diff options
Diffstat (limited to 'packet.c')
| -rw-r--r-- | packet.c | 19 |
1 files changed, 11 insertions, 8 deletions
@@ -28,8 +28,6 @@ distinguish them from baud barf. #include <unistd.h> #include <string.h> #include <errno.h> -#include <sys/time.h> -#include <sys/ioctl.h> #include "config.h" #include "gpsd.h" @@ -57,14 +55,18 @@ void gpsd_report(int errlevel, const char *fmt, ... ) #endif /* TESTMAIN */ /* - * The packet-recognition state machine. It doesn't do checksums, - * caller is responsible for that part. It can be fooled by garbage + * The packet-recognition state machine. It can be fooled by garbage * that looks like the head of a binary packet followed by a NMEA * packet; in that case it won't reset until it notices that the * binary trailer is not where it should be, and the NMEA packet will * be lost. The reverse scenario is not possible because none of the * binary leader character can occur in an NMEA packet. Caller should * consume a packet when it sees one of the *_RECOGNIZED states. + * It's good practice to follow the _RECOGNIZED transition with one + * that recognizes a leader of the same packet type rather than + * dropping back to ground state -- this for example will prevent + * the state machine from hopping between recognizing TSIP and + * Evermore packets that both start with a DLE. * * Error handling is brutally simple; any time we see an unexpected * character, go to GROUND_STATE and reset the machine (except that a @@ -82,8 +84,9 @@ void gpsd_report(int errlevel, const char *fmt, ... ) enum { GROUND_STATE, /* we don't know what packet type to expect */ - NMEA_DOLLAR, /* we've seen first character of NMEA leader */ + /* NMEA 0183 packet states */ + NMEA_DOLLAR, /* we've seen first character of NMEA leader */ NMEA_PUB_LEAD, /* seen second character of NMEA G leader */ NMEA_LEADER_END, /* seen end char of NMEA leader, in body */ NMEA_CR, /* seen terminating \r of NMEA packet */ @@ -150,7 +153,7 @@ enum { EVERMORE_HEADER_DLE, /* 1-byte packet length was DLE */ EVERMORE_PAYLOAD, /* in payload part of Evermore packet */ EVERMORE_DELIVERED, /* got to end of payload, looking for checksum */ - EVERMORE_CHECKSUM_DLE, /* in payload part of Evermore packet */ + EVERMORE_SUM_DLE, /* in payload part of Evermore packet */ EVERMORE_TRAILER_1, /* looking for first byte of Evermore trailer */ EVERMORE_RECOGNIZED, /* found end of Evermore packet */ #endif /* EVERMORE_ENABLE */ @@ -491,11 +494,11 @@ static void nexstate(struct gps_device_t *session, unsigned char c) break; case EVERMORE_DELIVERED: if (c == 0x10) - session->packet_state = EVERMORE_CHECKSUM_DLE; + session->packet_state = EVERMORE_SUM_DLE; else session->packet_state = EVERMORE_TRAILER_1; break; - case EVERMORE_CHECKSUM_DLE: + case EVERMORE_SUM_DLE: if (c == 0x10) session->packet_state = EVERMORE_TRAILER_1; else |