sysvinit-inittab/start_getty: Check /sys for the tty device existence

The hvc tty driver doesn't populate a file like /proc/tty/driver/serial,
so the current implementation of start_getty doesn't work for the hvc
console. By checking the /sys/class/tty/ for the tty device existence,
it should support more console types and also make the codes more simple.

(From OE-Core rev: 670ceef0f6584ece5ce4176610255226a6148570)

Signed-off-by: Kevin Hao <kexin.hao@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-core/sysvinit/sysvinit-inittab/start_getty

@@ -1,17 +1,4 @@
 #!/bin/sh
-###############################################################################
-# This script is used to automatically set up the serial console(s) on startup.
-# The variable SERIAL_CONSOLES can be set in meta/conf/machine/*.conf.
-# Script enhancement has been done based on Bug YOCTO #10844.
-# Most of the information is retrieved from /proc virtual filesystem containing
-# all the runtime system information (eg. system memory, device mount, etc).
-###############################################################################
-
-# Get active serial filename.
-active_serial=$(grep "serial" /proc/tty/drivers | cut -d/ -f1 | sed "s/ *$//")
-
-# Rephrase input parameter from ttyS target index (ttyS1, ttyS2, ttyAMA0, etc).
-runtime_tty=$(echo $2 | grep -oh '[0-9]\+')
 
 # busybox' getty does this itself, util-linux' agetty needs extra help
 getty="/sbin/getty"
@@ -25,31 +12,6 @@ case $(readlink -f "${getty}") in
         ;;
 esac
 
-# Backup $IFS.
+if [ -e /sys/class/tty/$2 -a -c /dev/$2 ]; then
-DEFAULT_IFS=$IFS
+	${setsid:-} ${getty} -L $1 $2 $3
-# Customize Internal Field Separator.
+fi
-IFS="$(printf '\n\t')"
-
-for line in $active_serial; do
-	# Check we have the file containing current active serial target index.
-	if [ -e "/proc/tty/driver/$line" ]
-        then
-		# Remove all unknown entries and discard the first line (desc).
-		activetty=$(grep -v "unknown" "/proc/tty/driver/$line" \
-			    | tail -n +2 | grep -oh "^\s*\S*[0-9]\+")
-		for active in $activetty; do
-			# If indexes do match then enable the serial console.
-			if [ $active -eq $runtime_tty ]
-			then
-				if [ -c /dev/$2 ]
-				then
-				    ${setsid:-} ${getty} -L $1 $2 $3
-				fi
-				break
-			fi
-		done
-	fi
-done
-
-# Restore $IFS.
-IFS=$DEFAULT_IFS