BUG: pc_keyb.c

From [email protected] Tue Aug 21 00:48:32 2001

> But the present code does not guarantee such a delay at all. > For example, kbd_write_cmd() does
> kb_wait();
> outb(...);
> kb_wait();
> where the second kb_wait reads the status very quickly after the first.

Thats wrong by the spec. I dug out my docs - there is a required 1mS (not 2 tho) delay for keyboard port accesses.

Since there are various keyboard and mouse paths that can lead to register access, it seems that we must either prefix each access by a wait, or otherwise we must remember at what time we last did a read.

Something else is that on some ancient (MCA) systems a delay is required between finding the ready bit and actually reading the data (Frank van Gilluwe, p. 273: wait 7 us).

On the other hand, 1 ms is a very long time these days; it is a bit surprising that modern hardware should need delays in that order of magnitude; maybe the problem is elsewhere and the mdelay(2) happens to change the timing and avoid the problem.