ptp: add testptp mask test

Add option to test timestamp event queue mask manipulation in testptp.

Option -F allows the user to specify a single channel that will be
applied on the mask filter via IOCTL.

The test program will maintain the file open until user input is
received.

This allows checking the effect of the IOCTL in debugfs.

eg:

Console 1:
```
Channel 12 exclusively enabled. Check on debugfs.
Press any key to continue
```

Console 2:
```
0x00000000 0x00000001 0x00000000 0x00000000 0x00000000 0x00000000
0x00000000 0x00000000 0x00000000 0x00000000 0x00000000 0x00000000
0x00000000 0x00000000 0x00000000 0x00000000 0x00000000 0x00000000
0x00000000 0x00000000 0x00000000 0x00000000 0x00000000 0x00000000
0x00000000 0x00000000 0x00000000 0x00000000 0x00000000 0x00000000
0x00000000 0x00000000 0x00000000 0x00000000 0x00000000 0x00000000
0x00000000 0x00000000 0x00000000 0x00000000 0x00000000 0x00000000
0x00000000 0x00000000 0x00000000 0x00000000 0x00000000 0x00000000
0x00000000 0x00000000 0x00000000 0x00000000 0x00000000 0x00000000
0x00000000 0x00000000 0x00000000 0x00000000 0x00000000 0x00000000
0x00000000 0x00000000 0x00000000 0x00000000
```

Signed-off-by: Xabier Marquiegui <[e-mail]>
Suggested-by: Richard Cochran <[e-mail]>
Suggested-by: Vinicius Costa Gomes <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

tools/testing/selftests/ptp/testptp.c

···
 		" -d name    device to open\n"
 		" -e val     read 'val' external time stamp events\n"
 		" -f val     adjust the ptp clock frequency by 'val' ppb\n"
+		" -F chan    Enable single channel mask and keep device open for debugfs verification.\n"
 		" -g         get the ptp clock time\n"
 		" -h         prints this message\n"
 		" -i val     index for event/trigger\n"
···
 	int pps = -1;
 	int seconds = 0;
 	int settime = 0;
+	int channel = -1;
 
 	int64_t t1, t2, tp;
 	int64_t interval, offset;
···
 
 	progname = strrchr(argv[0], '/');
 	progname = progname ? 1+progname : argv[0];
-	while (EOF != (c = getopt(argc, argv, "cd:e:f:ghH:i:k:lL:n:o:p:P:sSt:T:w:x:Xz"))) {
+	while (EOF != (c = getopt(argc, argv, "cd:e:f:F:ghH:i:k:lL:n:o:p:P:sSt:T:w:x:Xz"))) {
 		switch (c) {
 		case 'c':
 			capabilities = 1;
···
 			break;
 		case 'f':
 			adjfreq = atoi(optarg);
+			break;
+		case 'F':
+			channel = atoi(optarg);
 			break;
 		case 'g':
 			gettime = 1;
···
 		}
 
 		free(xts);
+	}
+
+	if (channel >= 0) {
+		if (ioctl(fd, PTP_MASK_CLEAR_ALL)) {
+			perror("PTP_MASK_CLEAR_ALL");
+		} else if (ioctl(fd, PTP_MASK_EN_SINGLE, (unsigned int *)&channel)) {
+			perror("PTP_MASK_EN_SINGLE");
+		} else {
+			printf("Channel %d exclusively enabled. Check on debugfs.\n", channel);
+			printf("Press any key to continue\n.");
+			getchar();
+		}
 	}
 
 	close(fd);