Messages in this thread | | | Date | Tue, 29 Jul 2003 20:29:01 +0200 (MET DST) | From | "Maciej W. Rozycki" <> | Subject | Re: i8042 problem |
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On Mon, 28 Jul 2003, Andries Brouwer wrote:
> > > > Well, are timeouts needed at all? > > > > > > Yes. We send a command to the keyboard. It may react, or it may not. > > > > But we need not wait for that actively. If we are unsure about a result > > of a command, then we may send a command in question followed with an echo > > request. This assures an IRQ will finally arrive and if no command > > response arrives before an echo response, then the keyboard ignored the > > command. I used this approach many years ago to differ between PS/2 > > keyboards (which respond with 0xfa,0xab,0x83 to a request for ID) and > > genuine PC/AT ones (which respond with lone 0xfa). It worked. > > And what did you do for XT? :-)
Nice joke, but I'll answer seriously. No support was provided. Hooking a PC/XT keyboard to the 8042, if supported, requires a different setup of the command byte and is possibly done by the system firmware. You can read the command byte to see which configuration is used.
Wrt polling vs IRQ-driven probing and setup: using IRQ is a natural choice as you have to do keyboard detection in the IRQ handler anyway to properly support hot plugging of a PC/AT or a PS/2 keyboard.
-- + Maciej W. Rozycki, Technical University of Gdansk, Poland + +--------------------------------------------------------------+ + e-mail: macro@ds2.pg.gda.pl, PGP key available +
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