[PATCH v4 6/9] spi: spidev_test: send predictable data

[Jonas Rebmann]

From: Marc Kleine-Budde <mkl@xxxxxxxxxxxxxx>

Introduce a flag to test on a predictable byte sequence instead of
random bytes. This is useful when comparing multiple runs with the same
option set e.g. with an oscilloscope.

Signed-off-by: Marc Kleine-Budde <mkl@xxxxxxxxxxxxxx>
Signed-off-by: Jonas Rebmann <jre@xxxxxxxxxxxxxx>
---
 tools/spi/spidev_test.c | 23 +++++++++++++++++------
 1 file changed, 17 insertions(+), 6 deletions(-)

diff --git a/tools/spi/spidev_test.c b/tools/spi/spidev_test.c
index c34601558646..21a631d346a4 100644
--- a/tools/spi/spidev_test.c
+++ b/tools/spi/spidev_test.c
@@ -47,6 +47,7 @@ static int interval = 5; /* interval in seconds for showing transfer rate */
 static int compare;
 static int nonzero;
 static int do_tx = 1, do_rx = 1;
+static int predictable;
 static int input_choices;
 
 static uint8_t default_tx[] = {
@@ -175,7 +176,7 @@ static void transfer(int fd, uint8_t const *tx, uint8_t const *rx, size_t len)
 
 static void print_usage(const char *prog)
 {
-	printf("Usage: %s [-2348CDFHILMNORSZbcdiloprstvwz]\n", prog);
+	printf("Usage: %s [-2348CDFHILMNOPRSZbcdiloprstvwz]\n", prog);
 	puts("general device settings:\n"
 		 "  -D --device         device to use (default /dev/spidev1.1)\n"
 		 "  -s --speed          max speed (Hz)\n"
@@ -200,6 +201,7 @@ static void print_usage(const char *prog)
 		 "  -o --output         output data to a file (e.g. \"results.bin\")\n"
 		 "  -p                  send data (e.g. \"1234\\xde\\xad\")\n"
 		 "  -z --nonzero        don't send 0x00 or 0xff bytes\n"
+		 "  -P --predictable    send a predictable sequence instead of random numbers\n"
 		 "  -S --size           transfer the given number of random bytes\n"
 		 "  -I --iter           iterations\n"
 		 "additional parameters:\n"
@@ -245,12 +247,13 @@ static void parse_opts(int argc, char *argv[])
 			{ "no-cs",         0, 0, 'N' },
 			{ "ready",         0, 0, 'R' },
 			{ "mosi-idle-low", 0, 0, 'M' },
+			{ "predictable",   0, 0, 'P' },
 			{ "verbose",       0, 0, 'v' },
 			{ NULL, 0, 0, 0 },
 		};
 		int c;
 
-		c = getopt_long(argc, argv, "D:s:d:w:b:i:o:lctrHOLC3ZFMNR248p:vS:zI:",
+		c = getopt_long(argc, argv, "D:s:d:w:b:i:o:lctrHOLC3ZFMNR248p:PvS:zI:",
 				lopts, NULL);
 
 		if (c == -1)
@@ -329,6 +332,10 @@ static void parse_opts(int argc, char *argv[])
 			input_tx = optarg;
 			input_choices++;
 			break;
+		case 'P':
+			predictable = 1;
+			input_choices++;
+			break;
 		case '2':
 			mode |= SPI_TX_DUAL;
 			break;
@@ -448,9 +455,13 @@ static void transfer_buf(int fd, int len)
 		if (!tx)
 			pabort("can't allocate tx buffer");
 		for (i = 0; i < len; i++) {
-			do
-				tx[i] = random();
-			while (nonzero && (tx[i] == 0x0 || tx[i] == 0xff));
+			if (predictable) {
+				tx[i] = i - iterations;
+			} else {
+				do {
+					tx[i] = random();
+				} while (nonzero && (tx[i] == 0x0 || tx[i] == 0xff));
+			}
 		}
 	}
 
@@ -488,7 +499,7 @@ int main(int argc, char *argv[])
 	parse_opts(argc, argv);
 
 	if (input_choices > 1)
-		pabort("only one of -S (--size), -p, -i (--input), -t (--no-tx) may be selected");
+		pabort("only one of -S (--size), -p, -i (--input), -t (--no-tx), -P (--predictable) may be selected");
 
 	if (nonzero && !transfer_size)
 		pabort("-z (--nonzero) is only implemented for -S (--size)");

-- 
2.56.0.rc0.108.gf0ef1b96a0