Workaround Icarus UART failures by reopening the tty every scanhash

ngzhang says the USB-UART chip isn't stable on some computers, and I'm experiencing some weirdness myself.
This workaround seems to fix it (tested for over 48 hours, whereas failure is usually in well under 5 hours).

icarus.c

@@ -225,15 +225,6 @@ static bool icarus_prepare(struct thr_info *thr)
 
 	struct timeval now;
 
-	int fd = icarus_open(icarus->device_path);
-	if (unlikely(-1 == fd)) {
-		applog(LOG_ERR, "Failed to open Icarus on %s",
-		       icarus->device_path);
-		return false;
-	}
-
-	icarus->device_fd = fd;
-
 	applog(LOG_INFO, "Opened Icarus on %s", icarus->device_path);
 	gettimeofday(&now, NULL);
 	get_datestamp(icarus->init, &now);
@@ -255,7 +246,13 @@ static uint64_t icarus_scanhash(struct thr_info *thr, struct work *work,
 	time_t t = 0;
 
 	icarus = thr->cgpu;
-	fd = icarus->device_fd;
+
+	fd = icarus_open(icarus->device_path);
+	if (unlikely(-1 == fd)) {
+		applog(LOG_ERR, "Failed to open Icarus on %s",
+		       icarus->device_path);
+		return 0;
+	}
 
 	memset(ob_bin, 0, sizeof(ob_bin));
 	memcpy(ob_bin, work->midstate, 32);
@@ -266,8 +263,10 @@ static uint64_t icarus_scanhash(struct thr_info *thr, struct work *work,
 	tcflush(fd, TCOFLUSH);
 #endif
 	ret = icarus_write(fd, ob_bin, sizeof(ob_bin));
-	if (ret)
+	if (ret) {
+		icarus_close(fd);
 		return 0;	/* This should never happen */
+	}
 
 	ob_hex = bin2hex(ob_bin, sizeof(ob_bin));
 	if (ob_hex) {
@@ -291,8 +290,10 @@ static uint64_t icarus_scanhash(struct thr_info *thr, struct work *work,
 
 	memcpy((char *)&nonce, nonce_bin, sizeof(nonce_bin));
 
-        if (nonce == 0 && ret)
+	if (nonce == 0 && ret) {
+		icarus_close(fd);
                 return 0xffffffff;
+	}
 
 #ifndef __BIG_ENDIAN__
 	nonce = swab32(nonce);
@@ -310,6 +311,7 @@ static uint64_t icarus_scanhash(struct thr_info *thr, struct work *work,
                         hash_count <<= 1;
         }
 
+	icarus_close(fd);
         return hash_count;
 }
 
@@ -323,8 +325,6 @@ static void icarus_shutdown(struct thr_info *thr)
 		if (icarus->device_path)
 			free(icarus->device_path);
 
-		close(icarus->device_fd);
-
 		devices[icarus->device_id] = NULL;
 		free(icarus);