBUF we could export multiple planes at once.
> >>>> I think we can add this later, so I removed it from this RFC to simplify it.
> >>>> - Remove num_planes field from struct v4l2_ext_buffer
> >>>> - Add flags field to struct v4l2_ext_create_buffers
> >>>> - Reformulate struct v4l2_ext_plane
> >>>> - Fix some bugs caught by v4l2-compliance
> >>>> - Rebased on top of media/master (post 5.8-rc1)
> >>>>
> >>>> Changes in v3:
> >>>> - Rebased on top of media/master (post 5.4-rc1)
> >>>>
> >>>> Changes in v2:
> >>>> - Add reserved space to v4l2_ext_buffer so that new fields can be added
> >>>> later on
> >>>> ---
> >>>> drivers/media/v4l2-core/v4l2-dev.c | 29 ++-
> >>>> drivers/media/v4l2-core/v4l2-ioctl.c | 353 +++++++++++++++++++++++++--
> >>>> include/media/v4l2-ioctl.h | 26 ++
> >>>> include/uapi/linux/videodev2.h | 90 +++++++
> >>>> 4 files changed, 476 insertions(+), 22 deletions(-)
> >>>>
> >>>> diff --git a/drivers/media/v4l2-core/v4l2-dev.c b/drivers/media/v4l2-core/v4l2-dev.c
> >>>> index e1829906bc086..cb21ee8eb075c 100644
> >>>> --- a/drivers/media/v4l2-core/v4l2-dev.c
> >>>> +++ b/drivers/media/v4l2-core/v4l2-dev.c
> >>>> @@ -720,15 +720,34 @@ static void determine_valid_ioctls(struct video_device *vdev)
> >>>> SET_VALID_IOCTL(ops, VIDIOC_TRY_FMT, vidioc_try_fmt_sdr_out);
> >>>> }
> >>>>
> >>>> + if (is_vid || is_tch) {
> >>>> + /* ioctls valid for video and touch */
> >>>> + if (ops->vidioc_querybuf || ops->vidioc_ext_querybuf)
> >>>> + set_bit(_IOC_NR(VIDIOC_EXT_QUERYBUF), valid_ioctls);
> >>>> + if (ops->vidioc_qbuf || ops->vidioc_ext_qbuf)
> >>>> + set_bit(_IOC_NR(VIDIOC_EXT_QBUF), valid_ioctls);
> >>>> + if (ops->vidioc_dqbuf || ops->vidioc_ext_dqbuf)
> >>>> + set_bit(_IOC_NR(VIDIOC_EXT_DQBUF), valid_ioctls);
> >>>> + if (ops->vidioc_create_bufs || ops->vidioc_ext_create_bufs)
> >>>> + set_bit(_IOC_NR(VIDIOC_EXT_CREATE_BUFS), valid_ioctls);
> >>>> + if (ops->vidioc_prepare_buf || ops->vidioc_ext_prepare_buf)
> >>>> + set_bit(_IOC_NR(VIDIOC_EXT_PREPARE_BUF), valid_ioctls);
> >>>
> >>> nit: Could we stick to the SET_VALID_IOCTL() macro and just call it twice,
> >>> once for the new and once for the legacy callback?
> >>
> >> Ack.
> >>
> >>>
> >>>> + }
> >>>> +
> >>>> if (is_vid || is_vbi || is_sdr || is_tch || is_meta) {
> >>>> /* ioctls valid for video, vbi, sdr, touch and metadata */
> >>>> SET_VALID_IOCTL(ops, VIDIOC_REQBUFS, vidioc_reqbufs);
> >>>> - SET_VALID_IOCTL(ops, VIDIOC_QUERYBUF, vidioc_querybuf);
> >>>> - SET_VALID_IOCTL(ops, VIDIOC_QBUF, vidioc_qbuf);
> >>>> SET_VALID_IOCTL(ops, VIDIOC_EXPBUF, vidioc_expbuf);
> >>>> - SET_VALID_IOCTL(ops, VIDIOC_DQBUF, vidioc_dqbuf);
> >>>> - SET_VALID_IOCTL(ops, VIDIOC_CREATE_BUFS, vidioc_create_bufs);
> >>>> - SET_VALID_IOCTL(ops, VIDIOC_PREPARE_BUF, vidioc_prepare_buf);
> >>>> + if (ops->vidioc_querybuf || ops->vidioc_ext_querybuf)
> >>>> + set_bit(_IOC_NR(VIDIOC_QUERYBUF), valid_ioctls);
> >>>> + if (ops->vidioc_qbuf || ops->vidioc_ext_qbuf)
> >>>> + set_bit(_IOC_NR(VIDIOC_QBUF), valid_ioctls);
> >>>> + if (ops->vidioc_dqbuf || ops->vidioc_ext_dqbuf)
> >>>> + set_bit(_IOC_NR(VIDIOC_DQBUF), valid_ioctls);
> >>>> + if (ops->vidioc_create_bufs || ops->vidioc_ext_create_bufs)
> >>>> + set_bit(_IOC_NR(VIDIOC_CREATE_BUFS), valid_ioctls);
> >>>> + if (ops->vidioc_prepare_buf || ops->vidioc_ext_prepare_buf)
> >>>> + set_bit(_IOC_NR(VIDIOC_PREPARE_BUF), valid_ioctls);
> >>>
> >>> Is it valid to check the new callbacks for devices that the new API is not
> >>> valid for (e.g. vbi)? Perhaps we could call SET_VALID_IOCTL(ops, <ioctl>,
> >>> vidioc_ext_*) in the upper if added in this patch and keep the code above
> >>> as is?
> >>
> >> Just to be clear, the only valid type should be VFL_TYPE_VIDEO right?
> >> Ext but API won't support touch devices for instance, right?
> >>
> >
> > Yes, at least at this point. If one needs, it could be added in the
> > future, but honestly I don't see much use of the other types these
> > days.
>
> Ok, I already updated this in my wip branch for next version.
>
> >
> >>
> >>>
> >>>> SET_VALID_IOCTL(ops, VIDIOC_STREAMON, vidioc_streamon);
> >>>> SET_VALID_IOCTL(ops, VIDIOC_STREAMOFF, vidioc_streamoff);
> >>>> }
> >>>> diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c
> >>>> index 14a0def50f8ea..7ecdd9cc1bf48 100644
> >>>> --- a/drivers/media/v4l2-core/v4l2-ioctl.c
> >>>> +++ b/drivers/media/v4l2-core/v4l2-ioctl.c
> >>>> @@ -527,6 +527,26 @@ static void v4l_print_buffer(const void *arg, bool write_only)
> >>>> tc->type, tc->flags, tc->frames, *(__u32 *)tc->userbits);
> >>>> }
> >>>>
> >>>> +static void v4l_print_ext_buffer(const void *arg, bool write_only)
> >>>> +{
> >>>> + const struct v4l2_ext_buffer *e = arg;
> >>>> + const struct v4l2_ext_plane *plane;
> >>>> + unsigned int i;
> >>>> +
> >>>> + pr_cont("%lld index=%d, type=%s, flags=0x%08x, field=%s, sequence=%d\n",
> >>>> + e->timestamp, e->index, prt_names(e->type, v4l2_type_names),
> >>>> + e->flags, prt_names(e->field, v4l2_field_names), e->sequence);
> >>>
> >>> Should we also print the request FD?
> >>
> >> Yes, I'll update this for next version.
> >>
> >>>
> >>>> +
> >>>> + for (i = 0; i < VIDEO_MAX_PLANES &&
> >>>> + e->planes[i].buffer_length; i++) {
> >>>> + plane = &e->planes[i];
> >>>> + pr_debug("plane %d: buffer_length=%d, plane_length=%d offset=0x%08x, memory=%s\n",
> >>>> + i, plane->buffer_length, plane->plane_length,
> >>>> + plane->offset,
> >>>> + prt_names(plane->memory, v4l2_memory_names));
> >>>
> >>> Should we also print mem_offset/userptr/dmabuf_fd?
> >>
> >> I see they are not printed by v4l_print_buffer(),
> >
> > offset/userptr are printed in v4l2_print_buffer:
> > https://elixir.bootlin.com/linux/latest/source/drivers/media/v4l2-core/v4l2-ioctl.c#L494
>
> yes, sorry about that, I saw this later and I already updated it for next version.
>
> >
> >> since these fields are in an
> >> union, the value of two of them will be invalid (I wonder if this can bring
> >> confusion).
> >> I also wondered if printing them can't cause a security issue.
> >>
> >> But I can add those prints if you think it make sense.
> >>
> >
> > We know the memory type, so we can interpret the union appropriately
> > and adjust the message printed.
> >
> > I don't think this poses any security issue, as it prints things that
> > belong to the userspace already and are only meaningful in the context
> > of the given userspace process.
>
> ok.
>
> >
> >>>
> >>>> + }
> >>>> +}
> >>>> +
> >>>> static void v4l_print_exportbuffer(const void *arg, bool write_only)
> >>>> {
> >>>> const struct v4l2_exportbuffer *p = arg;
> >>>> @@ -546,6 +566,15 @@ static void v4l_print_create_buffers(const void *arg, bool write_only)
> >>>> v4l_print_format(&p->format, write_only);
> >>>> }
> >>>>
> >>>> +static void v4l_print_ext_create_buffers(const void *arg, bool write_only)
> >>>> +{
> >>>> + const struct v4l2_ext_create_buffers *p = arg;
> >>>> +
> >>>> + pr_cont("index=%d, count=%d, memory=%s, ", p->index, p->count,
> >>>> + prt_names(p->memory, v4l2_memory_names));
> >>>> + v4l_print_ext_pix_format(&p->format, write_only);
> >>>
> >>> Should we also print capabilities and flags?
> >>
> >> I just saw these prints are called after the ioctl handler, and not before,
> >> to I guess it make sense.
> >>
> >> It is not printed by v4l_print_create_buffers(), I think we can add in both then.
> >>
> >>>
> >>>> +}
> >>>> +
> >>>> static void v4l_print_streamparm(const void *arg, bool write_only)
> >>>> {
> >>>> const struct v4l2_streamparm *p = arg;
> >>>> @@ -1220,6 +1249,143 @@ int v4l2_format_to_ext_pix_format(const struct v4l2_format *f,
> >>>> }
> >>>> EXPORT_SYMBOL_GPL(v4l2_format_to_ext_pix_format);
> >>>>
> >>>> +/*
> >>>> + * If mplane_cap is true, b->m.planes should have a valid pointer of a
> >>>> + * struct v4l2_plane array, and b->length with its size
> >>>> + */
> >>>> +int v4l2_ext_buffer_to_buffer(const struct v4l2_ext_buffer *e,
> >>>> + struct v4l2_buffer *b, bool mplane_cap)
> >>>> +{
> >>>> + unsigned int planes_array_size = b->length;
> >>>> + struct v4l2_plane *planes = b->m.planes;
> >>>> + u64 nsecs;
> >>>> +
> >>>> + if (!mplane_cap && e->planes[1].buffer_length != 0)
> >>>> + return -EINVAL;
> >>>> +
> >>>> + memset(b, 0, sizeof(*b));
> >>>> +
> >>>> + b->index = e->index;
> >>>> + b->flags = e->flags;
> >>>> + b->field = e->field;
> >>>> + b->sequence = e->sequence;
> >>>> + b->memory = e->planes[0].memory;
> >>>> + b->request_fd = e->request_fd;
> >>>> + b->timestamp.tv_sec = div64_u64_rem(e->timestamp, NSEC_PER_SEC, &nsecs);
> >>>> + b->timestamp.tv_usec = (u32)nsecs / NSEC_PER_USEC;
> >>>> +
> >>>> + if (mplane_cap) {
> >>>> + unsigned int i;
> >>>> +
> >>>> + if (!planes || !planes_array_size)
> >>>> + return -EINVAL;
> >>>> +
> >>>> + b->m.planes = planes;
> >>>
> >>> planes was initialized to b->m.planes at declaration time. Should we
> >>> perhaps move its declaration to within this block to make it more clear and
> >>> remove this assignment?
> >>
> >> The variable "planes" is saving the pointer of b->m.planes before we do
> >> memset(b, 0, sizeof(*b)), so I can reassing it back if it make sense.
> >>
> >> I can add a comment to make this more clear.
> >>
> >
> > Right, I think the code is a bit confusing. Should we just pass the
> > planes array pointer as a separate argument to the function?
>
> Make sense, this would make sense more clear. I'll update for next version.
>
> >
> >>>
> >>>> +
> >>>> + if (e->type == V4L2_BUF_TYPE_VIDEO_CAPTURE)
> >>>> + b->type = V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE;
> >>>> + else
> >>>> + b->type = V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE;
> >>>> +
> >>>> + for (i = 0; i < VIDEO_MAX_PLANES && i < planes_array_size &&
> >>>> + e->planes[i].buffer_length; i++) {
> >>>> +
> >>>> + if (e->planes[0].memory != e->planes[i].memory)
> >>>> + return -EINVAL;
> >>>> +
> >>>> + if (e->planes[i].offset)
> >>>> + return -EINVAL;
> >>>
> >>> Is it really invalid to have a non-zero offset? Shouldn't the data_offset
> >>> field of the legacy struct be populated instead, in the cases where it was
> >>> defined to be valid?
> >>
> >> My understanding of data_offset, is that it is used when the hardware can
> >> write/read a header to/from the buffer.
> >>
> >> But this doesn't seem to be used by any driver
> >
> > This is not true:
> > https://elixir.bootlin.com/linux/latest/source/drivers/media/platform/qcom/venus/venc.c#L963
>
> Thanks for this pointer.
>
> >
> >> , so there is an attempt to
> >> repourpose it here:
> >>
> >> https://patchwork.linuxtv.org/project/linux-media/patch/1429040689-23808-2-git-send-email-laurent.pinchart@ideasonboard.com/
> >>
> >> But this wans't merged.
> >>
> >> So in the current API, there is no way to specify an offset in the buffer.
> >>
> >> I guess we can repurpose data_offset first, what do you think?
> >>
> >
> > We need to stick to the original behavior for data_offset, so that an
> > encoder has a way to tell the userspace how many bytes of the header
> > it needs to skip.
>
> Right, I'll update this for next version.
>
> >
> >>>
> >>>> +
> >>>> + memset(&b->m.planes[i], 0, sizeof(b->m.planes[i]));
> >>>> +
> >>>> + if (b->memory == V4L2_MEMORY_MMAP)
> >>>> + b->m.planes[i].m.mem_offset = e->planes[i].m.mem_offset;
> >>>> + else if (b->memory == V4L2_MEMORY_DMABUF)
> >>>> + b->m.planes[i].m.fd = e->planes[i].m.dmabuf_fd;
> >>>> + else
> >>>> + b->m.planes[i].m.userptr = e->planes[i].m.userptr;
> >>>> +
> >>>> + b->m.planes[i].bytesused = e->planes[i].plane_length;
> >>>
> >>> I might be getting the meaning of plane_length wrong, but doesn't this
> >>> depend on the direction? If the userspace gives a CAPTURE buffer, it would
> >>> have bytesused = 0, but if the kernel returns it, it would have bytesused =
> >>> <size of the payload>.
> >>
> >> You are right, it depends on the direction, thanks for catching this.
> >>
> >> Also, in the Ext api, we don't have the <size of the payload>, so I'm using the
> >> plane_length instead, I'm not sure if there is a better way.
> >
> > I thought about this for a while and it sounds like in the code added
> > by this series, plane_length is basically used as the old bytesused
> > and buffer_length as the old length. Would it make sense to just
> > preserve the old naming?
>
> Make sense, I thought we could use the length of the plane to other validations,
> but we don't need it. I'll preserve bytesused instead.
>
> >
> >>
> >>>
> >>>> + b->m.planes[i].length = e->planes[i].buffer_length;
> >>>> + }
> >>>> + /* In multi-planar, length contain the number of planes */
> >>>> + b->length = i;
> >>>> + } else {
> >>>> + b->type = e->type;
> >>>> + b->bytesused = e->planes[0].plane_length;
> >>>> + b->length = e->planes[0].buffer_length;
> >>>> +
> >>>> + if (e->planes[0].offset)
> >>>> + return -EINVAL;
> >>>
> >>> Ditto.
> >>
> >> Ack.
> >>
> >>>
> >>>> +
> >>>> + if (b->memory == V4L2_MEMORY_MMAP)
> >>>> + b->m.offset = e->planes[0].m.mem_offset;
> >>>> + else if (b->memory == V4L2_MEMORY_DMABUF)
> >>>> + b->m.fd = e->planes[0].m.dmabuf_fd;
> >>>> + else
> >>>> + b->m.userptr = e->planes[0].m.userptr;
> >>>> + }
> >>>> +
> >>>> + return 0;
> >>>> +}
> >>>> +EXPORT_SYMBOL_GPL(v4l2_ext_buffer_to_buffer);
> >>>> +
> >>>> +int v4l2_buffer_to_ext_buffer(const struct v4l2_buffer *b,
> >>>> + struct v4l2_ext_buffer *e)
> >>>> +{
> >>>> + memset(e, 0, sizeof(*e));
> >>>> +
> >>>> + e->index = b->index;
> >>>> + e->flags = b->flags;
> >>>> + e->field = b->field;
> >>>> + e->sequence = b->sequence;
> >>>> + e->request_fd = b->request_fd;
> >>>> + e->timestamp = b->timestamp.tv_sec * NSEC_PER_SEC +
> >>>> + b->timestamp.tv_usec * NSEC_PER_USEC;
> >>>> + if (V4L2_TYPE_IS_MULTIPLANAR(b->type)) {
> >>>> + unsigned int i;
> >>>> +
> >>>> + if (!b->m.planes)
> >>>> + return -EINVAL;
> >>>> +
> >>>> + if (b->type == V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE)
> >>>> + e->type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
> >>>> + else
> >>>> + e->type = V4L2_BUF_TYPE_VIDEO_OUTPUT;
> >>>> +
> >>>> + /* In multi-planar, length contain the number of planes */
> >>>> + for (i = 0; i < b->length; i++) {
> >>>
> >>> The design of the new struct implies that the planes describe color planes
> >>> and not memory planes, so this code is incorrect, because for non-M format
> >>> variants it would fill in only the first plane of the new struct.
> >>
> >> Yes, as discussed in 1/7, the handling of planes is wrong, I'll correct
> >> this for next version.
> >>
> >>>
> >>>> + if (b->memory == V4L2_MEMORY_MMAP)
> >>>> + e->planes[i].m.mem_offset = b->m.planes[i].m.mem_offset;
> >>>> + else if (b->memory == V4L2_MEMORY_DMABUF)
> >>>> + e->planes[i].m.dmabuf_fd = b->m.planes[i].m.fd;
> >>>> + else
> >>>> + e->planes[i].m.userptr = b->m.planes[i].m.userptr;
> >>>> +
> >>>> + e->planes[i].memory = b->memory;
> >>>> + e->planes[i].buffer_length = b->m.planes[i].length;
> >>>> + e->planes[i].plane_length = b->m.planes[i].bytesused;
> >>>> + if (b->m.planes[i].data_offset)
> >>>> + pr_warn("Ignoring data_offset value %d\n",
> >>>> + b->m.planes[i].data_offset);
> >>>
> >>> Why? As per my comment above, there are valid use cases defined in the spec.
> >>
> >> Please see my comment about about data_offset.
> >>
> >>>
> >>>> + }
> >>>> + } else {
> >>>> + e->type = b->type;
> >>>> + e->planes[0].memory = b->memory;
> >>>> + e->planes[0].plane_length = b->bytesused;
> >>>> + e->planes[0].buffer_length = b->length;
> >>>> + if (b->memory == V4L2_MEMORY_MMAP)
> >>>> + e->planes[0].m.mem_offset = b->m.offset;
> >>>> + else if (b->memory == V4L2_MEMORY_DMABUF)
> >>>> + e->planes[0].m.dmabuf_fd = b->m.fd;
> >>>> + else
> >>>> + e->planes[0].m.userptr = b->m.userptr;
> >>>
> >>> Similar to the MULTIPLANAR case, we should fill in the planes[] entries
> >>> corresponding to the number of color planes of the format, e.g. 2 for NV12.
> >>
> >> Ack.
> >>
> >>>
> >>>> + }
> >>>> +
> >>>> + return 0;
> >>>> +}
> >>>> +EXPORT_SYMBOL_GPL(v4l2_buffer_to_ext_buffer);
> >>>> +
> >>>> static int v4l_querycap(const struct v4l2_ioctl_ops *ops,
> >>>> struct file *file, void *fh, void *arg)
> >>>> {
> >>>> @@ -2473,31 +2639,112 @@ static int v4l_reqbufs(const struct v4l2_ioctl_ops *ops,
> >>>> return ops->vidioc_reqbufs(file, fh, p);
> >>>> }
> >>>>
> >>>> +static int v4l_do_buf_op(int (*op)(struct file *, void *,
> >>>> + struct v4l2_buffer *),
> >>>> + int (*ext_op)(struct file *, void *,
> >>>> + struct v4l2_ext_buffer *),
> >>>> + struct file *file, void *fh, struct v4l2_buffer *b)
> >>>> +{
> >>>> + struct v4l2_ext_buffer e;
> >>>> + int ret;
> >>>> +
> >>>> + ret = check_fmt(file, b->type);
> >>>> + if (ret)
> >>>> + return ret;
> >>>> +
> >>>> + if (op)
> >>>> + return op(file, fh, b);
> >>>> +
> >>>> + ret = v4l2_buffer_to_ext_buffer(b, &e);
> >>>> + if (ret)
> >>>> + return ret;
> >>>> +
> >>>> + ret = ext_op(file, fh, &e);
> >>>> + if (ret)
> >>>> + return ret;
> >>>> +
> >>>> + v4l2_ext_buffer_to_buffer(&e, b, V4L2_TYPE_IS_MULTIPLANAR(b->type));
> >>>> + return 0;
> >>>> +}
> >>>> +
> >>>> +static int v4l_do_ext_buf_op(int (*op)(struct file *, void *,
> >>>> + struct v4l2_buffer *),
> >>>> + int (*ext_op)(struct file *, void *,
> >>>> + struct v4l2_ext_buffer *),
> >>>> + struct file *file, void *fh,
> >>>> + struct v4l2_ext_buffer *e)
> >>>> +{
> >>>> + struct video_device *vdev = video_devdata(file);
> >>>> + struct v4l2_plane planes[VIDEO_MAX_PLANES];
> >>>> + struct v4l2_buffer b;
> >>>> + bool mplane_cap;
> >>>> + int ret;
> >>>> +
> >>>> + ret = check_fmt(file, e->type);
> >>>> + if (ret)
> >>>> + return ret;
> >>>> +
> >>>> + if (ext_op)
> >>>> + return ext_op(file, fh, e);
> >>>> +
> >>>> + mplane_cap = !!(vdev->device_caps &
> >>>> + (V4L2_CAP_VIDEO_CAPTURE_MPLANE |
> >>>> + V4L2_CAP_VIDEO_OUTPUT_MPLANE |
> >>>> + V4L2_CAP_VIDEO_M2M_MPLANE));
> >>>> + b.m.planes = planes;
> >>>> + b.length = VIDEO_MAX_PLANES;
> >>>> + ret = v4l2_ext_buffer_to_buffer(e, &b, mplane_cap);
> >>>> + if (ret)
> >>>> + return ret;
> >>>> +
> >>>> + ret = op(file, fh, &b);
> >>>> + if (ret)
> >>>> + return ret;
> >>>> +
> >>>> + v4l2_buffer_to_ext_buffer(&b, e);
> >>>> + return 0;
> >>>> +}
> >>>> +
> >>>> static int v4l_querybuf(const struct v4l2_ioctl_ops *ops,
> >>>> - struct file *file, void *fh, void *arg)
> >>>> + struct file *file, void *fh, void *arg)
> >>>> {
> >>>> - struct v4l2_buffer *p = arg;
> >>>> - int ret = check_fmt(file, p->type);
> >>>> + return v4l_do_buf_op(ops->vidioc_querybuf, ops->vidioc_ext_querybuf,
> >>>> + file, fh, arg);
> >>>> +}
> >>>>
> >>>> - return ret ? ret : ops->vidioc_querybuf(file, fh, p);
> >>>> +static int v4l_ext_querybuf(const struct v4l2_ioctl_ops *ops,
> >>>> + struct file *file, void *fh, void *arg)
> >>>> +{
> >>>> + return v4l_do_ext_buf_op(ops->vidioc_querybuf,
> >>>> + ops->vidioc_ext_querybuf, file, fh, arg);
> >>>> }
> >>>>
> >>>> static int v4l_qbuf(const struct v4l2_ioctl_ops *ops,
> >>>> - struct file *file, void *fh, void *arg)
> >>>> + struct file *file, void *fh, void *arg)
> >>>> {
> >>>> - struct v4l2_buffer *p = arg;
> >>>> - int ret = check_fmt(file, p->type);
> >>>> + return v4l_do_buf_op(ops->vidioc_qbuf, ops->vidioc_ext_qbuf,
> >>>> + file, fh, arg);
> >>>> +}
> >>>>
> >>>> - return ret ? ret : ops->vidioc_qbuf(file, fh, p);
> >>>> +static int v4l_ext_qbuf(const struct v4l2_ioctl_ops *ops,
> >>>> + struct file *file, void *fh, void *arg)
> >>>> +{
> >>>> + return v4l_do_ext_buf_op(ops->vidioc_qbuf, ops->vidioc_ext_qbuf,
> >>>> + file, fh, arg);
> >>>> }
> >>>>
> >>>> static int v4l_dqbuf(const struct v4l2_ioctl_ops *ops,
> >>>> - struct file *file, void *fh, void *arg)
> >>>> + struct file *file, void *fh, void *arg)
> >>>> {
> >>>> - struct v4l2_buffer *p = arg;
> >>>> - int ret = check_fmt(file, p->type);
> >>>> + return v4l_do_buf_op(ops->vidioc_dqbuf, ops->vidioc_ext_dqbuf,
> >>>> + file, fh, arg);
> >>>> +}
> >>>>
> >>>> - return ret ? ret : ops->vidioc_dqbuf(file, fh, p);
> >>>> +static int v4l_ext_dqbuf(const struct v4l2_ioctl_ops *ops,
> >>>> + struct file *file, void *fh, void *arg)
> >>>> +{
> >>>> + return v4l_do_ext_buf_op(ops->vidioc_dqbuf, ops->vidioc_ext_dqbuf,
> >>>> + file, fh, arg);
> >>>> }
> >>>>
> >>>> static int v4l_create_bufs(const struct v4l2_ioctl_ops *ops,
> >>>> @@ -2513,7 +2760,27 @@ static int v4l_create_bufs(const struct v4l2_ioctl_ops *ops,
> >>>>
> >>>> v4l_sanitize_format(&create->format);
> >>>>
> >>>> - ret = ops->vidioc_create_bufs(file, fh, create);
> >>>> + if (ops->vidioc_create_bufs) {
> >>>> + ret = ops->vidioc_create_bufs(file, fh, create);
> >>>> + } else {
> >>>> + struct v4l2_ext_create_buffers ecreate = {
> >>>> + .count = create->count,
> >>>> + .memory = create->memory,
> >>>> + };
> >>>> +
> >>>> + ret = v4l2_format_to_ext_pix_format(&create->format,
> >>>> + &ecreate.format, true);
> >>>> + if (ret)
> >>>> + return ret;
> >>>> +
> >>>> + ret = ops->vidioc_ext_create_bufs(file, fh, &ecreate);
> >>>> + if (ret)
> >>>> + return ret;
> >>>> +
> >>>> + create->index = ecreate.index;
> >>>> + create->count = ecreate.count;
> >>>> + create->capabilities = ecreate.capabilities;
> >>>> + }
> >>>>
> >>>> if (create->format.type == V4L2_BUF_TYPE_VIDEO_CAPTURE ||
> >>>> create->format.type == V4L2_BUF_TYPE_VIDEO_OUTPUT)
> >>>> @@ -2522,13 +2789,60 @@ static int v4l_create_bufs(const struct v4l2_ioctl_ops *ops,
> >>>> return ret;
> >>>> }
> >>>>
> >>>> +static int v4l_ext_create_bufs(const struct v4l2_ioctl_ops *ops,
> >>>> + struct file *file, void *fh, void *arg)
> >>>> +{
> >>>> + struct v4l2_ext_create_buffers *ecreate = arg;
> >>>> + struct video_device *vdev = video_devdata(file);
> >>>> + struct v4l2_create_buffers create = {
> >>>> + .count = ecreate->count,
> >>>> + .memory = ecreate->memory,
> >>>> + .flags = ecreate->flags,
> >>>> + };
> >>>> + bool mplane_cap;
> >>>> + int ret;
> >>>> +
> >>>> + ret = check_fmt(file, ecreate->format.type);
> >>>> + if (ret)
> >>>> + return ret;
> >>>> +
> >>>> + if (ops->vidioc_ext_create_bufs)
> >>>> + return ops->vidioc_ext_create_bufs(file, fh, ecreate);
> >>>> +
> >>>> + mplane_cap = !!(vdev->device_caps &
> >>>> + (V4L2_CAP_VIDEO_CAPTURE_MPLANE |
> >>>> + V4L2_CAP_VIDEO_OUTPUT_MPLANE |
> >>>> + V4L2_CAP_VIDEO_M2M_MPLANE));
> >>>> + ret = v4l2_ext_pix_format_to_format(&ecreate->format,
> >>>> + &create.format, mplane_cap, true);
> >>>> + if (ret)
> >>>> + return ret;
> >>>> +
> >>>> + ret = v4l_create_bufs(ops, file, fh, &create);
> >>>> + if (ret)
> >>>> + return ret;
> >>>> +
> >>>> + ecreate->index = create.index;
> >>>> + ecreate->count = create.count;
> >>>> + ecreate->capabilities = create.capabilities;
> >>>> +
> >>>> + return 0;
> >>>> +}
> >>>> +
> >>>> static int v4l_prepare_buf(const struct v4l2_ioctl_ops *ops,
> >>>> - struct file *file, void *fh, void *arg)
> >>>> + struct file *file, void *fh, void *arg)
> >>>> {
> >>>> - struct v4l2_buffer *b = arg;
> >>>> - int ret = check_fmt(file, b->type);
> >>>> + return v4l_do_buf_op(ops->vidioc_prepare_buf,
> >>>> + ops->vidioc_ext_prepare_buf,
> >>>> + file, fh, arg);
> >>>> +}
> >>>>
> >>>> - return ret ? ret : ops->vidioc_prepare_buf(file, fh, b);
> >>>> +static int v4l_ext_prepare_buf(const struct v4l2_ioctl_ops *ops,
> >>>> + struct file *file, void *fh, void *arg)
> >>>> +{
> >>>> + return v4l_do_ext_buf_op(ops->vidioc_prepare_buf,
> >>>> + ops->vidioc_ext_prepare_buf,
> >>>> + file, fh, arg);
> >>>> }
> >>>>
> >>>> static int v4l_g_parm(const struct v4l2_ioctl_ops *ops,
> >>>> @@ -3202,12 +3516,15 @@ static const struct v4l2_ioctl_info v4l2_ioctls[] = {
> >>>> IOCTL_INFO(VIDIOC_S_EXT_PIX_FMT, v4l_s_ext_pix_fmt, v4l_print_ext_pix_format, INFO_FL_PRIO),
> >>>> IOCTL_INFO(VIDIOC_REQBUFS, v4l_reqbufs, v4l_print_requestbuffers, INFO_FL_PRIO | INFO_FL_QUEUE),
> >>>> IOCTL_INFO(VIDIOC_QUERYBUF, v4l_querybuf, v4l_print_buffer, INFO_FL_QUEUE | INFO_FL_CLEAR(v4l2_buffer, length)),
> >>>> + IOCTL_INFO(VIDIOC_EXT_QUERYBUF, v4l_ext_querybuf, v4l_print_ext_buffer, INFO_FL_QUEUE | INFO_FL_CLEAR(v4l2_ext_buffer, planes)),
> >>>> IOCTL_INFO(VIDIOC_G_FBUF, v4l_stub_g_fbuf, v4l_print_framebuffer, 0),
> >>>> IOCTL_INFO(VIDIOC_S_FBUF, v4l_stub_s_fbuf, v4l_print_framebuffer, INFO_FL_PRIO),
> >>>> IOCTL_INFO(VIDIOC_OVERLAY, v4l_overlay, v4l_print_u32, INFO_FL_PRIO),
> >>>> IOCTL_INFO(VIDIOC_QBUF, v4l_qbuf, v4l_print_buffer, INFO_FL_QUEUE),
> >>>> IOCTL_INFO(VIDIOC_EXPBUF, v4l_stub_expbuf, v4l_print_exportbuffer, INFO_FL_QUEUE | INFO_FL_CLEAR(v4l2_exportbuffer, flags)),
> >>>> + IOCTL_INFO(VIDIOC_EXT_QBUF, v4l_ext_qbuf, v4l_print_ext_buffer, INFO_FL_QUEUE),
> >>>
> >>> Looking at the other entries, shouldn't this one be 1 line higher?
> >>
> >> Yes.
> >>
> >>>
> >>> That said, I wonder if it wouldn't look cleaner if we just put all the
> >>> EXT ioctls together at the bottom.
> >>
> >> I can move them and we can see if it is better or not.
> >>
> >>>
> >>>> IOCTL_INFO(VIDIOC_DQBUF, v4l_dqbuf, v4l_print_buffer, INFO_FL_QUEUE),
> >>>> + IOCTL_INFO(VIDIOC_EXT_DQBUF, v4l_ext_dqbuf, v4l_print_ext_buffer, INFO_FL_QUEUE),
> >>>> IOCTL_INFO(VIDIOC_STREAMON, v4l_streamon, v4l_print_buftype, INFO_FL_PRIO | INFO_FL_QUEUE),
> >>>> IOCTL_INFO(VIDIOC_STREAMOFF, v4l_streamoff, v4l_print_buftype, INFO_FL_PRIO | INFO_FL_QUEUE),
> >>>> IOCTL_INFO(VIDIOC_G_PARM, v4l_g_parm, v4l_print_streamparm, INFO_FL_CLEAR(v4l2_streamparm, type)),
> >>>> @@ -3272,7 +3589,9 @@ static const struct v4l2_ioctl_info v4l2_ioctls[] = {
> >>>> IOCTL_INFO(VIDIOC_SUBSCRIBE_EVENT, v4l_subscribe_event, v4l_print_event_subscription, 0),
> >>>> IOCTL_INFO(VIDIOC_UNSUBSCRIBE_EVENT, v4l_unsubscribe_event, v4l_print_event_subscription, 0),
> >>>> IOCTL_INFO(VIDIOC_CREATE_BUFS, v4l_create_bufs, v4l_print_create_buffers, INFO_FL_PRIO | INFO_FL_QUEUE),
> >>>> + IOCTL_INFO(VIDIOC_EXT_CREATE_BUFS, v4l_ext_create_bufs, v4l_print_ext_create_buffers, INFO_FL_PRIO | INFO_FL_QUEUE),
> >>>> IOCTL_INFO(VIDIOC_PREPARE_BUF, v4l_prepare_buf, v4l_print_buffer, INFO_FL_QUEUE),
> >>>> + IOCTL_INFO(VIDIOC_EXT_PREPARE_BUF, v4l_ext_prepare_buf, v4l_print_ext_buffer, INFO_FL_QUEUE),
> >>>> IOCTL_INFO(VIDIOC_ENUM_DV_TIMINGS, v4l_stub_enum_dv_timings, v4l_print_enum_dv_timings, INFO_FL_CLEAR(v4l2_enum_dv_timings, pad)),
> >>>> IOCTL_INFO(VIDIOC_QUERY_DV_TIMINGS, v4l_stub_query_dv_timings, v4l_print_dv_timings, INFO_FL_ALWAYS_COPY),
> >>>> IOCTL_INFO(VIDIOC_DV_TIMINGS_CAP, v4l_stub_dv_timings_cap, v4l_print_dv_timings_cap, INFO_FL_CLEAR(v4l2_dv_timings_cap, pad)),
> >>>> diff --git a/include/media/v4l2-ioctl.h b/include/media/v4l2-ioctl.h
> >>>> index 8bbcb74d8ee31..75996657ad1ba 100644
> >>>> --- a/include/media/v4l2-ioctl.h
> >>>> +++ b/include/media/v4l2-ioctl.h
> >>>> @@ -169,16 +169,26 @@ struct v4l2_fh;
> >>>> * :ref:`VIDIOC_REQBUFS <vidioc_reqbufs>` ioctl
> >>>> * @vidioc_querybuf: pointer to the function that implements
> >>>> * :ref:`VIDIOC_QUERYBUF <vidioc_querybuf>` ioctl
> >>>> + * @vidioc_ext_querybuf: pointer to the function that implements
> >>>> + * :ref:`VIDIOC_EXT_QUERYBUF <vidioc_ext_querybuf>` ioctl
> >>>> * @vidioc_qbuf: pointer to the function that implements
> >>>> * :ref:`VIDIOC_QBUF <vidioc_qbuf>` ioctl
> >>>> + * @vidioc_ext_qbuf: pointer to the function that implements
> >>>> + * :ref:`VIDIOC_EXT_QBUF <vidioc_ext_qbuf>` ioctl
> >>>> * @vidioc_expbuf: pointer to the function that implements
> >>>> * :ref:`VIDIOC_EXPBUF <vidioc_expbuf>` ioctl
> >>>> * @vidioc_dqbuf: pointer to the function that implements
> >>>> * :ref:`VIDIOC_DQBUF <vidioc_qbuf>` ioctl
> >>>> + * @vidioc_ext_dqbuf: pointer to the function that implements
> >>>> + * :ref:`VIDIOC_EXT_DQBUF <vidioc_ext_qbuf>` ioctl
> >>>> * @vidioc_create_bufs: pointer to the function that implements
> >>>> * :ref:`VIDIOC_CREATE_BUFS <vidioc_create_bufs>` ioctl
> >>>> + * @vidioc_ext_create_bufs: pointer to the function that implements
> >>>> + * :ref:`VIDIOC_EXT_CREATE_BUFS <vidioc_ext_create_bufs>` ioctl
> >>>> * @vidioc_prepare_buf: pointer to the function that implements
> >>>> * :ref:`VIDIOC_PREPARE_BUF <vidioc_prepare_buf>` ioctl
> >>>> + * @vidioc_ext_prepare_buf: pointer to the function that implements
> >>>> + * :ref:`VIDIOC_EXT_PREPARE_BUF <vidioc_ext_prepare_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
> >>>> @@ -439,17 +449,27 @@ struct v4l2_ioctl_ops {
> >>>> struct v4l2_requestbuffers *b);
> >>>> int (*vidioc_querybuf)(struct file *file, void *fh,
> >>>> struct v4l2_buffer *b);
> >>>> + int (*vidioc_ext_querybuf)(struct file *file, void *fh,
> >>>> + struct v4l2_ext_buffer *b);
> >>>> int (*vidioc_qbuf)(struct file *file, void *fh,
> >>>> struct v4l2_buffer *b);
> >>>> + int (*vidioc_ext_qbuf)(struct file *file, void *fh,
> >>>> + struct v4l2_ext_buffer *b);
> >>>> int (*vidioc_expbuf)(struct file *file, void *fh,
> >>>> struct v4l2_exportbuffer *e);
> >>>> int (*vidioc_dqbuf)(struct file *file, void *fh,
> >>>> struct v4l2_buffer *b);
> >>>> + int (*vidioc_ext_dqbuf)(struct file *file, void *fh,
> >>>> + struct v4l2_ext_buffer *b);
> >>>>
> >>>> int (*vidioc_create_bufs)(struct file *file, void *fh,
> >>>> struct v4l2_create_buffers *b);
> >>>> + int (*vidioc_ext_create_bufs)(struct file *file, void *fh,
> >>>> + struct v4l2_ext_create_buffers *b);
> >>>> int (*vidioc_prepare_buf)(struct file *file, void *fh,
> >>>> struct v4l2_buffer *b);
> >>>> + int (*vidioc_ext_prepare_buf)(struct file *file, void *fh,
> >>>> + struct v4l2_ext_buffer *b);
> >>>>
> >>>> int (*vidioc_overlay)(struct file *file, void *fh, unsigned int i);
> >>>> int (*vidioc_g_fbuf)(struct file *file, void *fh,
> >>>> @@ -758,6 +778,12 @@ int v4l2_ext_pix_format_to_format(const struct v4l2_ext_pix_format *e,
> >>>> struct v4l2_format *f,
> >>>> bool mplane_cap, bool strict);
> >>>>
> >>>> +int v4l2_ext_buffer_to_buffer(const struct v4l2_ext_buffer *e,
> >>>> + struct v4l2_buffer *b,
> >>>> + bool mplane_cap);
> >>>> +int v4l2_buffer_to_ext_buffer(const struct v4l2_buffer *b,
> >>>> + struct v4l2_ext_buffer *e);
> >>>> +
> >>>> /*
> >>>> * The user space interpretation of the 'v4l2_event' differs
> >>>> * based on the 'time_t' definition on 32-bit architectures, so
> >>>> diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
> >>>> index 7123c6a4d9569..334cafdd2be97 100644
> >>>> --- a/include/uapi/linux/videodev2.h
> >>>> +++ b/include/uapi/linux/videodev2.h
> >>>> @@ -996,6 +996,41 @@ struct v4l2_plane {
> >>>> __u32 reserved[11];
> >>>> };
> >>>>
> >>>> +/**
> >>>> + * struct v4l2_ext_plane - extended plane buffer info
> >>>> + * @buffer_length: size of the entire buffer in bytes, should fit
> >>>> + * @offset + @plane_length
> >>>
> >>> Do we actually need this buffer_length at all? We have 3 memory types:
> >>>
> >>> 1) MMAP - here vb2 already knows the buffer size, because it created it.
> >>>
> >>> 2) DMABUF - the DMA-buf kAPI provides the information about buffer size.
> >>>
> >>> 3) USERPTR - this might actually benefit from buffer_length, because there
> >>> are additional alignmnent requirements for the user memory, e.g. the
> >>> offset and size must be cacheline aligned.
> >>>
> >>> Arguably, 1) and 2) are the main usage scenarios, while the user space that
> >>> uses them would have to suffer from added complexity, because of the
> >>> legacy/niche case 3).
> >>>
> >>> Could we make this field valid only for USERPTR?
> >>
> >> I think so, make sense, I'll implement this for next version.
> >>
> >>>
> >>>> + * @plane_length: size of the plane in bytes.
> >>>> + * @mem_offset: If V4L2_MEMORY_MMAP is used, then it can be a "cookie"
> >>>> + * that should be passed to mmap() called on the video node.
> >>>> + * @userptr: when memory is V4L2_MEMORY_USERPTR, a userspace pointer pointing
> >>>> + * to this plane.
> >>>> + * @dmabuf_fd: when memory is V4L2_MEMORY_DMABUF, a userspace file descriptor
> >>>> + * associated with this plane.
> >>>> + * @offset: offset in the memory buffer where the plane starts.
> >>>> + * @memory: enum v4l2_memory; the method, in which the actual video
> >>>> + * data is passed
> >>>> + * @reserved: extra space reserved for future fields, must be set to 0.
> >>>> + *
> >>>> + *
> >>>> + * Buffers consist of one or more planes, e.g. an YCbCr buffer with two planes
> >>>> + * can have one plane for Y, and another for interleaved CbCr components.
> >>>> + * Each plane can reside in a separate memory buffer, or even in
> >>>> + * a completely separate memory node (e.g. in embedded devices).
> >>>> + */
> >>>> +struct v4l2_ext_plane {
> >>>> + __u32 buffer_length;
> >>>> + __u32 plane_length;
> >>>> + union {
> >>>> + __u32 mem_offset;
> >>>> + __u64 userptr;
> >>>> + __s32 dmabuf_fd;
> >>>> + } m;
> >>>> + __u32 offset;
> >>>> + __u32 memory;
> >>>> + __u32 reserved[4];
> >>>> +};
> >>>
> >>> Don't we also need bytesused? Or would plane_length essentially mean the
> >>> amount of space or payload, depending on the usage context?
> >>
> >> In my understanding, plane_length is the max amount of data the plane can
> >> occupy, othersize it can overflow the buffer or mess with another plane
> >> that is in the same buffer on a different offset.
> >>
> >> I'm probably wrong, but I don't really see why the payload size is usefull,
> >> unless if we set a plane_legth that is much bigger then the data it can carry,
> >> that can impact performance.
> >> Payload can also be calculated from the format.
> >
> > It is required for non-2D-image formats, such as compressed bitstream.
> > In that case, the size of the image varies between frames and is
> > usually less than the size of the buffer.
>
> right, ok.
>
> >
> >>
> >> I can add it back if it is usefull. Please let me know your thoughts.
> >>
> >
> > As I mentioned above, it looks like plane_length is used almost
> > exactly the same way bytesused was in the original code, so maybe it
> > could just stay this way?
>
> Ack.
>
> >
> >>>
> >>> Similarly, the original data_offset was useful as a return field, which
> >>> some drivers use to indicate that the beginning of the plane is occupied by
> >>> some header or otherwise irrelevant data, which must be skipped. Would the
> >>> offset field be used for this purpose now?
> >>
> >> I didn't add an equivalent of the data_offset, since it seemed to be
> >> unused (please see my comments about this above).
> >>
> >>>
> >>>> +
> >>>> /**
> >>>> * struct v4l2_buffer - video buffer info
> >>>> * @index: id number of the buffer
> >>>> @@ -1057,6 +1092,33 @@ struct v4l2_buffer {
> >>>> };
> >>>> };
> >>>>
> >>>> +/**
> >>>> + * struct v4l2_ext_buffer - extended video buffer info
> >>>> + * @index: id number of the buffer
> >>>> + * @type: V4L2_BUF_TYPE_VIDEO_CAPTURE or V4L2_BUF_TYPE_VIDEO_OUTPUT
> >>>> + * @flags: buffer informational flags
> >>>
> >>> nit: The order of comments doesn't match the order of fields in the struct.
> >>
> >> Ack.
> >>
> >>>
> >>>> + * @field: enum v4l2_field; field order of the image in the buffer
> >>>> + * @timestamp: frame timestamp
> >>>> + * @sequence: sequence count of this frame
> >>>> + * @planes: per-plane buffer information
> >>>> + * @request_fd: fd of the request that this buffer should use
> >>>> + * @reserved: extra space reserved for future fields, must be set to 0
> >>>> + *
> >>>> + * Contains data exchanged by application and driver using one of the Streaming
> >>>> + * I/O methods.
> >>>> + */
> >>>> +struct v4l2_ext_buffer {
> >>>> + __u32 index;
> >>>> + __u32 type;
> >>>> + __u32 field;
> >>>> + __u32 sequence;
> >>>> + __u64 flags;
> >>>> + __u64 timestamp;
> >>>
> >>> What's the unit? How does this play with the other UAPI that the user space
> >>> may use, e.g. clock_gettime() which returns struct timespec?
> >>
> >> The unity is nsec:
> >>
> >> e->timestamp = b->timestamp.tv_sec * NSEC_PER_SEC +
> >> b->timestamp.tv_usec * NSEC_PER_USEC;
> >>
> >> I can clarify in the docs, is this ok?
> >>
> >
> > Yes, it definitely needs to be documented. That said, what's the
> > rationale for switching from the timeval representation to the flat
> > nsec-based one?
>
> According to https://patchwork.kernel.org/project/linux-media/patch/20190319145243.25047-4-boris.brezillon@collabora.com/
> This avoids y2038 issue.
Fair enough, thanks.
Best regards,
Tomasz
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