From: dingbat@diku.dk (Niels Skov Olsen)

Here is the real fix to the trouble I and others have had
with keyboard lockups and LED malfunction. I think this
should be included in the next release, but I don't know 
the proper procedure for doing so. I post it here because
others have reported the same or similar problem.

The problem was that the keyboard would lock up when pressing
either of CAPS, NUMLOCK, SCROLL LOCK. The 'bug' shows up only
on some hardware. The fix as suggested by Bruce Evans was to
add a routine called kb_ack that waits until 0xfa shows up on
port 0x64, and call after outputting data to port 0x60. I am not
sure what the exact meaning of these ports are, but the patch
that follows fixes the lockups and makes the LED's work!

Thank you Bruce Evans.

Niels

Apply this patch in kernel/chr_drv/ :

*** /tmp/linux/kernel/chr_drv/keyboard.S        Thu Apr  9 22:15:22 1992
--- keyboard.S  Tue Apr 21 19:49:33 1992
***************
*** 182,194 ****
--- 182,196 ----
        je 1f
        movb %al,old_leds
        call kb_wait
        movb $0xed,%al          /* set leds command */
        outb %al,$0x60
+       call kb_ack             /* [NSO]: Suggested by Bruce Evans */
        call kb_wait
        movb _kleds,%al
        outb %al,$0x60
+       call kb_ack             /* [NSO]: Suggested by Bruce Evans */
  1:    ret
  uncaps:       andb $0x7f,_kmode
        ret
  scroll:
        testb $0x03,_kmode
***************
*** 782,791 ****
--- 784,817 ----
        pushl %eax
        pushl %ebx
        movl $10000,%ebx
  1:    inb $0x64,%al
        testb $0x02,%al
+       je 2f
+       decl %ebx
+       jne 1b
+ 2:    popl %ebx
+       popl %eax
+       ret
+ 
+ /*
+  * kb_ack waits for 0xfa to appear in port 0x60
+  *
+  * Suggested by Bruce Evans
+  * Added by Niels Skou Olsen [NSO]
+  * April 21, 1992
+  *
+  * Heavily inspired by kb_wait :-)
+  * I dont know how much waiting actually is required, 
+  * but this seems to work.
+  */
+ kb_ack:
+       pushl %eax
+       pushl %ebx
+       movl $10000,%ebx
+ 1:    inb $0x60,%al
+       testb $0xfa,%al
        je 2f
        decl %ebx
        jne 1b
  2:    popl %ebx
        popl %eax