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Subject[PATCH v4 0/3] IR decoding using BPF
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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.

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 <ys114321@gmail.com> and
Randy Dunlap <rdunlap@infradead.org>
- 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

--
2.17.0

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