diff options
| -rw-r--r-- | gpsmon.c | 14 | ||||
| -rw-r--r-- | ppsthread.c | 58 | ||||
| -rw-r--r-- | ppsthread.h | 2 | ||||
| -rw-r--r-- | timehint.c | 15 |
4 files changed, 68 insertions, 21 deletions
@@ -1322,14 +1322,16 @@ int main(int argc, char **argv) /* * The HAT kludge. If we're using the HAT GPS on a * Raspberry Pi or a workalike like the ODROIDC2, and - * there is a static /dev/pps0, and we have access because + * there is a static "first PPS", and we have access because * we're root, assume we want to use KPPS. */ - if ((strcmp(session.pps_thread.devicename, MAGIC_HAT_GPS) == 0 - || strcmp(session.pps_thread.devicename, MAGIC_LINK_GPS) == 0) - && access("/dev/pps0", R_OK | W_OK) == 0) - session.pps_thread.devicename = "/dev/pps0"; - #endif /* MAGIC_HAT_GPS && MAGIC_LINK_GPS */ + if (strcmp(session.pps_thread.devicename, MAGIC_HAT_GPS) == 0 + || strcmp(session.pps_thread.devicename, MAGIC_LINK_GPS) == 0) { + char *first_pps = pps_get_first(); + if (access(first_pps, R_OK | W_OK) == 0) + session.pps_thread.devicename = first_pps; + } + #endif /* MAGIC_HAT_ENABLE */ pps_thread_activate(&session.pps_thread); } #endif /* PPS_ENABLE */ diff --git a/ppsthread.c b/ppsthread.c index 428f1c8b..53a93b2e 100644 --- a/ppsthread.c +++ b/ppsthread.c @@ -66,7 +66,15 @@ * CONFIG_PPS=y * CONFIG_PPS_DEBUG=y [optional to kernel log pulses] * CONFIG_PPS_CLIENT_LDISC=y + * + * Also beware that setting + * CONFIG_PPS_CLIENT_KTIMER=y + * adds a fake software-generated PPS intended for testing. This + * doesn't even run at exactly 1Hz, so any attempt to use it for + * real timing is disastrous. Hence we try to avoid it. */ +#define FAKE_PPS_NAME "ktimer" + #if defined(HAVE_SYS_TIMEPPS_H) // include unistd.h here as it is missing on older pps-tools releases. // 'close' is not defined otherwise. @@ -156,6 +164,39 @@ static void thread_unlock(volatile struct pps_thread_t *pps_thread) } #if defined(HAVE_SYS_TIMEPPS_H) +#ifdef __linux__ +/* Obtain contents of specified sysfs variable; null string if failure */ +static void get_sysfs_var(const char *path, char *buf, size_t bufsize) +{ + buf[0] = '\0'; + int fd = open(path, O_RDONLY); + if ( 0 <= fd ) { + ssize_t r = read( fd, buf, bufsize -1); + if ( 0 < r ) { + buf[r - 1] = '\0'; /* remove trailing \x0a */ + } + (void)close(fd); + } +} + +/* Check to see whether the named PPS source is the fake one */ +int pps_check_fake(const char *name) { + char path[PATH_MAX] = ""; + char buf[32] = ""; + snprintf(path, sizeof(path), "/sys/devices/virtual/pps/%s/name", name); + get_sysfs_var(path, buf, sizeof(buf)); + return strcmp(buf, FAKE_PPS_NAME) == 0; +} + +/* Get first "real" PPS device, skipping the fake, if any */ +char *pps_get_first(void) +{ + if (pps_check_fake("pps0")) + return "/dev/pps1"; + return "/dev/pps0"; +} +#endif /* __linux__ */ + static int init_kernel_pps(struct inner_context_t *inner_context) /* return handle for kernel pps, or -1; requires root privileges */ { @@ -189,8 +230,14 @@ static int init_kernel_pps(struct inner_context_t *inner_context) * (We use strncpy() here because this might be compiled where * strlcpy() is not available.) */ - if (strncmp(pps_thread->devicename, "/dev/pps", 8) == 0) + if (strncmp(pps_thread->devicename, "/dev/pps", 8) == 0) { + if (pps_check_fake(pps_thread->devicename + 5)) + pps_thread->log_hook(pps_thread, THREAD_WARN, + "KPPS:%s is fake PPS," + " timing will be inaccurate\n", + pps_thread->devicename); (void)strncpy(path, pps_thread->devicename, sizeof(path)-1); + } else { char pps_num = '\0'; /* /dev/pps[pps_num] is our device */ size_t i; /* to match type of globbuf.gl_pathc */ @@ -227,14 +274,7 @@ static int init_kernel_pps(struct inner_context_t *inner_context) memset( (void *)&path, 0, sizeof(path)); for ( i = 0; i < globbuf.gl_pathc; i++ ) { - int fd = open(globbuf.gl_pathv[i], O_RDONLY); - if ( 0 <= fd ) { - ssize_t r = read( fd, path, sizeof(path) -1); - if ( 0 < r ) { - path[r - 1] = '\0'; /* remove trailing \x0a */ - } - (void)close(fd); - } + get_sysfs_var(globbuf.gl_pathv[i], path, sizeof(path)); pps_thread->log_hook(pps_thread, THREAD_PROG, "KPPS:%s checking %s, %s\n", pps_thread->devicename, diff --git a/ppsthread.h b/ppsthread.h index b37e739c..3d5f696e 100644 --- a/ppsthread.h +++ b/ppsthread.h @@ -53,5 +53,7 @@ extern void pps_thread_fixin(volatile struct pps_thread_t *, volatile struct timedelta_t *); extern int pps_thread_ppsout(volatile struct pps_thread_t *, volatile struct timedelta_t *); +int pps_check_fake(const char *); +char *pps_get_first(void); #endif /* PPSTHREAD_H */ @@ -463,14 +463,17 @@ void ntpshm_link_activate(struct gps_device_t *session) /* * The HAT kludge. If we're using the HAT GPS on a * Raspberry Pi or a workalike like the ODROIDC2, and - * there is a static /dev/pps0, and we have access because + * there is a static "first PPS", and we have access because * we're root, assume we want to use KPPS. */ - if ((strcmp(session->pps_thread.devicename, MAGIC_HAT_GPS) == 0 - || strcmp(session->pps_thread.devicename, MAGIC_LINK_GPS) == 0) - && access("/dev/pps0", R_OK | W_OK) == 0) - session->pps_thread.devicename = "/dev/pps0"; - #endif /* MAGIC_HAT_GPS && MAGIC_LINK_GPS */ + if (strcmp(session->pps_thread.devicename, MAGIC_HAT_GPS) == 0 + || strcmp(session->pps_thread.devicename, + MAGIC_LINK_GPS) == 0) { + char *first_pps = pps_get_first(); + if (access(first_pps, R_OK | W_OK) == 0) + session->pps_thread.devicename = first_pps; + } + #endif /* MAGIC_HAT_ENABLE */ pps_thread_activate(&session->pps_thread); } } |