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✏️ Editing: framebuffer

#!/bin/sh

# shellcheck disable=SC2034
OPTION=FRAMEBUFFER
PREREQ="udev"
prereqs()
{
	echo "$PREREQ"
}
case $1 in
# get pre-requisites
prereqs)
	prereqs
	exit 0
	;;
esac

# The options part of the kernel "video=" argument (i.e. everyting
# after "video=<fbdriver>:") has very inconsistent rules.
#
# Generally the following applies:
# 1) options are comma-separated
# 2) options can be in either of these three forms:
#    <arg>=<value>, <arg>:<value>, <boolean-arg>.
# 3) the "mode" option has the form <xres>x<yres>[M][R][-<bpp>][@<refresh>][i][m]
#    and may or may not start with "mode="
#
# When the options are used with modules, they need to be space-separated
# and the following conversions are needed:
#	<arg>:<value> -> <arg>=<value>
#	<boolean-arg> -> <boolean-arg>=1
#	<modevalue>   -> mode=<modevalue>
parse_video_opts()
{
	local OPTS="$1"
	local IFS=","

# Must be a line like video=<fbdriver>:<opt1>,[opt2]...
	if [ "${OPTS}" = "${OPTS%%:*}" ]; then
		return
	fi
	OPTS="${OPTS#*:}"
	for opt in ${OPTS}; do
		# Already in the "<arg>=<value>" form
		if [ "${opt}" != "${opt#*=}" ]; then
			echo -n "$opt "
		# In the "<arg>:<value>" form
		elif [ "${opt}" != "${opt#*:}" ]; then
			echo -n "${opt%:*}=${opt#*:} "
		# Presumably a modevalue without the "mode=" prefix
		elif [ "${opt}" != "${opt#[0-9]*x[0-9]}" ]; then
			echo -n "mode=$opt "
		# Presumably a boolean
		else
			echo -n "${opt}=1 "
		fi
	done
}

FB=""
OPTS=""

# shellcheck disable=SC2013
for x in $(cat /proc/cmdline); do
	case ${x} in
	vga=*)
		FB="vesafb";
		OPTS="";
		;;
	video=*)
		FB=${x#*=}
		FB="${FB%%:*}"
		OPTS="$(parse_video_opts "${x}")"
	esac
done

# Map command line name to module name
case ${FB} in
matroxfb)
	FB=matroxfb_base
	;;
esac

if [ -n "${FB}" ]; then
	# Some framebuffer devices need character devices :-/
	udevadm settle
	# shellcheck disable=SC2086
	MODPROBE_OPTIONS=-q modprobe ${FB} ${OPTS}
	# Wait for the framebuffer devices to be ready
	udevadm settle
else
	# If we have no graphics devices yet, wait for udev to settle
	[ -d /sys/class/graphics/fbcon ] && \
	[ -d /sys/class/graphics/fb0   ] && \
	[ -d /sys/class/drm/card0      ] || udevadm settle

# If we still have no graphics device, fall back to vesafb like
	# we do in the post-initramfs case in
	# /etc/init/udev-fallback-graphics.conf.
	# There is a higher risk of racing the regular video driver init
	# than there is in the post-initramfs case, because this is earlier
	# in boot and the kernel has had less time to finish probing the
	# video drivers; and if we probe vesafb when we aren't meant to it
	# will cause problems later.  So just to be sure, add a sleep(1)
	# which seems to be enough time to let the drm interface get loaded.
	[ -d /sys/class/graphics/fbcon ] && \
	[ -d /sys/class/graphics/fb0   ] && \
	[ -d /sys/class/drm/card0      ] || sleep 1

if    ! [ -d /sys/class/graphics/fbcon ] \
	   || ! [ -d /sys/class/graphics/fb0   ] \
	   || ! [ -d /sys/class/drm/card0      ]
	then
		modprobe -q vesafb 2>/dev/null
		udevadm settle
	fi
fi

# Force fb mode via /sys interface
# shellcheck disable=SC2013
for x in $(cat /proc/cmdline); do
	case ${x} in
	fbmode=*)
		MODE=${x#*=}
		echo "$MODE" > /sys/class/graphics/fb0/mode
		;;
	esac
done

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