vt: add KT_CSI keysym type for modifier-aware CSI sequences

Add a new keysym type KT_CSI that generates CSI tilde sequences with
automatic modifier encoding. The keysym value encodes the CSI parameter
number, producing sequences like ESC [ <value> ~ or ESC [ <value> ; <mod> ~
when Shift, Alt, or Ctrl modifiers are held.

This allows navigation keys (Home, End, Insert, Delete, PgUp, PgDn) and
function keys to generate modifier-aware escape sequences without
consuming string table entries for each modifier combination.

Define key symbols for navigation keys (K_CSI_HOME, K_CSI_END, etc.)
and function keys (K_CSI_F1 through K_CSI_F20) using standard xterm
CSI parameter values.

The modifier encoding follows the xterm convention:
  mod = 1 + (shift ? 1 : 0) + (alt ? 2 : 0) + (ctrl ? 4 : 0)

Allowed CSI parameter values range from 0 to 99.

Note: The Linux console historically uses a non-standard double-bracket
format for F1-F5 (ESC [ [ A through ESC [ [ E) rather than the xterm
tilde format (ESC [ 11 ~ through ESC [ 15 ~). The K_CSI_F1 through
K_CSI_F5 definitions use the xterm format. Converting F1-F5 to KT_CSI
would require updating the "linux" terminfo entry to match. Navigation
keys and F6-F20 already use the tilde format and are fully compatible.

Signed-off-by: Nicolas Pitre <npitre@baylibre.com>
Link: https://patch.msgid.link/20260203045457.1049793-3-nico@fluxnic.net
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 33 insertions, 5 deletions

diff --git a/drivers/tty/vt/keyboard.c b/drivers/tty/vt/keyboard.c
index cb907a3b9d3d..44fd67eb723a 100644
--- a/drivers/tty/vt/keyboard.c
+++ b/drivers/tty/vt/keyboard.c
@@ -74,7 +74,7 @@ static inline int kbd_defleds(void)
 	k_self,		k_fn,		k_spec,		k_pad,\
 	k_dead,		k_cons,		k_cur,		k_shift,\
 	k_meta,		k_ascii,	k_lock,		k_lowercase,\
-	k_slock,	k_dead2,	k_brl,		k_ignore
+	k_slock,	k_dead2,	k_brl,		k_csi
 
 typedef void (k_handler_fn)(struct vc_data *vc, unsigned char value,
 			    char up_flag);
@@ -127,6 +127,7 @@ static const unsigned char max_vals[] = {
 	[ KT_SLOCK	] = NR_LOCK - 1,
 	[ KT_DEAD2	] = 255,
 	[ KT_BRL	] = NR_BRL - 1,
+	[ KT_CSI	] = 99,
 };
 
 static const int NR_TYPES = ARRAY_SIZE(max_vals);
@@ -644,10 +645,6 @@ static void fn_null(struct vc_data *vc)
 /*
  * Special key handlers
  */
-static void k_ignore(struct vc_data *vc, unsigned char value, char up_flag)
-{
-}
-
 static void k_spec(struct vc_data *vc, unsigned char value, char up_flag)
 {
 	if (up_flag)
@@ -1029,6 +1026,37 @@ static void k_brl(struct vc_data *vc, unsigned char value, char up_flag)
 	}
 }
 
+/*
+ * Handle KT_CSI keysym type: generate CSI tilde sequences with modifier
+ * support. The value encodes the CSI parameter number, producing sequences
+ * like ESC [ <value> ~ or ESC [ <value> ; <mod> ~ when modifiers are held.
+ */
+static void k_csi(struct vc_data *vc, unsigned char value, char up_flag)
+{
+	char buf[10];
+	int i = 0;
+	int mod;
+
+	if (up_flag)
+		return;
+
+	mod = csi_modifier_param();
+
+	buf[i++] = 0x1b;
+	buf[i++] = '[';
+	if (value >= 10)
+		buf[i++] = '0' + value / 10;
+	buf[i++] = '0' + value % 10;
+	if (mod > 1) {
+		buf[i++] = ';';
+		buf[i++] = '0' + mod;
+	}
+	buf[i++] = '~';
+	buf[i] = 0x00;
+
+	puts_queue(vc, buf);
+}
+
 #if IS_ENABLED(CONFIG_INPUT_LEDS) && IS_ENABLED(CONFIG_LEDS_TRIGGERS)
 
 struct kbd_led_trigger {