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, 10 insertions, 14 deletions

diff --git a/src/stm/ao_serial_stm.c b/src/stm/ao_serial_stm.c
index 00409f4a..94138edc 100644
--- a/src/stm/ao_serial_stm.c
+++ b/src/stm/ao_serial_stm.c
@@ -17,13 +17,6 @@
 
 #include <ao.h>
 
-struct ao_stm_usart {
-	struct ao_fifo		rx_fifo;
-	struct ao_fifo		tx_fifo;
-	struct stm_usart	*reg;
-	uint8_t			tx_started;
-};
-
 void
 ao_debug_out(char c)
 {
@@ -78,16 +71,19 @@ ao_usart_getchar(struct ao_stm_usart *usart)
 	return c;
 }
 
-char
+int
 ao_usart_pollchar(struct ao_stm_usart *usart)
 {
-	char	c;
+	int	c;
 	
 	ao_arch_block_interrupts();
 	if (ao_fifo_empty(usart->rx_fifo))
 		c = AO_READ_AGAIN;
-	else
-		ao_fifo_remove(usart->rx_fifo,c);
+	else {
+		uint8_t	u;
+		ao_fifo_remove(usart->rx_fifo,u);
+		c = u;
+	}
 	ao_arch_release_interrupts();
 	return c;
 }
@@ -201,7 +197,7 @@ ao_serial1_putchar(char c)
 	ao_usart_putchar(&ao_stm_usart1, c);
 }
 
-char
+int
 ao_serial1_pollchar(void)
 {
 	return ao_usart_pollchar(&ao_stm_usart1);
@@ -232,7 +228,7 @@ ao_serial2_putchar(char c)
 	ao_usart_putchar(&ao_stm_usart2, c);
 }
 
-char
+int
 ao_serial2_pollchar(void)
 {
 	return ao_usart_pollchar(&ao_stm_usart2);
@@ -263,7 +259,7 @@ ao_serial3_putchar(char c)
 	ao_usart_putchar(&ao_stm_usart3, c);
 }
 
-char
+int
 ao_serial3_pollchar(void)
 {
 	return ao_usart_pollchar(&ao_stm_usart3);