default-distrovars: Have KERNEL_CONSOLE reference SERIAL_CONSOLES

Currently, KERNEL_CONSOLE has a default value of "ttyS0".  However, Arm
machines and those using virtio serial prefer to use "ttyAMA0" or "hvc0"
(or something else).  These are usually defined by the machine config
file as SERIAL_CONSOLES, which has one or more entries.  Take the first
one of those instead of ttyS0, but default back to ttyS0 if nothing is
set.

Also, use this variable in the efi wic file instead of "ttyS0".
Of note, this changes the default speed of the default kernel console
from undefined (9600) to 115200.  This allows for users of the
mkefidisk.wks to work as before but any users of this variable could see
changed behavior and would now need to define this as:
KERNEL_CONSOLE ?= "ttyS0,9600"

This includes revisions suggested by Quentin Schulz and Ross Burton.

(From OE-Core rev: da42fc9ad55d1d60a04e38ff94c965f711f60cd6)

Signed-off-by: Jon Mason <jdmason@kudzu.us>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/classes-recipe/image_types_wic.bbclass

@@ -26,6 +26,7 @@ WICVARS ?= "\
 	INITRD \
 	INITRD_LIVE \
 	ISODIR \
+	KERNEL_CONSOLE \
 	KERNEL_IMAGETYPE \
 	MACHINE \
 	PSEUDO_IGNORE_PATHS \

meta/conf/distro/include/default-distrovars.inc

@@ -1,7 +1,8 @@
 QA_LOGFILE = "${TMPDIR}/qa.log"
 
 OEINCLUDELOGS ?= "yes"
-KERNEL_CONSOLE ?= "ttyS0"
+# if SERIAL_CONSOLES is set, take the first device entry.  Otherwise use ttyS0 as the default
+KERNEL_CONSOLE ?= "${@','.join(d.getVar('SERIAL_CONSOLES').split(' ')[0].split(';')[::-1]) or 'ttyS0,115200'}"
 KEEPUIMAGE ??= "yes"
 
 DEFAULT_IMAGE_LINGUAS = "en-us en-gb"

scripts/lib/wic/canned-wks/mkefidisk.wks

@@ -8,4 +8,4 @@ part / --source rootfs --ondisk sda --fstype=ext4 --label platform --align 1024
 
 part swap --ondisk sda --size 44 --label swap1 --fstype=swap
 
-bootloader --ptable gpt --timeout=5 --append="rootfstype=ext4 console=ttyS0,115200 console=tty0"
+bootloader --ptable gpt --timeout=5 --append="rootfstype=ext4 console=${KERNEL_CONSOLE} console=tty0"