libpayload/keyboard: Revise keyboard_cmd() error handling

Even if we are careful, it's still possible that we read spurious
data from the keyboard, e.g. keystrokes. Namely, when we send the
reset/disable command, there is a race before the command is pro-
cessed.

So we should always process data from the keyboard in a loop. We
break it, when an ACK (0xfa) or a NAK (0xfe) is received, and warn
on unexpected data unless it might be due to the mentioned race.

This also gives us the opportunity to use command-specific timeouts
which we take from Linux: 1s for the keyboard self-test (as there
are keyboards that perform the test before acking the command) and
200ms for all other commands.

Change-Id: I60a2643a8ff4b9231c63bf970c8749c97c7d8926
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/47083
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>

0 files changed, 0 insertions, 0 deletions