ao-tools: Wait for device to become ready instead of failing

For some reason, USB devices take 'a while' to become usable; instead
of bailing immediately, sit around waiting to see if the device
becomes usable if we get an EBUSY or EACCES error.

Signed-off-by: Keith Packard <keithp@keithp.com>

1 files changed, 18 insertions, 2 deletions

diff --git a/ao-tools/lib/cc-usb.c b/ao-tools/lib/cc-usb.c
index d7ac138c..a3a19d5c 100644
--- a/ao-tools/lib/cc-usb.c
+++ b/ao-tools/lib/cc-usb.c
@@ -412,19 +412,35 @@ cc_usb_close_remote(struct cc_usb *cc)
 
 static struct termios	save_termios;
 
+#include <errno.h>
+
 struct cc_usb *
 cc_usb_open(char *tty)
 {
 	struct cc_usb	*cc;
 	struct termios	termios;
+	int		i;
 
 	if (!tty)
 		tty = DEFAULT_TTY;
 	cc = calloc (sizeof (struct cc_usb), 1);
 	if (!cc)
 		return NULL;
-	cc->fd = open(tty, O_RDWR | O_NONBLOCK);
-	if (cc->fd < 0) {
+	i = 0;
+	for (;;) {
+		cc->fd = open(tty, O_RDWR | O_NONBLOCK);
+		if (cc->fd >= 0)
+			break;
+		i++;
+		if (errno == EBUSY || errno == EPERM || errno == EACCES) {
+			fprintf(stderr, "open failed, pausing");
+			perror(tty);
+			if (i < 20) {
+				sleep(3);
+				continue;
+			}
+		}
+
 		perror(tty);
 		free (cc);
 		return NULL;