[maemo-users] Accessing GPS on Nokia N810

From: Petr Stetiar ynezz at true.cz
Date: Tue Mar 11 10:43:20 EET 2008
Tuomas Kulve <tuomas at kulve.fi> [2008-03-11 10:26:50]:

> Petr Stetiar wrote:
> > Because 'gpsdriver' seems to be some kind of middleware between userspace
> > applications and kernel driver. It powers On/Off the GPS, uploads also
> How does it power the GPS on/off? I.e. how do you ask it to do it?

That's what I want to find out. I'm quite lost in strace's output, since
there are some unknown syscalls used like SYS_284 and SYS_285, and I didn't
find out what they're yet. I don't have the systrace's output here, but it's
something like this - if for example 'navicore' want access to GPS, it write's
somehow 'P 3\n' to gpsdriver and gpsdriver powers on GPS using GPS GPIO's in
/sys (you can find them easily by using strings on gpsdriver binary), uploads
nvd_data file, creates /dev/pts/X device and makes /dev/pgps symlink to it and
then starts gpsd daemon using this /dev/pgps device. Then if 'navicore' don't
want to use GPS device, so it writes 'P 0\n' to gpsdriver somehow and gpsdriver
powers off the GPS device.

-- ynezz

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