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From: Kamil Debski <k.debski <at> samsung.com>
Subject: [RFC/PATCH v4 0/4] Multi Format Codec 5.0 driver for S5PC110 SoC
Newsgroups: gmane.linux.drivers.video-input-infrastructure
Date: Thursday 9th December 2010 13:35:19 UTC (over 7 years ago)

Last week v3 of this driver has been posted. Since then the driver was
to use the newest videobuf2 version - v6. Two very long functions have been
split to make the code more readible. Minor changes include tidying the
comments and replacing remaining magic numbers with defines.

I would be grateful for your comments. Original cover letter ant detailed
log has been attached below.

Best regards,
Kamil Debski

* Changelog:

 Changes since v3

1) Update to the v6 videobuf2 API (here thanks go to Marek Szyprowski)
- s5p_mfc_buf_negotiate and s5p_mfc_buf_setup_plane functions
have been merged
- queue initialization has been adapted to the new API
- use of the allocator memops has been changed, now there are single
memops for all the allocator contexts

2) Split of the s5p_mfc_try_run and s5p_mfc_handle_frame_int functions
- parts of the s5p_mfc_try_run function have been moved to separate
functions (s5p_mfc_get_new_ctx, s5p_mfc_run_dec_last_frames,
s5p_mfc_run_dec_frame, s5p_mfc_run_get_inst_no, s5p_mfc_run_return_inst
- s5p_mfc_handle_frame_int has been split to the following functions:
s5p_mfc_handle_frame_all_extracted, s5p_mfc_handle_frame_new
and s5p_mfc_handle_frame to handle different cases

3) Remove remaining magic numbers and tidy up comments

 Changes since v2

1) Update to newest videobuf2 API
This is the major change from v2. The videobuf2 API will hopefully have no
major API changes. Buffer initialization has been moved from buf_prepare
callback to buf_init to simplify the process. Locking mechanism has been
modified to the requirements of new videobuf2 version.
2) Code cleanup
Removed more magic contants and replaced them with appropriate defines.
code to use unlocked_ioctl instead of ioctl in v4l2 file ops.
3) Allocators
All internal buffer allocations are done using the selected vb2 allocator,
instead of using CMA functions directly.

 Changes since v1

1) Cleanup accoridng to Peter Oh suggestions on the mailing list (Thanks).

* Original cover letter:


The purpose of this RFC is to discuss the driver for a hw video codec
embedded in the new Samusng's SoCs. Multi Format Codec 5.0 is able to
handle video decoding of in a range of formats.

So far no hardware codec was supported in V4L2 and this would be the
first one. I guess there are more similar device that would benefit from
a V4L2 unified interface. I suggest a separate control class for codec
devices - V4L2_CTRL_CLASS_CODEC.

Internally the driver uses videobuf2 framework and CMA memory allocator.
I am aware that those have not yet been merged, but I wanted to start
discussion about the driver earlier so it could be merged sooner. The
driver posted here is the initial version, so I suppose it will require
more work.

 Device interface

The driver principle is based on the idea of memory-to-memory devices:
it provides a single video node and each opened file handle gets its own
private context with separate buffer queues. Each context consist of 2
buffer queues: OUTPUT (for source buffers, i.e. encoded video frames)
and CAPTURE (for destination buffers, i.e. decoded raw video frames).
The process of decoding video data from stream is a bit more complicated
than typical memory-to-memory processing, that's why the m2m framework
is not directly used (it is too limited for this case). The main reason
for this is the fact that the CAPTURE buffers can be dequeued in a
different order than they queued. The hw block decides which buffer has
been completely processed. This is due to the structure of most
compressed video streams - use of B frames causes that decoding and
display order may be different.

 Decoding initialization path

First the OUTPUT queue is initialized. With S_FMT the application
chooses which video format to decode and what size should be the input
buffer. Fourcc values have been defined for different codecs e.g.
V4L2_PIX_FMT_H264 for h264. Then the OUTPUT buffers are requested and
mmaped. The stream header frame is loaded into the first buffer, queued
and streaming is enabled. At this point the hardware is able to start
processing the stream header and afterwards it will have information
about the video dimensions and the size of the buffers with raw video

The next step is setting up the CAPTURE queue and buffers. The width,
height, buffer size and minimum number of buffers can be read with G_FMT
call. The application can request more output buffer if necessary. After
requesting and mmaping buffers the device is ready to decode video

The stream frames (ES frames) are written to the OUTPUT buffers, and
decoded video frames can be read from the CAPTURE buffers. When no more
source frames are present a single buffer with bytesused set to 0 should
be queued. This will inform the driver that processing should be
finished and it can dequeue all video frames that are still left. The
number of such frames is dependent on the stream and its internal
structure (how many frames had to be kept as reference frames for
decoding, etc).

 Usage summary

This is a step by step summary of the video decoding (from user
application point of view, with 2 treads and blocking api):

01. S_FMT(OUTPUT, V4L2_PIX_FMT_H264, ...)
03. for i=1..n MMAP(OUTPUT, i)
04. put stream header to buffer #1
05. QBUF(OUTPUT, #1)
09. for j=1..m MMAP(CAPTURE, j)
10. for j=1..m QBUF(CAPTURE, #j)

display thread:
12. DQBUF(CAPTURE) -> got decoded video data in buffer #j
13. display buffer #j
15. goto 12

parser thread:
16. put next ES frame to buffer #i
17. QBUF(OUTPUT, #i)
18. DQBUF(OUTPUT) -> get next empty buffer #i 19. goto 16


Similar usage sequence can be achieved with single threaded application
and non-blocking api with poll() call.

Branch with MFC, CMA and videobuf2 will be soon available at
This tree is based on 2.6.37 rc4.

Please have a look at the code and the idea of how to introduce codec
devices to V4L2. Comments will be very much appreciated.

Patch summary:

Kamil Debski (4):
  Changes in include/linux/videodev2.h for MFC
  MFC: Add MFC 5.1 driver to plat-s5p, mach-s5pv210 and mach-s5pv210
  MFC: Added MFC 5.1 V4L2 driver
  s5pv210: Enable MFC on Goni

 arch/arm/mach-s5pv210/Kconfig                   |    1 +
 arch/arm/mach-s5pv210/clock.c                   |    6 +
 arch/arm/mach-s5pv210/include/mach/map.h        |    4 +
 arch/arm/mach-s5pv210/mach-goni.c               |    1 +
 arch/arm/plat-s5p/Kconfig                       |    5 +
 arch/arm/plat-s5p/Makefile                      |    1 +
 arch/arm/plat-s5p/dev-mfc5.c                    |   37 +
 arch/arm/plat-samsung/include/plat/devs.h       |    2 +
 drivers/media/video/Kconfig                     |    8 +
 drivers/media/video/Makefile                    |    1 +
 drivers/media/video/s5p-mfc/Makefile            |    3 +
 drivers/media/video/s5p-mfc/regs-mfc5.h         |  335 ++++
 drivers/media/video/s5p-mfc/s5p_mfc.c           | 2031
 drivers/media/video/s5p-mfc/s5p_mfc_common.h    |  222 +++
 drivers/media/video/s5p-mfc/s5p_mfc_ctrls.h     |  173 ++
 drivers/media/video/s5p-mfc/s5p_mfc_debug.h     |   47 +
 drivers/media/video/s5p-mfc/s5p_mfc_intr.c      |   92 +
 drivers/media/video/s5p-mfc/s5p_mfc_intr.h      |   26 +
 drivers/media/video/s5p-mfc/s5p_mfc_memory.h    |   43 +
 drivers/media/video/s5p-mfc/s5p_mfc_opr.c       |  870 ++++++++++
 drivers/media/video/s5p-mfc/s5p_mfc_opr.h       |  131 ++
 include/linux/videodev2.h                       |   48 +
 25 files changed, 4136 insertions(+), 1 deletions(-)
 create mode 100644 arch/arm/plat-s5p/dev-mfc5.c
 create mode 100644 drivers/media/video/s5p-mfc/Makefile
 create mode 100644 drivers/media/video/s5p-mfc/regs-mfc5.h
 create mode 100644 drivers/media/video/s5p-mfc/s5p_mfc.c
 create mode 100644 drivers/media/video/s5p-mfc/s5p_mfc_common.h
 create mode 100644 drivers/media/video/s5p-mfc/s5p_mfc_ctrls.h
 create mode 100644 drivers/media/video/s5p-mfc/s5p_mfc_debug.h
 create mode 100644 drivers/media/video/s5p-mfc/s5p_mfc_intr.c
 create mode 100644 drivers/media/video/s5p-mfc/s5p_mfc_intr.h
 create mode 100644 drivers/media/video/s5p-mfc/s5p_mfc_memory.h
 create mode 100644 drivers/media/video/s5p-mfc/s5p_mfc_opr.c
 create mode 100644 drivers/media/video/s5p-mfc/s5p_mfc_opr.h
CD: 3ms