$ diff spidev_test.c.orig spidev_test.c
24a25
> #include <assert.h>
44a46,47
> static uint8_t word_delay;
> static uint16_t pause_us;
128a132
> 		.word_delay_usecs = word_delay,
175c179
< 	printf("Usage: %s [-2348CDFHILMNORSZbdilopsv]\n", prog);
---
> 	printf("Usage: %s [-2348CDFHILMNORSZbdwPilopsv]\n", prog);
179a184,185
> 	         "  -w --word_delay     word_delay (usec)\n"
> 	         "  -P --pause          pause (usec)\n"
215a222,223
> 			{ "word_delay",    1, 0, 'w' },
> 			{ "pause",         1, 0, 'P' },
240c248
< 		c = getopt_long(argc, argv, "D:s:d:b:i:o:lHOLC3ZFMNR248p:vS:I:",
---
> 		c = getopt_long(argc, argv, "D:s:d:w:P:b:i:o:lHOLC3ZFMNR248p:vS:I:",
255a264,269
> 		case 'w':
> 			word_delay = atoi(optarg);
> 			break;
> 		case 'P':
> 			pause_us = atoi(optarg);
> 			break;
403c417
< static void transfer_buf(int fd, int len)
---
> static void transfer_buf(int fd, int len, uint8_t *tx_buf, uint8_t *rx_buf)
409,413c423,431
< 	tx = malloc(len);
< 	if (!tx)
< 		pabort("can't allocate tx buffer");
< 	for (i = 0; i < len; i++)
< 		tx[i] = random();
---
> 	if (tx_buf)
> 		tx = tx_buf;
> 	else {
> 		tx = malloc(len);
> 		if (!tx)
> 			pabort("can't allocate tx buffer");
> 		for (i = 0; i < len; i++)
> 			tx[i] = random();
> 	}
415,417c433,439
< 	rx = malloc(len);
< 	if (!rx)
< 		pabort("can't allocate rx buffer");
---
> 	if (rx_buf)
> 		rx = rx_buf;
> 	else {
> 		rx = malloc(len);
> 		if (!rx)
> 			pabort("can't allocate rx buffer");
> 	}
418a441,448
> 	if (tx_buf) {
> 		char mp[5];
> 		if (len >= sizeof mp - 1) {
> 			snprintf(mp, sizeof mp, "%04d", iterations % 1000);
> 			memcpy(tx_buf + len - 4, mp, sizeof mp - 1);
> 		}
> 	}
> 	
433,434c463,466
< 	free(rx);
< 	free(tx);
---
> 	if (!rx_buf)
> 		free(rx);
> 	if (!tx_buf)
> 		free(tx);
497a530,532
> 	printf("delay: %u usecs\n", delay);
> 	printf("word_delay: %u usecs\n", word_delay);
> 	printf("pause: %u usecs\n", pause_us);
505c540,542
< 
---
> 		uint8_t *tx_buf = 0;
> 		uint8_t *rx_buf = 0;
> 		
507a545,557
> 		if (iterations) {
> 			int i;
> 			
> 			rx_buf = malloc(transfer_size);
> 			assert(rx_buf);
> 			tx_buf = malloc(transfer_size);
> 			assert(tx_buf);
> 
> 			for (i = 0; i < transfer_size; i++) {
> 				tx_buf[i] = '0' + (i % 10);
> 			}
> 		}
> 		
511c561
< 			transfer_buf(fd, transfer_size);
---
> 			transfer_buf(fd, transfer_size, tx_buf, rx_buf);
517a568,570
> 
> 			if (pause_us)
> 				usleep(pause_us);
520a574,578
> 
> 		if (tx_buf)
> 			free(tx_buf);
> 		if (rx_buf)
> 			free(rx_buf);
$