--- Begin Message ---
|
Subject: |
[PATCH] Add NetBSD support for RFC2783 PPS. |
|
Date: |
Sun, 24 Nov 2013 14:18:49 -0500 |
This commit rewrites the introductory comment to be OS-neutral, but
does not substantially change it for the "#ifdef linux" reader.
Add linux ifdefs around Linux-specific code, and add alternate code
for systems that use the serial port file descriptor for RFC2783
calls.
---
ppsthread.c | 94 ++++++++++++++++++++++++++++++++++++++++++++++++++++++-------
1 file changed, 84 insertions(+), 10 deletions(-)
diff --git a/ppsthread.c b/ppsthread.c
index fe1947b..668eb0a 100644
--- a/ppsthread.c
+++ b/ppsthread.c
@@ -4,12 +4,25 @@
* If you are not good at threads do not touch this file!
*
* It helps to know that there are two PPS measurement methods in
- * play. One, kernel PPS (KPPS), is RFC2783 and available on many
- * OS and supplied through special /dev/pps devices. The other, plain
- * PPS, uses the TIOCMIWAIT ioctl to explicitly watch for PPS on
- * serial lines. KPPS requires root permissions for initialization;
- * plain PPS does not. Plain PPS loses some functionality when not
- * initialized as root.
+ * play. One is defined by RFC2783 and typically implemented in the
+ * kernel. It is available on FreeBSD, Linux, and NetBSD. On Linux
+ * it is referred to as KPPS, and is accessed via /dev/ppsN devices.
+ * On BSD it is accessed via the same device as the serial port. This
+ * mechanism is preferred as it should provide the smallest latency
+ * and jitter from control line transition to timestamp.
+ *
+ * The other mechanism is user-space PPS, which uses the (not
+ * standardized) TIOCMIWAIT ioctl to wait for PPS transitions on
+ * serial port control lines. It is implemented on Linux and OpenBSD.
+ *
+ * On Linux, RFC2783 PPS requires root permissions for initialization;
+ * user-space PPS does not. User-space PPS loses some functionality
+ * when not initialized as root. In Linux, user-space PPS is referred
+ * to as "plain PPS".
+ *
+ * On {Free,Net}BSD, RFC2783 PPS should only require access to the
+ * serial port, but details have not yet been tested and documented
+ * here.
*
* To use the thread manager, you need to first fill in the two
* thread_* methods in the session structure and/or the pps_hook in
@@ -63,21 +76,42 @@ static pthread_mutex_t ppslast_mutex;
static int init_kernel_pps(struct gps_device_t *session)
/* return handle for kernel pps, or -1; requires root privileges */
{
- int ldisc = 18; /* the PPS line discipline */
#ifndef S_SPLINT_S
pps_params_t pp;
#endif /* S_SPLINT_S */
+ int ret;
+#ifdef linux
+ /* These variables are only needed by Linux to find /dev/ppsN. */
+ int ldisc = 18; /* the PPS line discipline */
glob_t globbuf;
size_t i; /* to match type of globbuf.gl_pathc */
char pps_num = '\0'; /* /dev/pps[pps_num] is our device */
char path[GPS_PATH_MAX] = "";
- int ret;
+#endif
session->kernelpps_handle = -1;
if ( isatty(session->gpsdata.gps_fd) == 0 ) {
gpsd_report(session->context->debug, LOG_INF, "KPPS gps_fd not a
tty\n");
return -1;
}
+
+ /*
+ * This next code block abuses "ret" by storing the filedescriptor
+ * to use for RFC2783 calls.
+ */
+ ret = -1;
+#ifndef linux
+ /*
+ * On BSDs that support RFC2783, one uses the API calls on serial
+ * port file descriptor.
+ */
+ ret = session->gpsdata.gps_fd;
+#else /* linux */
+ /*
+ * On Linux, one must make calls to associate a serial port with a
+ * /dev/ppsN device and then grovel in system data to determine
+ * the association.
+ */
/address@hidden@*/
/* Attach the line PPS discipline, so no need to ldattach */
/* This activates the magic /dev/pps0 device */
@@ -146,6 +180,12 @@ static int init_kernel_pps(struct gps_device_t *session)
"KPPS cannot open %s: %s\n", path, strerror(errno));
return -1;
}
+#endif
+ /* assert(ret >= 0); */
+ gpsd_report(session->context->debug, LOG_INF,
+ "RFC2783 fd is %d\n",
+ ret);
+
/* RFC 2783 implies the time_pps_setcap() needs priviledges *
* keep root a tad longer just in case */
if ( 0 > time_pps_create(ret, &session->kernelpps_handle )) {
@@ -166,9 +206,16 @@ static int init_kernel_pps(struct gps_device_t *session)
LOG_INF, "KPPS caps %0x\n", caps);
}
+#ifndef linux
+ /*
+ * Attempt to follow RFC2783 as straightforwardly as possible.
+ */
+ pp.mode = PPS_TSFMT_TSPEC | PPS_CAPTUREBOTH;
+#else /* linux */
/* linux 2.6.34 can not PPS_ECHOASSERT | PPS_ECHOCLEAR */
memset( (void *)&pp, 0, sizeof(pps_params_t));
pp.mode = PPS_CAPTUREBOTH;
+#endif
#endif /* S_SPLINT_S */
if ( 0 > time_pps_setparams(session->kernelpps_handle, &pp)) {
@@ -258,14 +305,36 @@ static /address@hidden@*/ void *gpsd_ppsmonitor(void *arg)
#if defined(HAVE_SYS_TIMEPPS_H) && !defined(S_SPLINT_S)
if ( 0 <= session->kernelpps_handle ) {
struct timespec kernelpps_tv;
+#ifndef linux
+ /*
+ * RFC2783 specifies that a NULL timeval means to wait.
+ */
+ kernelpps_tv.tv_sec = 1;
+ kernelpps_tv.tv_nsec = 0;
+#else
+ /*
+ * \todo Explain the use of a non-NULL zero timespec,
+ * which means to return immediately with -1 (section
+ * 3.4.3). Further, explain the non-sensical comment,
+ * because the intent of RFC2783 is that the timestamp has
+ * already been captured in the kernel, and we are merely
+ * fetching it here.
+ */
/* on a quad core 2.4GHz Xeon this removes about 20uS of
* latency, and about +/-5uS of jitter over the other method */
memset( (void *)&kernelpps_tv, 0, sizeof(kernelpps_tv));
+#endif
if ( 0 > time_pps_fetch(session->kernelpps_handle, PPS_TSFMT_TSPEC
, &pi, &kernelpps_tv)) {
gpsd_report(session->context->debug, LOG_ERROR,
"KPPS kernel PPS failed\n");
} else {
+ /* Wait until we have both edges. */
+ if (pi.assert_sequence == 0 || pi.clear_sequence == 0) {
+ usleep(100000);
+ continue;
+ }
+
// find the last edge
// FIXME a bit simplistic, should hook into the
// cycle/duration check below.
@@ -282,15 +351,20 @@ static /address@hidden@*/ void *gpsd_ppsmonitor(void *arg)
edge_kpps = 0;
ts_kpps = pi.clear_timestamp;
}
+ /*
+ * pps_seq_t is uint32_t on NetBSD, so cast to
+ * unsigned long as a wider-or-equal type to
+ * accomodate Linux's type.
+ */
gpsd_report(session->context->debug, LOG_PROG,
"KPPS assert %ld.%09ld, sequence: %ld - "
"clear %ld.%09ld, sequence: %ld\n",
pi.assert_timestamp.tv_sec,
pi.assert_timestamp.tv_nsec,
- pi.assert_sequence,
+ (unsigned long) pi.assert_sequence,
pi.clear_timestamp.tv_sec,
pi.clear_timestamp.tv_nsec,
- pi.clear_sequence);
+ (unsigned long) pi.clear_sequence);
gpsd_report(session->context->debug, LOG_PROG,
"KPPS data: using %s\n",
edge_kpps ? "assert" : "clear");
--
1.8.4
--- End Message ---