On Mon, Jul 17, 2017 at 11:20:38AM +0200, Matthias Reichl wrote:
> While testing serial_ir on kernel 4.11.8 with ir-keytable 1.12.3
> I noticed that my /etc/rc_maps.cfg configuration wasn't applied.
> Manually running "ir-keytable -a /etc/rc_maps.cfg -s rc0" always
> worked fine, though.
>
> Digging further into this I tracked it down to the udev rule
> being racy. The udev rule triggers on the rc subsystem, but this
> is before the input and event devices are created.
That's an interesting race condition, I haven't seen this before.
> One solution is to trigger ir-keytable -a execution from the event device
> creation instead. I'm currently testing with the following udev rule:
>
> ACTION=="add", SUBSYSTEMS=="rc", GOTO="begin"
> GOTO="end"
>
> LABEL="begin"
>
> SUBSYSTEM=="rc", ENV{rc_sysdev}="$name"
>
> SUBSYSTEM=="input", IMPORT{parent}="rc_sysdev"
>
> KERNEL=="event[0-9]*", ENV{rc_sysdev}=="?*", \
> RUN+="/usr/bin/ir-keytable -a /etc/rc_maps.cfg -s $env{rc_sysdev}"
>
> LABEL="end"
>
> That udev rule is a bit messy, ir-keytable -a needs the rcX sysdev,
> which doesn't seem to be easily available from the event node in
> the input subsystem, so I'm propagating that info through an
> environment variable.
This is a good idea; this also solves the problem of udev firing off
ir-keytable for transmit-only devices, which have no input device.
> So far testing is working fine, but hints for better/nicer solutions
> are welcome!
So far I've only come up with a minor change:
ACTION!="add", SUBSYSTEMS!="rc", GOTO="rc_dev_end"
SUBSYSTEM=="rc", ENV{rc_sysdev}="$name"
SUBSYSTEM=="input", IMPORT{parent}="rc_sysdev"
KERNEL=="event[0-9]*", ENV{rc_sysdev}=="?*", RUN+="/usr/bin/ir-keytable -a /etc/rc_maps.cfg -s $env{rc_sysdev}"
LABEL="rc_dev_end"
I think we should get this merged into v4l-utils, it solves a real issue.
Sean
