From 99716520d4cf093d42f5a93cac73964ceffc6b4e Mon Sep 17 00:00:00 2001
From: Ain <41307858+nero@users.noreply.github.com>
Date: Mon, 13 Aug 2018 12:16:35 +0200
Subject: [PATCH 5/5] Reuse kernel-side configuration for console= devices

Instead of parsing the console= options in the initramfs, we ask the
kernel of its interpretation of the console= parameters. The kernel
does the console setup as part of its early startup, including the
configuration of the baud rate, control bits and flow control.

The options and format of the console= parameter are documented here:
https://www.kernel.org/doc/html/v4.15/admin-guide/serial-console.html

By keeping the settings from the kernel, we avoid baud rate switching
between printk and getty output on edge cases.

This adds support for additional tty types, like hvc, while removing
string parsing code from the initramfs.
---
 initramfs-init.in | 44 +++++++++++++++++---------------------------
 1 file changed, 17 insertions(+), 27 deletions(-)

diff --git a/initramfs-init.in b/initramfs-init.in
index 1d0f079..020f13c 100755
--- a/initramfs-init.in
+++ b/initramfs-init.in
@@ -105,34 +105,28 @@ rc_add() {
 	ln -sf /etc/init.d/$1 $sysroot/etc/runlevels/$2/$1
 }
 
-setup_inittab_console(){
-	while [ $# -gt 0 ]; do
-		local tty=${1%,*}
-		local speed=${1#*,}
-		local line=
-		local term=
-		case "$tty" in
-			ttyS*|ttyMFD*|ttyUSB*|ttyAMA*)
-				term=vt100
-				line=-L
-				flow=${speed##*[^r]}
-				speed=${speed%%[^0-9]*}
-				speed=${speed:-115200}
-				;;
-			*)
-				[ "$speed" = "$1" ] && speed=38400
-				;;
-		esac
-		shift
+# Recursively resolve tty aliases like console or tty0
+list_console_devices() {
+	if ! [ -e /sys/class/tty/$1/active ]; then
+		echo $1
+		return
+	fi
 
-		# skip "current console" from being added to inittab
-		[ "$tty" = "tty0" ] && continue
+	for dev in $(cat /sys/class/tty/$1/active); do
+		list_console_devices $dev
+	done
+}
 
+setup_inittab_console(){
+	term=vt100
+	# Inquire the kernel for list of console= devices
+	for tty in $(list_console_devices console); do
 		# do nothing if inittab already have the tty set up
 		if ! grep -q "^$tty:" $sysroot/etc/inittab; then
 			echo "# enable login on alternative console" \
 				>> $sysroot/etc/inittab
-			echo "$tty::respawn:/sbin/getty ${flow:+-h }$line $speed $tty $term" \
+			# Baudrate of 0 keeps settings from kernel
+			echo "$tty::respawn:/sbin/getty -L 0 $tty $term" \
 				>> $sysroot/etc/inittab
 		fi
 		if [ -e "$sysroot"/etc/securetty ] && ! grep -q -w "$tty" "$sysroot"/etc/securetty; then
@@ -302,10 +296,6 @@ for opt; do
 		SINGLEMODE=yes
 		continue
 		;;
-	console=*)
-		CONSOLE="$CONSOLE ${opt#console=}"
-		continue
-		;;
 	esac
 
 	for i in $myopts; do
@@ -731,7 +721,7 @@ if [ -f "$sysroot"/etc/fstab ]; then
 fi
 
 # fix inittab if alternative console
-setup_inittab_console $CONSOLE
+setup_inittab_console
 
 # copy alpine release info
 #if ! [ -f "$sysroot"/etc/alpine-release ] && [ -f $ALPINE_MNT/.alpine-release ]; then
-- 
2.18.0