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SubjectRe: [PATCH v4 0/3] IR decoding using BPF
Sean, I'd like to echo Matthias's appreciation for your work with this
BPF project. I'm very much looking forward to the possibility of using
my remotes directly with decoders generated from the existing
lircd.conf's. Excited seeing your work progress!

Cheers,
Derek

On Tue, May 22, 2018 at 6:50 AM, Matthias Reichl <hias@horus.com> wrote:
> 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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