[RFC libevdev] Enable event logging for debugging

[David Herrmann]

Hi

On Thu, Apr 3, 2014 at 11:33 PM, Peter Hutterer
<peter.hutterer at who-t.net> wrote:
> I see a couple of issues here: one is that libevdev has _no_ connection to
> systemd at all. it doesn't even use udev and I like to keep it simple that
> way. which is why the minor number is currently required instead of the
> device node. so that makes filtering on the device node hard to begin with
> (we could guess the node with a loop through /dev/input though)

Ugh, you guys misunderstood me. I was in no way implying a relation to
systemd, "journalctl" was just a way to filter messages. I could have
said "tee evdev.log | grep STH" instead. I just thought people are
more familiar with journald-style KEY/VALUE filtering. Anyhow, all I
was saying is that I'm fine with libevdev-internal filtering, as long
as "log everything with a node/dev_t attribute" stays supported. The
important thing here is the proper attribution, though.

> that is exactly the point of this patch. logging every event from every
> device at all times is a large amount of data, especially with touchpads,
> touchscreens or graphics tablets. And in 99% of the use-cases that data is
> just wasting space and isn't used.

Imho, logging is cheap and 1% of useful data is still a reasonable
amount, but I don't mind if others disagree.

> The real use of this is to be able to get sequences for _bugs_ without
> having to tell users to apply a patch from here and then another patch from
> there. Hence the environment variable, it's easy to set, no recompilation is
> needed but the data still goes to the same log as before.

Env-vars are perfect for that! Please go ahead.

Cheers
David