linux-kernel - [PATCH v3 0/2] IR decoding using BPF

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Message-Id: <cover.1526504511.git.sean@mess.org>
Date:   Wed, 16 May 2018 22:04:39 +0100
From:   Sean Young <sean@...s.org>
To:     linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        Alexei Starovoitov <ast@...nel.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>, netdev@...r.kernel.org,
        Matthias Reichl <hias@...us.com>,
        Devin Heitmueller <dheitmueller@...nellabs.com>,
        Y Song <ys114321@...il.com>
Subject: [PATCH v3 0/2] IR decoding using BPF

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 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@...il.com> and
   Randy Dunlap <rdunlap@...radead.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 (2):
  media: rc: introduce BPF_PROG_RAWIR_EVENT
  bpf: add selftest for rawir_event type program

 drivers/media/rc/Kconfig                      |  13 +
 drivers/media/rc/Makefile                     |   1 +
 drivers/media/rc/bpf-rawir-event.c            | 363 ++++++++++++++++++
 drivers/media/rc/lirc_dev.c                   |  24 ++
 drivers/media/rc/rc-core-priv.h               |  24 ++
 drivers/media/rc/rc-ir-raw.c                  |  14 +-
 include/linux/bpf_rcdev.h                     |  30 ++
 include/linux/bpf_types.h                     |   3 +
 include/uapi/linux/bpf.h                      |  55 ++-
 kernel/bpf/syscall.c                          |   7 +
 tools/bpf/bpftool/prog.c                      |   1 +
 tools/include/uapi/linux/bpf.h                |  57 ++-
 tools/lib/bpf/libbpf.c                        |   1 +
 tools/testing/selftests/bpf/Makefile          |   8 +-
 tools/testing/selftests/bpf/bpf_helpers.h     |   6 +
 tools/testing/selftests/bpf/test_rawir.sh     |  37 ++
 .../selftests/bpf/test_rawir_event_kern.c     |  26 ++
 .../selftests/bpf/test_rawir_event_user.c     | 130 +++++++
 18 files changed, 792 insertions(+), 8 deletions(-)
 create mode 100644 drivers/media/rc/bpf-rawir-event.c
 create mode 100644 include/linux/bpf_rcdev.h
 create mode 100755 tools/testing/selftests/bpf/test_rawir.sh
 create mode 100644 tools/testing/selftests/bpf/test_rawir_event_kern.c
 create mode 100644 tools/testing/selftests/bpf/test_rawir_event_user.c

-- 
2.17.0