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SubjectRe: [PATCH v4 0/3] IR decoding using BPF
Hi Sean,

On Fri, May 18, 2018 at 03:07:27PM +0100, 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.

Thanks a lot, this looks like a very interesting feature to me!

Unfortunately I don't have time to test it ATM, but please keep
me posted - also on ir-keytable progress - I'm rather excited
to give it a try.

so long & thanks,

Hias

>
> 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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