Date: Tue, 05 Feb 2013 21:41:38 -0700 From: Ian Lepore <ian@FreeBSD.org> To: "freebsd-hackers@freebsd.org" <freebsd-hackers@FreeBSD.org> Subject: Request for review, time_pps_fetch() enhancement Message-ID: <1360125698.93359.566.camel@revolution.hippie.lan>
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I'd like feedback on the attached patch, which adds support to our
time_pps_fetch() implementation for the blocking behaviors described in
section 3.4.3 of RFC 2783. The existing implementation can only return
the most recently captured data without blocking. These changes add the
ability to block (forever or with timeout) until a new event occurs.
-- Ian
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Index: sys/kern/kern_tc.c
===================================================================
--- sys/kern/kern_tc.c (revision 246337)
+++ sys/kern/kern_tc.c (working copy)
@@ -1446,6 +1446,50 @@
* RFC 2783 PPS-API implementation.
*/
+static int
+pps_fetch(struct pps_fetch_args *fapi, struct pps_state *pps)
+{
+ int err, timo;
+ pps_seq_t aseq, cseq;
+ struct timeval tv;
+
+ if (fapi->tsformat && fapi->tsformat != PPS_TSFMT_TSPEC)
+ return (EINVAL);
+
+ /*
+ * If no timeout is requested, immediately return whatever values were
+ * most recently captured. If timeout seconds is -1, that's a request
+ * to block without a timeout. WITNESS won't let us sleep forever
+ * without a lock (we really don't need a lock), so just repeatedly
+ * sleep a long time.
+ */
+ if (fapi->timeout.tv_sec || fapi->timeout.tv_nsec) {
+ if (fapi->timeout.tv_sec == -1)
+ timo = 0x7fffffff;
+ else {
+ tv.tv_sec = fapi->timeout.tv_sec;
+ tv.tv_usec = fapi->timeout.tv_nsec / 1000;
+ timo = tvtohz(&tv);
+ }
+ aseq = pps->ppsinfo.assert_sequence;
+ cseq = pps->ppsinfo.clear_sequence;
+ while (aseq == pps->ppsinfo.assert_sequence &&
+ cseq == pps->ppsinfo.clear_sequence) {
+ err = tsleep(pps, PCATCH, "ppsfch", timo);
+ if (err == EWOULDBLOCK && fapi->timeout.tv_sec == -1) {
+ continue;
+ } else if (err != 0) {
+ return (err);
+ }
+ }
+ }
+
+ pps->ppsinfo.current_mode = pps->ppsparam.mode;
+ fapi->pps_info_buf = pps->ppsinfo;
+
+ return (0);
+}
+
int
pps_ioctl(u_long cmd, caddr_t data, struct pps_state *pps)
{
@@ -1485,13 +1529,7 @@
return (0);
case PPS_IOC_FETCH:
fapi = (struct pps_fetch_args *)data;
- if (fapi->tsformat && fapi->tsformat != PPS_TSFMT_TSPEC)
- return (EINVAL);
- if (fapi->timeout.tv_sec || fapi->timeout.tv_nsec)
- return (EOPNOTSUPP);
- pps->ppsinfo.current_mode = pps->ppsparam.mode;
- fapi->pps_info_buf = pps->ppsinfo;
- return (0);
+ return (pps_fetch(fapi, pps));
#ifdef FFCLOCK
case PPS_IOC_FETCH_FFCOUNTER:
fapi_ffc = (struct pps_fetch_ffc_args *)data;
@@ -1540,7 +1578,7 @@
void
pps_init(struct pps_state *pps)
{
- pps->ppscap |= PPS_TSFMT_TSPEC;
+ pps->ppscap |= PPS_TSFMT_TSPEC | PPS_CANWAIT;
if (pps->ppscap & PPS_CAPTUREASSERT)
pps->ppscap |= PPS_OFFSETASSERT;
if (pps->ppscap & PPS_CAPTURECLEAR)
@@ -1680,6 +1718,9 @@
hardpps(tsp, ts.tv_nsec + 1000000000 * ts.tv_sec);
}
#endif
+
+ /* Wakeup anyone sleeping in pps_fetch(). */
+ wakeup(pps);
}
/*
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