On Sun, Jul 14, 2002 at 02:17:31PM +0200, Andries Brouwer wrote:
> On Sun, Jul 14, 2002 at 02:01:53PM +0200, Vojtech Pavlik wrote:
>
> > > mice: PS/2 mouse device common for all mice
> > > atkbd.c: Sent: f5
> > > atkbd.c: Received fe
> > > serio: i8042 KBD port at 0x60,0x64 irq 1
> >
> > Ok. So this is the cause. The driver gets a '0xfe' response, which means
> > "error, command not supported, or device not present'.
> >
> > A keyboard must support the 0xf5 command ('reset').
>
> I have not followed the discussion and probably say something
> entirely out of context. But from the good old days I seem to
> recall commands 0xff "reset", 0xf5 "set defaults and deactivate"
> and reply 0xfe "please resend".
>
> In principle nothing is wrong when one gets a 0xfe.
> The request is just: please say that again.
Commands:
0xf5 - n/a - Keyboard
Reset and disable keyboard. The keyboard performs a reset to a power
on state (without affecting the LEDs) and stops generating events.
0xff - 1*R - Keyboard / Mouse
Reset and perform the Basic Assurance Test (BAT). Device returns a
BAT completion code 0xaa. If it's a keyboard, then switches to scancode
set 2. If it's a mouse, it also sends 0x00, 0x03 or 0x04 after 0xaa.
Since BAT is also triggered on power-on, a device will send 0xaa
immediately after being plugged in.
Responses:
0xfe
Resend. Keyboard will send this if it didn't receive the last command
correctly.
Unfortunately, 0xfe also happens when you send a command to a keyboard
that's not plugged, or when the keyboard doesn't understand the command.
Resending in those cases (which are the most common) would cause an
infinite loop ...
-- Vojtech Pavlik SuSE Labs - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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