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List:       gpsd-dev
Subject:    Re: [Gpsd-dev] [Gpsd-users]  Preparing for 2.93 point release
From:       Eric Raymond <esr () thyrsus ! com>
Date:       2010-07-14 8:12:38
Message-ID: 20100714081238.GA8254 () thyrsus ! com
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wheresmyhat <wheresmyhat@lavabit.com>:
> My platform is Ubuntu 10.04, gpsd and gpsd-clients upgraded to release
> 2.94_2 from debian unstable:
> - Linux 2.6.32-23-generic #37-Ubuntu SMP Fri Jun 11 08:03:28 UTC 2010 x86_64
> GNU/Linux
> - gpsd: 2.94 (revision 2010-05-09T23:34:56)
> 
> My GPS receiver is a BU-353 (USB): native mode is SiRF, and also supports
> NMEA 0183.
> 
> The gpsmon client works fluently when the receiver is in SiRF binary mode,
> and accessed directly through /dev/ttyUSB0 (no gpsd involved). In this case
> I don't even notice the CPU load reported by Hakan.
> 
> When the receiver is in SiRF binary mode, but accessed via gpsd, the gpsmon
> client fails immediatly with "Read error from device".
> I've uploaded the result of sudo strace -oSiRF.gpsd.strace gpsmon: 
> http://old.nabble.com/file/p28951035/SiRF.gpsd.strace SiRF.gpsd.strace 
> 
> When the receiver is set to NMEA mode, and accessed via gpsd, the gpsmon
> client also fails immediatly with "Read error from device".
> I've uploaded the result of sudo strace -oNMEA.gpsd.strace gpsmon: 
> http://old.nabble.com/file/p28951035/NMEA.gpsd.strace NMEA.gpsd.strace 
> 
> When the receiver is set to NMEA mode, and accessed directly through
> /dev/ttyUSB0, the gpsmon client fails with "Read error from device", but
> after a few seconds of normal activity.
> I've uploaded the result of sudo strace -oNMEA.direct.strace gpsmon
> /dev/ttyUSB0:  http://old.nabble.com/file/p28951035/NMEA.direct.strace
> NMEA.direct.strace 
> 
> Rem: To set the receiver to NMEA mode, I had to bypass the daemon.
> $ sudo gpsctl -f -n /dev/ttyUSB0 
> gpsctl: /dev/ttyUSB0 identified as a SiRF binary at 4800.
> gpsctl: switching to mode NMEA.
> gpsctl: after mode change, /dev/ttyUSB0 looks like a Generic NMEA
> GSW3.2.4_3.1.00.12-SDK003P1.00a  at 4800.

We just shipped 2.95, which includes some subtle changes in the way 
zero-length reads from devices are handled. It is possible this will
solve your problem.  If not, knowing if the behasvior you're seeing
has *changed* might help us isolate the problem.
-- 
		<a href="http://www.catb.org/~esr/">Eric S. Raymond</a>
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