Hi On Wed, Oct 29, 2014 at 3:45 PM, Bastien Nocera <had...@hadess.net> wrote: > For a very specific definition of inactive. > > I'm looking at a way for the iio-sensor-proxy at: > https://github.com/hadess/iio-sensor-proxy > to suspend reading from accelerometers (or maybe to turn them off), when > all the sessions are locked and the screens turned off. > > This would usually mean that I would enable reading from the sensor if > one session is "active" and stop reading if none are "active". Is this > correct? Is it up to the session manager (eg. gnome-session) to tell us > whether a session is active or not, or do I have this backwards?
For uhid (similar to uinput) you get an OPEN and CLOSE event whenever the first/last user opens/closes the device you created. I think we want something similar for uinput. That is, when a gnome session is inactive, they should just close the input devices that were created by iio-sensor-proxy (done automatically if you use the systemd-logind API to access devices). This way, iio-sensor-proxy knows whenever at least one session uses the data. This is also how most kernel-internal APIs work. This way, iio-sensor-proxy would get an OPEN event if at least one user reads the data it produces, and a CLOSE event once the last user closed the device. Unfortunately, this requires kernel changes, which you probably want to avoid. But a user-space solution sounds like a hack to me. You'd have to somehow 'guess' whether there's a user of your input device. Not sure how to make that reliable.. I wrote something up: https://gist.github.com/dvdhrm/6af5b000ddaed781764c I can try to send this to linux-input@vger today. One downside is that there's no way to synchronously query iio-sensor-proxy to provide the needed information on wake-up. That is, if the screen is turned on but iio-sensor-proxy is suspended, then the first frame might be displayed in the wrong layout. If iio-sensor-proxy was a kernel driver, this wouldn't happen. Similarly, if it provided a dbus API, gnome could query it synchronously on wake-up. I could make the UI_EV_OPEN event synchronous, but that seems overkill to me... hmm, not sure. Thanks David _______________________________________________ systemd-devel mailing list systemd-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/systemd-devel
