From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Michael Bideau <[email protected]>
Date: Wed, 2 Oct 2019 23:48:10 +0200
Subject: [PATCH] at_keyboard: Fix unreliable key presses

This patch fixes an issue that prevented the at_keyboard module to work
(for me). The cause was a bad/wrong return value in the
grub_at_keyboard_getkey() function in grub-core/term/at_keyboard.c file
at line 237. My symptoms were to have an unresponsive keyboard. Keys
needed to be pressed 10x and more to effectively be printed sometimes
generating multiple key presses (after 1 or 2 sec of no printing). It
was very problematic when typing passphrase in early stage (with
GRUB_ENABLE_CRYPTODISK). When switched to "console" terminal input
keyboard worked perfectly. It also worked great with the GRUB 2.02
packaged by Debian (2.02+dfsg1-20). It was not an output issue but an
input one.

I've managed to analyze the issue and found that it came from the commit
216950a4e (at_keyboard: Split protocol from controller code.). Three
lines where moved from the fetch_key() function in
grub-core/term/at_keyboard.c file to the beginning of
grub_at_keyboard_getkey() function (same file). However, returning -1
made sense when it happened in fetch_key() function but not anymore in
grub_at_keyboard_getkey() function which should return GRUB_TERM_NO_KEY.
I think it was just an incomplete cut-paste missing a small manual
correction. Let's fix it.

Note: Commit message updated by Daniel Kiper.

Signed-off-by: Michael Bideau <[email protected]>
Reviewed-by: Daniel Kiper <[email protected]>
(cherry picked from commit 33203ca3484717712b54e199c46ae8a818374284)
---
 grub-core/term/at_keyboard.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/grub-core/term/at_keyboard.c b/grub-core/term/at_keyboard.c
index c805cccbd..dac0f946f 100644
--- a/grub-core/term/at_keyboard.c
+++ b/grub-core/term/at_keyboard.c
@@ -318,7 +318,7 @@ grub_at_keyboard_getkey (struct grub_term_input *term __attribute__ ((unused)))
     return GRUB_TERM_NO_KEY;
 
   if (! KEYBOARD_ISREADY (grub_inb (KEYBOARD_REG_STATUS)))
-    return -1;
+    return GRUB_TERM_NO_KEY;
   at_key = grub_inb (KEYBOARD_REG_DATA);
   old_led = ps2_state.led_status;