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vt: add fallback to plain map for modifier-aware key types

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When a key is pressed with modifiers (Shift, Ctrl, Alt, etc.) and the
modifier-specific keymap has no binding (K_HOLE) or doesn't exist, fall
back to the plain keymap if the plain entry is a modifier-aware type
(KT_CUR or KT_CSI).

This allows arrow keys and CSI navigation keys to automatically handle
all modifier combinations with just a single plain map entry. The key
handlers (k_cur and k_csi) read the modifier state at runtime and encode
it into the output sequence.

For example, with just:
    keycode 103 = Up
    keycode 104 = Csi_Home

All these combinations now work automatically:
    Up         -> ESC [ A
    Shift+Up   -> ESC [ 1 ; 2 A
    Ctrl+Up    -> ESC [ 1 ; 5 A
    Home       -> ESC [ 1 ~
    Shift+Home -> ESC [ 1 ; 2 ~
    Ctrl+Home  -> ESC [ 1 ; 5 ~

Previously, each modifier combination required an explicit keymap entry,
which was tedious and consumed keymap slots.

Explicit modifier bindings still take precedence - the fallback only
triggers when the modifier-specific entry is empty.

Signed-off-by: Nicolas Pitre <npitre@baylibre.com>
Link: https://patch.msgid.link/20260203045457.1049793-4-nico@fluxnic.net
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Nicolas Pitre
2026-02-02 23:52:48 -05:00
committed by Greg Kroah-Hartman
parent 5cba06c71c
commit c1d2deb649
1 changed files with 15 additions and 0 deletions
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15
drivers/tty/vt/keyboard.c
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@@ -1498,6 +1498,21 @@ static void kbd_keycode(unsigned int keycode, int down, bool hw_raw)
param.ledstate = kbd->ledflagstate;
key_map = key_maps[shift_final];
/*
* Fall back to the plain map if modifiers are active, the modifier-
* specific map is missing or has no entry, and the plain map has a
* modifier-aware key type (KT_CUR or KT_CSI). These handlers encode
* the modifier state into the emitted escape sequence.
*/
if (shift_final && keycode < NR_KEYS &&
(!key_map || key_map[keycode] == K_HOLE) && key_maps[0]) {
unsigned short plain = key_maps[0][keycode];
unsigned char type = KTYP(plain);
if (type >= 0xf0 && (type - 0xf0 == KT_CUR || type - 0xf0 == KT_CSI))
key_map = key_maps[0];
}
rc = atomic_notifier_call_chain(&keyboard_notifier_list,
KBD_KEYCODE, &param);
if (rc == NOTIFY_STOP || !key_map) {