ubb-patgen/ubb-patgen.c: new option -i to select frequency by cycle time

ubb-patgen/README

@@ -63,6 +63,14 @@ bus clk = 100.962 kHz (+0.96%)
 
 This warning can be suppressed with the option -q.
 
+The frequency can also be specified as the cycle time with the
+option -i:
+
+# ubb-patgen -i 10us
+
+The meaning of an appended + or - changes here, e.g., 10us+
+selects a slower clock (producing an interval of at least 10 us).
+
 
 Clock output
 ------------

ubb-patgen/ubb-patgen.c

@@ -506,7 +506,7 @@ static int frequency(const char *s, int *hz, int *rel)
 }
 
 
-static int duration(const char *s, struct timespec *res)
+static int duration(const char *s, double *res, int *rel)
 {
 	char *end;
 	double d;
@@ -539,12 +539,49 @@ static int duration(const char *s, struct timespec *res)
 	if (*end == 'S' || *end == 's')
 		end++;
 
+	switch (*end) {
+	case '+':
+		*rel = 1;
+		end++;
+		break;
+	case '-':
+		*rel = -1;
+		end++;
+		break;
+	default:
+		*rel = 0;
+		break;
+	}
+
 	if (*end)
 		return 0;
 
+	*res = d;
+
+	return 1;
+}
+
+
+static int duration_timespec(const char *s, struct timespec *res, int *rel)
+{
+	double d;
+
+	if (!duration(s, &d, rel))
+		return 0;
 	res->tv_sec = d;
 	res->tv_nsec = (d-res->tv_sec)*1e9;
+	return 1;
+}
 
+
+static int interval(const char *s, int *hz, int *rel)
+{
+	double d;
+
+	if (!duration(s, &d, rel))
+		return 0;
+	*hz = 1/d;
+	*rel = -*rel;
 	return 1;
 }
 
@@ -553,12 +590,15 @@ static void usage(const char *name)
 {
         fprintf(stderr,
 "usage: %s\n"
-"       %s [-q] -f freq_hz\n"
+"       %s [-q] -f freq_hz|-i interval_s\n"
-"       %s [-q] [-f freq_hz] -c [active_s]\n"
+"       %s [-q] [-f freq_hz|-i interval_s] -c [active_s]\n"
-"       %s [-q] [-f freq_hz] [-C|-t 0|1] [-m mask] [-p] file|pattern\n\n"
+"       %s [-q] [-f freq_hz|-i interval_s] [-C|-t 0|1] [-m mask] [-p]\n"
+"          file|pattern\n\n"
 "  -c          output bus clock on CLK without sending a pattern\n"
 "  -C          temporarily output bus clock on CLK (for debugging)\n"
 "  -f freq_hz  set bus clock to the specified frequency (default: 1 MHz)\n"
+"  -i inter_s  set bus clock such that one cycle equals the specified "
+  "interval\n"
 "  -m mask     use only the DATx lines specified in the mask (default: 0xf)\n"
 "  -p          force interpretation of argument as pattern (and not file)\n"
 "  -q          quiet. Don't pretty-print frequencies; don't report clock\n"
@@ -574,7 +614,8 @@ static void usage(const char *name)
 "  \"+\" selects a frequency >= the specified one, \"-\" one <=.\n"
 "  Without +/-, the closest available frequency is selected.\n"
 "Duration: the duration in seconds, optionally followed by \"m\", \"u\", or\n"
-"  \"n\", optionally followed by \"s\".\n"
+"  \"n\", optionally followed by \"s\", optionally followed by \"+\" or \"-\"."
+  "\n"
 "Pattern: hex digits corresponding to 1 for DAT0, 2 for DAT1, etc.\n"
 "  {n} repeats the preceding digit n times, e.g., 1{3} is equivalent to 111.\n"
     , name, name, name, name);
@@ -589,6 +630,7 @@ int main(int argc, char **argv)
 	const char *pattern = NULL;
 	int quiet = 0, force_pattern = 0;
 	struct timespec active_ns;
+	int active_rel = 0;
 	int keep_clk = 1;
 	uint8_t mask = 0xf;
 	int trigger = -1;
@@ -596,12 +638,16 @@ int main(int argc, char **argv)
 	int c;
 	unsigned long tmp;
 
-	while ((c = getopt(argc, argv, "cCf:m:pqt:")) != EOF)
+	while ((c = getopt(argc, argv, "cCf:i:m:pqt:")) != EOF)
 		switch (c) {
 		case 'f':
 			if (!frequency(optarg, &bus_hz, &bus_rel))
 				usage(*argv);
 			break;
+		case 'i':
+			if (!interval(optarg, &bus_hz, &bus_rel))
+				usage(*argv);
+			break;
 		case 'c':
 			clk_only = 1;
 			break;
@@ -664,7 +710,10 @@ int main(int argc, char **argv)
 		if (clk_only) {
 			if (force_pattern)
 				usage(*argv);
-			if (!duration(argv[optind], &active_ns))
+			if (!duration_timespec(argv[optind],
+			    &active_ns, &active_rel))
+				usage(*argv);
+			if (active_rel < 0)
 				usage(*argv);
 			keep_clk = 0;
 		} else {