Avoid draining the keyboard buffer during gateA20_set(). It shouldn't

[people/xl0/gpxe.git] / src / arch / i386 / firmware / pcbios / gateA20.c

diff --git a/src/arch/i386/firmware/pcbios/gateA20.c b/src/arch/i386/firmware/pcbios/gateA20.c
index 5a27e70..cdc8668 100644 (file)
--- a/src/arch/i386/firmware/pcbios/gateA20.c
+++ b/src/arch/i386/firmware/pcbios/gateA20.c
@@ -27,16 +27,17 @@ enum { Disable_A20 = 0x2400, Enable_A20 = 0x2401, Query_A20_Status = 0x2402,
 #define CF ( 1 << 0 )
 
 #ifndef IBM_L40
-static void empty_8042 ( void )
-{
+static void empty_8042 ( void ) {
        unsigned long time;
-       char st;
 
        time = currticks() + TICKS_PER_SEC;     /* max wait of 1 second */
-       while ((((st = inb(K_CMD)) & K_OBUF_FUL) ||
-              (st & K_IBUF_FUL)) &&
-              currticks() < time)
-               inb(K_RDWR);
+       while ( ( inb ( K_CMD ) & K_IBUF_FUL ) &&
+               currticks() < time ) {
+               /* Do nothing.  In particular, do *not* read from
+                * K_RDWR, because that will drain the keyboard buffer
+                * and lose keypresses.
+                */
+       }
 }
 #endif /* IBM_L40 */
 
@@ -66,6 +67,7 @@ void gateA20_set ( void ) {
                               : "=r" ( flags ), "=a" ( discard_a )
                               : "a" ( Enable_A20 ) );
 
+
        if ( flags & CF ) {
                /* INT 15 method failed, try alternatives */
 #ifdef IBM_L40
@@ -78,7 +80,7 @@ void gateA20_set ( void ) {
                empty_8042();
 #endif /* IBM_L40 */
        }
-       
+
        reentry_guard = 0;
 }