Re: [PATCH v4 0/3] IR decoding using BPF

[Sean Young <sean@mess.org>]

On Wed, May 23, 2018 at 02:21:27PM +0200, Daniel Borkmann wrote:
> 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/?

There are no merge conflict and as of yet, I'm not expecting any. If anything
I suspect the bpf tree is more likely to change, so merging via bpf-next
might make more sense.

Thanks

Sean

> 
> 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 <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
> >