[bug report] tools: iio: iio_generic_buffer: allow continuous looping

[Dan Carpenter <dan.carpenter@oracle.com>]

Hello Martin Kelly,

The patch 55dda0abcf9d: "tools: iio: iio_generic_buffer: allow
continuous looping" from May 17, 2018, leads to the following static
checker warning:

	./tools/iio/iio_generic_buffer.c:640 main()
	warn: unsigned 'num_loops' is never less than zero.

./tools/iio/iio_generic_buffer.c
    331 int main(int argc, char **argv)
    332 {
    333 	unsigned long long num_loops = 2;
                ^^^^^^^^

    334 	unsigned long timedelay = 1000000;
    335 	unsigned long buf_len = 128;
    336 
    337 	ssize_t i;
    338 	unsigned long long j;
    339 	unsigned long toread;
    340 	int ret, c;
    341 	int fp = -1;
    342 
    343 	int num_channels = 0;
    344 	char *trigger_name = NULL, *device_name = NULL;
    345 
    346 	char *data = NULL;
    347 	ssize_t read_size;
    348 	int dev_num = -1, trig_num = -1;
    349 	char *buffer_access = NULL;
    350 	int scan_size;
    351 	int noevents = 0;
    352 	int notrigger = 0;
    353 	char *dummy;
    354 	bool force_autochannels = false;
    355 
    356 	struct iio_channel_info *channels = NULL;
    357 

[ snip ]

    632 	/* Attempt to open non blocking the access dev */
    633 	fp = open(buffer_access, O_RDONLY | O_NONBLOCK);
    634 	if (fp == -1) { /* TODO: If it isn't there make the node */
    635 		ret = -errno;
    636 		fprintf(stderr, "Failed to open %s\n", buffer_access);
    637 		goto error;
    638 	}
    639 
--> 640 	for (j = 0; j < num_loops || num_loops < 0; j++) {
                                             ^^^^^^^^^^^^^
If num_loops is -1 then it's supposed to loop forever.  It basically
does, except for the static checker warning.

    641 		if (!noevents) {
    642 			struct pollfd pfd = {
    643 				.fd = fp,
    644 				.events = POLLIN,
    645 			};
    646 
    647 			ret = poll(&pfd, 1, -1);
    648 			if (ret < 0) {
    649 				ret = -errno;
    650 				goto error;
    651 			} else if (ret == 0) {
    652 				continue;
    653 			}
    654 
    655 			toread = buf_len;
    656 		} else {
    657 			usleep(timedelay);
    658 			toread = 64;
    659 		}

regards,
dan carpenter