fixup! Add strptime(3).

Waiting for any non-zero duration currently waits for at least one timer
cycle (10 ms), which is especially expensive during early boot.

The current workaround of simply reading the status 14 times seems really
suspicious although the osdev wiki documents it, but let's see how well it
works on real hardware, it's probably good enough.

Try to determine the initial selected drive to save one drive selection.

libc/time/strptime.c

@@ -24,6 +24,11 @@
 #include <string.h>
 #include <time.h>
 
+#ifdef TEST
+#include <stdio.h>
+#define strptime mystrptime
+#endif
+
 static const char* wdays[] = {"Sunday", "Monday", "Tuesday", "Wednesday",
                               "Thursday", "Friday", "Saturday", NULL};
 static const char* months[] = {"January", "February", "March", "April", "May",
@@ -232,3 +237,78 @@ char* strptime(const char* restrict str,
 	}
 	return (char*) str;
 }
+
+#ifdef TEST
+#undef strptime
+
+#include <err.h>
+#include <stdio.h>
+
+int main(int argc, char* argv[])
+{
+	if ( argc < 3 )
+		err(1, "usage");
+	const char* str = argv[1];
+	const char* format = argv[2];
+	struct tm my_tm = {0};
+	char* my_end = mystrptime(str, format, &my_tm);
+	struct tm c_tm = {0};
+	char* c_end = strptime(str, format, &c_tm);
+	if ( !my_end && c_end )
+		errx(1, "rejected but c allowed it");
+	else if ( !my_end  )
+		errx(1, "rejected correctly");
+	else if ( !c_end )
+		printf("allowed but c rejected\n");
+	else if ( my_end != c_end )
+		errx(1, "mismatch my end \"%s\" vs c end \"%s\"", my_end, c_end);
+
+	if ( my_tm.tm_sec == c_tm.tm_sec )
+		printf("tm_sec=%i\n", my_tm.tm_sec);
+	else
+		printf("tm_sec=%i but C is %i\n", my_tm.tm_sec, c_tm.tm_sec);
+
+	if ( my_tm.tm_min == c_tm.tm_min )
+		printf("tm_min=%i\n", my_tm.tm_min);
+	else
+		printf("tm_min=%i but C is %i\n", my_tm.tm_min, c_tm.tm_min);
+
+	if ( my_tm.tm_hour == c_tm.tm_hour )
+		printf("tm_hour=%i\n", my_tm.tm_hour);
+	else
+		printf("tm_hour=%i but C is %i\n", my_tm.tm_hour, c_tm.tm_hour);
+
+	if ( my_tm.tm_mday == c_tm.tm_mday )
+		printf("tm_mday=%i\n", my_tm.tm_mday);
+	else
+		printf("tm_mday=%i but C is %i\n", my_tm.tm_mday, c_tm.tm_mday);
+
+	if ( my_tm.tm_mon == c_tm.tm_mon )
+		printf("tm_mon=%i\n", my_tm.tm_mon);
+	else
+		printf("tm_mon=%i but C is %i\n", my_tm.tm_mon, c_tm.tm_mon);
+
+	if ( my_tm.tm_year == c_tm.tm_year )
+		printf("tm_year=%i\n", my_tm.tm_year);
+	else
+		printf("tm_year=%i but C is %i\n", my_tm.tm_year, c_tm.tm_year);
+
+	if ( my_tm.tm_wday == c_tm.tm_wday )
+		printf("tm_wday=%i\n", my_tm.tm_wday);
+	else
+		printf("tm_wday=%i but C is %i\n", my_tm.tm_wday, c_tm.tm_wday);
+
+	if ( my_tm.tm_yday == c_tm.tm_yday )
+		printf("tm_yday=%i\n", my_tm.tm_yday);
+	else
+		printf("tm_yday=%i but C is %i\n", my_tm.tm_yday, c_tm.tm_yday);
+
+	if ( my_tm.tm_isdst == c_tm.tm_isdst )
+		printf("tm_isdst=%i\n", my_tm.tm_isdst);
+	else
+		printf("tm_isdst=%i but C is %i\n", my_tm.tm_isdst, c_tm.tm_isdst);
+
+	return 0;
+}
+
+#endif