[PATCH v4 5/9] spi: spidev_test: don't send 0x0 or 0xff

[Jonas Rebmann]

From: Marc Kleine-Budde <mkl@xxxxxxxxxxxxxx>

Particularly when using compare mode, if the controller fails to
transfer any data, asserting on a read of 0x00 or 0xff may lead a false
negative test, indicating a byte was successfully transferred when the
values simply originate from the pull-up or pull-down of RX.

Signed-off-by: Marc Kleine-Budde <mkl@xxxxxxxxxxxxxx>
Signed-off-by: Jonas Rebmann <jre@xxxxxxxxxxxxxx>
---
 tools/spi/spidev_test.c | 20 ++++++++++++++++----
 1 file changed, 16 insertions(+), 4 deletions(-)

diff --git a/tools/spi/spidev_test.c b/tools/spi/spidev_test.c
index 906f9997b10a..c34601558646 100644
--- a/tools/spi/spidev_test.c
+++ b/tools/spi/spidev_test.c
@@ -45,6 +45,7 @@ static int transfer_size;
 static int iterations;
 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 input_choices;
 
@@ -174,7 +175,7 @@ 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 [-2348CDFHILMNORSZbcdiloprstvw]\n", prog);
+	printf("Usage: %s [-2348CDFHILMNORSZbcdiloprstvwz]\n", prog);
 	puts("general device settings:\n"
 		 "  -D --device         device to use (default /dev/spidev1.1)\n"
 		 "  -s --speed          max speed (Hz)\n"
@@ -198,6 +199,7 @@ static void print_usage(const char *prog)
 		 "  -i --input          input data from a file (e.g. \"test.bin\")\n"
 		 "  -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"
 		 "  -S --size           transfer the given number of random bytes\n"
 		 "  -I --iter           iterations\n"
 		 "additional parameters:\n"
@@ -235,6 +237,7 @@ static void parse_opts(int argc, char *argv[])
 			{ "input",         1, 0, 'i' },
 			{ "output",        1, 0, 'o' },
 			{ "size",          1, 0, 'S' },
+			{ "nonzero",       0, 0, 'z' },
 			{ "iter",          1, 0, 'I' },
 			{ "bpw",           1, 0, 'b' },
 			{ "lsb",           0, 0, 'L' },
@@ -247,7 +250,7 @@ static void parse_opts(int argc, char *argv[])
 		};
 		int c;
 
-		c = getopt_long(argc, argv, "D:s:d:w:b:i:o:lctrHOLC3ZFMNR248p:vS:I:",
+		c = getopt_long(argc, argv, "D:s:d:w:b:i:o:lctrHOLC3ZFMNR248p:vS:zI:",
 				lopts, NULL);
 
 		if (c == -1)
@@ -339,6 +342,9 @@ static void parse_opts(int argc, char *argv[])
 			transfer_size = atoi(optarg);
 			input_choices++;
 			break;
+		case 'z':
+			nonzero = 1;
+			break;
 		case 'I':
 			iterations = atoi(optarg);
 			break;
@@ -441,8 +447,11 @@ static void transfer_buf(int fd, int len)
 		tx = malloc(len);
 		if (!tx)
 			pabort("can't allocate tx buffer");
-		for (i = 0; i < len; i++)
-			tx[i] = random();
+		for (i = 0; i < len; i++) {
+			do
+				tx[i] = random();
+			while (nonzero && (tx[i] == 0x0 || tx[i] == 0xff));
+		}
 	}
 
 	if (do_rx) {
@@ -481,6 +490,9 @@ int main(int argc, char *argv[])
 	if (input_choices > 1)
 		pabort("only one of -S (--size), -p, -i (--input), -t (--no-tx) may be selected");
 
+	if (nonzero && !transfer_size)
+		pabort("-z (--nonzero) is only implemented for -S (--size)");
+
 	if (compare && (!do_tx || !do_rx))
 		pabort("-c (--compare) conflicts with -t (--no-tx) or -r (--no-rx)");
 

-- 
2.56.0.rc0.108.gf0ef1b96a0