On 7/20/20 8:57 AM, Tomasz Figa wrote: > Hi Helen, > > On Fri, Jul 17, 2020 at 1:55 PM Helen Koike <helen.koike@xxxxxxxxxxxxx> wrote: >> >> Hi, >> >> I'm sorry for taking too long to submit v4. >> >> It is not perfect, not all v4l2-compliance tests passes, but I'd like a review, >> specially on the API and potential problems, so I can focus on improving implementation >> and maybe drop the RFC tag for next version. >> >> Follow below what changed in v4 and some items I'd like to discuss: >> >> >> * Ioctl to replace v4l2_pix_format >> --------------------------------------------------------------------------------- >> During last media summit, we agreed to create ioctls that replace the v4l2_pix_format >> struct and leave the other structs in the v4l2_format union alone. >> Thus I refactored the code to receive struct v4l2_ext_pix_format, and I renamed the >> ioctls, so now we have: >> >> int ioctl(int fd, VIDIOC_G_EXT_FMT, struct v4l2_ext_pix_format *argp); >> int ioctl(int fd, VIDIOC_S_EXT_FMT, struct v4l2_ext_pix_format *argp); >> int ioctl(int fd, VIDIOC_TRY_EXT_FMT, struct v4l2_ext_pix_format *argp); >> >> The only valid types are V4L2_BUF_TYPE_VIDEO_CAPTURE and V4L2_BUF_TYPE_VIDEO_OUTPUT, >> all the other types are invalid with this API. >> >> >> * Modifiers >> --------------------------------------------------------------------------------- >> I understand that unifying DRM and V4L2 pixel formats is not possible, but I'd like >> to unify the modifiers [1]. >> >> [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/include/uapi/drm/drm_fourcc.h#n290 >> >> Should we use the DRM modifiers directly in the V4L2 API? >> Or should we move this header to a common place and change the prefix? (which requires >> us to sync with DRM community). >> Or should we create a v4l2 header, defining V4L2_ prefixed macros mapping to DRM_ >> macros? >> >> For now, patch 1/6 includes drm/drm_fourcc.h and it is using DRM_FORMAT_MOD_* >> >> As discussed before, It would be nice to have documentation describing DRM fourcc >> equivalents (I'm not sure if someone started this already), listing the number of >> planes per format. >> >> We should also document which pixelformats are valid for the EXT_API, since multiplanar >> and tile versions like V4L2_PIX_FMT_NV12MT_16X16 (which seems equivalent to >> DRM_FORMAT_MOD_SAMSUNG_16_16_TILE, and could have a more generic name) should be >> replaced by a modifier. >> >> Regarding flags [2] field in struct v4l2_pix_format_mplane [3]: >> The only defined flag is V4L2_PIX_FMT_FLAG_PREMUL_ALPHA, and it is only used by vsp1 driver. >> Which I believe could be replaced by a modifier, to avoid another field that changes >> pixel formats, so I removed it from the EXT API (we can always add it back later with >> the reserved fields). >> >> [2] https://linuxtv.org/downloads/v4l-dvb-apis-new/userspace-api/v4l/pixfmt-reserved.html#format-flags >> [3] https://linuxtv.org/downloads/v4l-dvb-apis-new/userspace-api/v4l/pixfmt-v4l2-mplane.html?highlight=v4l2_pix_format_mplane#c.v4l2_pix_format_mplane >> >> We also discussed to add a new ENUM_FMT_EXT ioctl to return all pixelformats + modifiers >> combinations. I still didn't add it in this version, but I don't think it affects >> what is in this RFC and it can be added later. >> >> >> * Buffers/Plane offset >> --------------------------------------------------------------------------------- >> >> My understanding is that inside a memory buffer we can have multiple planes in random >> offsets. >> I was comparing with the DRM API [4], where it can have the same dmabuf for multiple >> planes in different offsets, and I started to think we could simplify our API, so >> I took the liberty to do some more changes, please review struct v4l2_ext_plane in >> this RFC. >> >> I removed the data_offset, since it is unused (See Laurent's RFC repurposing this >> field [5]). And comparing to the DRM API, it seems to me we only need a single offset >> field. >> >> We could also check about overlapping planes in a memory buffer, but this is complicated >> if we use the same memory buffer with different v4l2_ext_buffer objects. We can also leave >> to the driver to check situations that may cause HW errors. >> >> [4] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/include/uapi/drm/drm_mode.h#n489 >> [5] https://patchwork.linuxtv.org/patch/29177/ >> >> >> * Multistream Channels >> --------------------------------------------------------------------------------- >> During last media summit, we discussed about adding a channel number to the API to >> support multistreams. i.e, to have multiple queues through a single video node. >> >> Use cases: >> >> - Blitters: can take multiple streams as input, which would require multiple OUTPUT queues. >> >> As Nicolas was explaining me: >> "The blitters comes with a lot of variation between hardware. Most blitters at >> least support 3 frames buffer. 2 inputs and one output. The second input is usually >> optional, as the output buffer data is not always overwritten (e.g. SRC_OVER >> blend or 1 input). Some of them have additional solid color or pattern that can >> be used too. Advanced blitters will have composition feature, and may support more >> input buffers to reduce the added latency that would be normally done through cascading >> the operations. Note that each input can have different size and different cropping >> region. Many blitters can scale and render to a sub-region of the CAPTURE buffer." >> >> - Multis-calers: can produce multiple streams, which would require multiple CAPTURE queues. >> >> As Nicolas was explaining me: >> "This type of HW (or soft IP) is commonly found on HW used to produce internet >> streams for fragmented and scalable protocols (HLS, DASH). Basically they are >> used to transform one stream into multiple sized streams prior from being encoded." >> >> Modeling as channels allows the API to have synchronized Start/Stop between queues, >> and also avoid the complexity of using the Media API in a topology with multiple video >> nodes, which complicates userspace. >> >> This requires adding a new channel id in ioctls for formats (G_FMT/S_FMT/TRY_FMT), and >> also for buffers (QBUF/DBUF). >> We also need a mechanism to enumerate channels and their properties. >> Since we don't have a clear view how this would work, for now I'm leaving reserved bits >> in the structs, so we can add them later. >> >> >> * Timecode >> --------------------------------------------------------------------------------- >> During last media summit, we discussed to return the v4l2_timecode field to the API, >> since Nicolas mentioned that, even if it is not used by any upstreamed driver, it >> is used by out-of-tree drivers. >> >> I've been discussing with Nicolas about this, and we can avoid adding too many metadata >> to the buffer struct by using the Read-Only Request API [6] for retrieving more information >> when required, similar to HDR. >> >> The RO Request API has the ability to read a control using a request that has already >> completed, the control value lives as long as the request object. If it's not read >> (or if there was no request), the data is simply ignored/discard. >> >> Since no upstream driver uses the timecode field, there are no conversions that need >> to be done. >> >> [6] https://patchwork.kernel.org/cover/11635927/ >> >> >> * Other changes (and some questions) in this version: >> --------------------------------------------------------------------------------- >> - Added reserved fields to struct >> >> - The only difference between previously proposed VIDIOC_EXT_EXPBUF and VIDIOC_EXPBUF, >> was that with VIDIOC_EXT_EXPBUF we can export multiple planes at once. I think we >> can add this later, so I removed it from this RFC to simplify it. >> >> - v4l2_buffer [7] has a memory field (enum v4l2_memory [8]). We kept this field in >> struct v4l2_ext_buffer, buf I was wondering if this shouldn't be in struct v4l2_ext_plane >> instead. >> >> [7] https://linuxtv.org/downloads/v4l-dvb-apis-new/userspace-api/v4l/buffer.html?highlight=v4l2_buffer#c.v4l2_buffer >> [8] https://linuxtv.org/downloads/v4l-dvb-apis-new/userspace-api/v4l/buffer.html?highlight=v4l2_memory#c.v4l2_memory >> >> - In struct v4l2_ext_pix_format, we have: >> >> struct v4l2_plane_ext_pix_format plane_fmt[VIDEO_MAX_PLANES]; >> >> The number of planes can be deducted from plane_fmt[i].sizeimage != 0, so I removed >> the num_planes field. Please let me know if we can't use sizeimage for this. >> In DRM, we know the number of planes from drm_mode_fb_cmd2 by the number of handle >> args passed which are not 0. >> This also avoids num_planes to be bigger then VIDEO_MAX_PLANES. >> >> - Added flags field to struct v4l2_ext_create_buffers >> >> >> * Fixed bugs here and there >> --------------------------------------------------------------------------------- >> I fixed some bugs found with v4l2-compliance (not all of them yet), >> through script v4l-utils/contrib/test/test-media. >> >> I adapted what Boris did for v4l-utils in previous version to this version: >> https://gitlab.collabora.com/koike/v4l-utils/-/tree/ext-api/wip >> >> Boris' questions regarding DMABUF in last version still holds [9]. >> >> [9] https://patchwork.linuxtv.org/project/linux-media/cover/20191008091119.7294-1-boris.brezillon@xxxxxxxxxxxxx/ >> >> >> Please, let me know your feedback, >> Helen >> >> >> Boris Brezillon (5): >> media: v4l2: Extend pixel formats to unify single/multi-planar >> handling (and more) >> media: videobuf2: Expose helpers to implement the _ext_fmt and >> _ext_buf hooks >> media: mediabus: Add helpers to convert a ext_pix format to/from a >> mbus_fmt >> media: vivid: Convert the capture and output drivers to >> EXT_FMT/EXT_BUF >> media: vimc: Implement the ext_fmt and ext_buf hooks >> >> Hans Verkuil (1): >> media: v4l2: Add extended buffer operations >> >> .../media/common/videobuf2/videobuf2-core.c | 2 + >> .../media/common/videobuf2/videobuf2-v4l2.c | 549 +++++----- >> .../media/test-drivers/vimc/vimc-capture.c | 61 +- >> drivers/media/test-drivers/vimc/vimc-common.c | 6 +- >> drivers/media/test-drivers/vimc/vimc-common.h | 2 +- >> drivers/media/test-drivers/vivid/vivid-core.c | 70 +- >> .../test-drivers/vivid/vivid-touch-cap.c | 26 +- >> .../test-drivers/vivid/vivid-touch-cap.h | 3 +- >> .../media/test-drivers/vivid/vivid-vid-cap.c | 169 +--- >> .../media/test-drivers/vivid/vivid-vid-cap.h | 15 +- >> .../media/test-drivers/vivid/vivid-vid-out.c | 193 ++-- >> .../media/test-drivers/vivid/vivid-vid-out.h | 15 +- >> drivers/media/v4l2-core/v4l2-dev.c | 50 +- >> drivers/media/v4l2-core/v4l2-ioctl.c | 934 ++++++++++++++++-- >> include/media/v4l2-ioctl.h | 60 ++ >> include/media/v4l2-mediabus.h | 42 + >> include/media/videobuf2-core.h | 6 +- >> include/media/videobuf2-v4l2.h | 21 +- >> include/uapi/linux/videodev2.h | 144 +++ >> 19 files changed, 1650 insertions(+), 718 deletions(-) > > I don't see any documentation being added by this series. I think it's > been a long standing issue with this series and makes it difficult to > review the UAPI itself, in separation from the kernel implementation > details, which is especially important for any non-kernel developers > willing to provide feedback. Agreed, I'll re-spin a new version with docs. Regards, Helen > > Best regards, > Tomasz >
