From: Keith Packard <keithp@keithp.com>
Date: Thu, 5 Nov 2009 05:32:07 +0000 (-0800)
Subject: In USB pollchar, wait for packet before re-checking USB out len
X-Git-Tag: debian/0.6+27+gb0d7e3f~17
X-Git-Url: https://git.gag.com/?p=fw%2Faltos;a=commitdiff_plain;h=3ece984f4d72b4f720a5efdfaad7cff77a93d676

In USB pollchar, wait for packet before re-checking USB out len

This probably wouldn't actually cause a problem, but it seems more
reliable to wait for a packet interrupt before re-reading the packet
OUT len register. This could avoid spinning while waiting for a USB
packet, which seems like a good thing.

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

diff --git a/src/ao_usb.c b/src/ao_usb.c
index daca71a7..527e9b30 100644
--- a/src/ao_usb.c
+++ b/src/ao_usb.c
@@ -377,11 +377,13 @@ char
 ao_usb_pollchar(void) __critical
 {
 	char c;
-	while (ao_usb_out_bytes == 0) {
+	if (ao_usb_out_bytes == 0) {
 		USBINDEX = AO_USB_OUT_EP;
 		if ((USBCSOL & USBCSOL_OUTPKT_RDY) == 0)
 			return AO_READ_AGAIN;
 		ao_usb_out_bytes = (USBCNTH << 8) | USBCNTL;
+		if (ao_usb_out_bytes == 0)
+			return AO_READ_AGAIN;
 	}
 	--ao_usb_out_bytes;
 	c = USBFIFO[AO_USB_OUT_EP << 1];