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Re: [gpsd-dev] gpsd processor load

From: Gary E. Miller
Subject: Re: [gpsd-dev] gpsd processor load
Date: Thu, 31 Oct 2013 10:06:17 -0700

Yo Håkan!

On Thu, 31 Oct 2013 09:14:44 +0100
Håkan Johansson <address@hidden> wrote:

> Loose thoughts:

Loose replies...

> Question: the reason for having the PPS thread in the first place is
> that not that one cannot mix the select() and TIOCMIWAIT waiting in
> the main thread?

They are waking on different things.  select() is waiting on serial
data available.  TIOCMIWAIT is waiting on control line changes.

If we just check the control lines on select() wakeup  the measured
time of control line change may be off almost a second.

> If the BSDs really do tell about line changes by a 'spurious'
> select() event, then perhaps one should not use a separate thread at
> all and put the line change check (i.e. TIOCMGET) in the main thread.

or use time_pps_fetch() wis is designed for the purpose.

> This might not work for the short (microsecond) pulses.

Which time_pps_fecth() is designed to catch.

Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97701
        address@hidden  Tel:+1(541)382-8588

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