[RFC libevdev] Enable event logging for debugging

[David Herrmann]

Hi

On Thu, Apr 3, 2014 at 12:30 PM, Peter Hutterer
<peter.hutterer at who-t.net> wrote:
> This is a new approach to an earlier patch [1]. I'm running into more
> use-cases where I really need the event sequence the caller sees to figure
> out where the bug is. Note that the patch is just lightly tested, this is an
> early RFC.
>
> I'll just copy the documentation here, that explains what I'm trying to do:
>
> + * libevdev checks the LIBEVDEV_LOG_EVENTS environment variable. If set to
> + * "error", "info", or "debug", all events are logged with the respective
> + * priority before they are passed to the client. This is useful to check
> + * event sequences that happen before a specific bug in the higher layers of
> + * the stack
> + *
> + * To debug specific devices only, the minor numbers of the device node may
> + * be provided as a comma-separated list after the priority:
> + * LIBEVDEV_LOG_EVENTS="error:1,2,3" logs all events from the devices with a
> + * minor number 1, 2 or 3. The minor number comparison is performed on
> + * libevdev_set_fd() and libevdev_change_fd().
> + *
> + * Since event logged by libevdev are likely to end up in some files and are
> + * potentially attached to public bug reports, key event codes are
> + * obfuscated to protect accidental leakage of private information. Key
> + * codes between KEY_ESC up to including KEY_STOP are always logged as
> + * "OBFUSCATED".
> + *
>
> This should address some of the comments on the previous revision. It makes
> it easier to debug a specific device only to cut down on the log spam. And
> some of the security issues are alleviated by obfuscating key codes (I also
> need to do this for MSC_SCAN) so that a password doesn't accidentally end up
> in bugzilla somewhere.
>
> Comments?

TBH, I don't really care. With structured-logging and journald, you
can pass the device-node as ancillary data. This way, I can just use
"journalctl DEVICE_NODE=eventXYZ" to filter for the device (or
something similar..). But the patch looks fine to me.

Thanks
David