On 05/18/2018 04:07 PM, Sean Young wrote:

The kernel IR decoders (drivers/media/rc/ir-*-decoder.c) support the most
widely used IR protocols, but there are many protocols which are not
supported[1]. For example, the lirc-remotes[2] repo has over 2700 remotes,
many of which are not supported by rc-core. There is a "long tail" of
unsupported IR protocols, for which lircd is need to decode the IR .

IR encoding is done in such a way that some simple circuit can decode it;
therefore, bpf is ideal.

In order to support all these protocols, here we have bpf based IR decoding.
The idea is that user-space can define a decoder in bpf, attach it to
the rc device through the lirc chardev.

Separate work is underway to extend ir-keytable to have an extensive library
of bpf-based decoders, and a much expanded library of rc keymaps.

Another future application would be to compile IRP[3] to a IR BPF program, and
so support virtually every remote without having to write a decoder for each.
It might also be possible to support non-button devices such as analog
directional pads or air conditioning remote controls and decode the target
temperature in bpf, and pass that to an input device.

Mauro, are you fine with this series going via bpf-next? How ugly would this
get with regards to merge conflicts wrt drivers/media/rc/?

Thanks,
Daniel

Thanks,

Sean Young

[1] http://www.hifi-remote.com/wiki/index.php?title=DecodeIR
[2] https://sourceforge.net/p/lirc-remotes/code/ci/master/tree/remotes/
[3] http://www.hifi-remote.com/wiki/index.php?title=IRP_Notation

Changes since v3:
 - Implemented review comments from Quentin Monnet and Y Song (thanks!)
 - More helpful and better formatted bpf helper documentation
 - Changed back to bpf_prog_array rather than open-coded implementation
 - scancodes can be 64 bit
 - bpf gets passed values in microseconds, not nanoseconds.
   microseconds is more than than enough (IR receivers support carriers upto
   70kHz, at which point a single period is already 14 microseconds). Also,
   this makes it much more consistent with lirc mode2.
 - Since it looks much more like lirc mode2, rename the program type to
   BPF_PROG_TYPE_LIRC_MODE2.
 - Rebased on bpf-next

Changes since v2:
 - Fixed locking issues
 - Improved self-test to cover more cases
 - Rebased on bpf-next again

Changes since v1:
 - Code review comments from Y Song [off-list ref] and
   Randy Dunlap [off-list ref]
 - Re-wrote sample bpf to be selftest
 - Renamed RAWIR_DECODER -> RAWIR_EVENT (Kconfig, context, bpf prog type)
 - Rebase on bpf-next
 - Introduced bpf_rawir_event context structure with simpler access checking

Sean Young (3):
  bpf: bpf_prog_array_copy() should return -ENOENT if exclude_prog not
    found
  media: rc: introduce BPF_PROG_LIRC_MODE2
  bpf: add selftest for lirc_mode2 type program

 drivers/media/rc/Kconfig                      |  13 +
 drivers/media/rc/Makefile                     |   1 +
 drivers/media/rc/bpf-lirc.c                   | 308 ++++++++++++++++++
 drivers/media/rc/lirc_dev.c                   |  30 ++
 drivers/media/rc/rc-core-priv.h               |  22 ++
 drivers/media/rc/rc-ir-raw.c                  |  12 +-
 include/linux/bpf_rcdev.h                     |  30 ++
 include/linux/bpf_types.h                     |   3 +
 include/uapi/linux/bpf.h                      |  53 ++-
 kernel/bpf/core.c                             |  11 +-
 kernel/bpf/syscall.c                          |   7 +
 kernel/trace/bpf_trace.c                      |   2 +
 tools/bpf/bpftool/prog.c                      |   1 +
 tools/include/uapi/linux/bpf.h                |  53 ++-
 tools/include/uapi/linux/lirc.h               | 217 ++++++++++++
 tools/lib/bpf/libbpf.c                        |   1 +
 tools/testing/selftests/bpf/Makefile          |   8 +-
 tools/testing/selftests/bpf/bpf_helpers.h     |   6 +
 .../testing/selftests/bpf/test_lirc_mode2.sh  |  28 ++
 .../selftests/bpf/test_lirc_mode2_kern.c      |  23 ++
 .../selftests/bpf/test_lirc_mode2_user.c      | 154 +++++++++
 21 files changed, 974 insertions(+), 9 deletions(-)
 create mode 100644 drivers/media/rc/bpf-lirc.c
 create mode 100644 include/linux/bpf_rcdev.h
 create mode 100644 tools/include/uapi/linux/lirc.h
 create mode 100755 tools/testing/selftests/bpf/test_lirc_mode2.sh
 create mode 100644 tools/testing/selftests/bpf/test_lirc_mode2_kern.c
 create mode 100644 tools/testing/selftests/bpf/test_lirc_mode2_user.c