[mubios] Initialize the 8042 keyboard controller

POST only unmasked IRQ1 in the PIC and never configured the 8042 itself, so
the keyboard stayed in its post-reset disabled state: the clock was inhibited
and no scan code ever reached the output buffer. IRQ1 never fired, the BDA
keyboard buffer stayed empty, and GRUB polling INT 16h AH=01h never saw a key.

Add kbd_init() to disable both ports, drain the output buffer, clear the clock
inhibit bits in the command byte, enable the keyboard and auxiliary IRQs and
select set 1 translation, then enable scanning with 0xF4.

The IRQ1 handler now checks the status register for a pending output byte
before reading the data port and drops auxiliary port bytes. The set 2 break
prefix tracking is gone because translation is enabled.

1 files changed, 2 insertions, 13 deletions

diff --git a/mubios/services/int16.c b/mubios/services/int16.c
index 5872fb1..cadc1ff 100644
--- a/mubios/services/int16.c
+++ b/mubios/services/int16.c
@@ -17,6 +17,7 @@
  */
 
 #include "bios.h"
+#include "io.h"
 #include "regs.h"
 
 #define BIOS_ZF 0x0040u
@@ -27,18 +28,6 @@
 #define BDA_KBD_BUFFER_END 0x003Eu
 
 static u8
-normalize_scancode (u8 scancode)
-{
-  switch (scancode)
-    {
-    case 0x5Au:
-      return 0x1Cu;
-    default:
-      return scancode;
-    }
-}
-
-static u8
 scancode_to_ascii (u8 scancode)
 {
   switch (scancode)
@@ -138,7 +127,7 @@ int16_service (struct bios_regs *regs)
 
   position = *head;
   value = buffer[(position - BDA_KBD_BUFFER_START) >> 1];
-  scancode = normalize_scancode ((u8)(value >> 8));
+  scancode = (u8)(value >> 8);
   ascii = scancode_to_ascii (scancode);
 
   regs->eax = ((u32)scancode << 8) | ascii;