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| author | Eric S. Raymond <esr@thyrsus.com> | 2005-03-12 16:41:53 +0000 |
|---|---|---|
| committer | Eric S. Raymond <esr@thyrsus.com> | 2005-03-12 16:41:53 +0000 |
| commit | 7c10961464c8015f5c1e3c029e8f0910ee80a50b (patch) | |
| tree | 47cccbd02e25b79c4857d63585d2cf84d118c1b6 /HACKING | |
| parent | 7e0142912fca9c51a1ab2294ad80c086c1677197 (diff) | |
| download | gpsd-7c10961464c8015f5c1e3c029e8f0910ee80a50b.tar.gz | |
Outlinize the HACKING file.
Diffstat (limited to 'HACKING')
| -rw-r--r-- | HACKING | 27 |
1 files changed, 17 insertions, 10 deletions
@@ -1,6 +1,9 @@ - Hacker's Guide to gpsd +This is the Hacker's Guide to gpsd. If you're viewing it with Emacs, try +doing Ctl-C Ctl-t and browsing through the outline headers. -First, debugging... +If you're looking for things to hack on, first see the TODO file. + +** Debugging For debugging purposes, it may be helpful to configure with --disable-shared. This turns off all the shared-library crud, making it somewhat easier to @@ -11,7 +14,11 @@ to strip clean NMEA out of the log files produced by gpsd. This can be useful if someone ships you a log that they allege caused gpsd to misbehave. -Next, profiling... +gpsfake enables you to repeatedly feed a packet sequence to a gpsd +instance running as non-root. Watching such a session with gdb should +smoke out ant repeatable bug pretty quickly. + +** Profiling There is a barely-documented Z command in the daemon will cause it to emit a $ clause on every D request. The $ clause contains four @@ -46,7 +53,7 @@ daemon to client library -- and to estimate the portion of the latency induced by serial transmit time. The gpsprof script creates latency plots using gnuplot(1). It can also report the raw data. -Then, architecture and how to hack it... +** Architecture and how to hack it This is not a complicated piece of code. Essentially, it spins in a loop polling for input from one of three sources: @@ -94,7 +101,7 @@ of the file-descriptor set representing the GPS would tell us if there were input waiting. The explicit test is there for other programs that might call gps_poll() without such a guarantee. -Next, autoconfiguration... +** Autoconfiguration One of the design goals for gpsd is to be as near zero-configuration as possible. Under most circumstances, it doesn't require either @@ -133,7 +140,7 @@ specified. Presently, here's how the autoconfig works. The outcome is that we know exactly what we're looking at, without any driver or baud rate options. -Adding new GPS types... +** Adding new GPS types Almost all GPSes speak NMEA 0183. However, it may occasionally be necessary to add support for some odd binary format. We're told that the hex dump @@ -163,7 +170,7 @@ These are strings which should elicit an identifying response from the GPS that you can use as a trigger string for a driver. This is how we detect SiRF chips (see step 5 under autoconfiguration above). -And more... - -If you're looking for things to hack on, first see the TODO file. - +Local variables: +mode: outline +paragraph-separate: "[ ]*$" +end: |