altos: Make stdio 8-bit clean by making pollchar return int

We were stealing one value (0xff) in the return value from pollchar to
indicate 'not ready yet'. Instead of doing that, use the integer value
-1 and have pollchar return an int instead of a char. That
necessitated cleaning a few other bits to make sure that 0xff wouldn't
get promoted to -1 on accident.

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

1 files changed, 1 insertions, 1 deletions

diff --git a/src/core/ao_usb.h b/src/core/ao_usb.h
index e051db93..4476ee6b 100644
--- a/src/core/ao_usb.h
+++ b/src/core/ao_usb.h
@@ -33,7 +33,7 @@ ao_usb_getchar(void);
 /* Poll for a charcter on the USB input queue.
  * returns AO_READ_AGAIN if none are available
  */
-char
+int
 ao_usb_pollchar(void);
 
 /* Flush the USB output queue */