#!/bin/bash

# set -x

if [[ "$(uname -m)" == arm* || "$(uname -m)" == aarch64 ]]

then

COMMAND="$1"

KERNEL_VERSION="$2"

#BOOT_DIR_ABS="$3"

#KERNEL_IMAGE="$4"

[ -f /etc/u-boot.conf ] && source /etc/u-boot.conf || true

[ -z "$FIRMWAREDT" ] || FirmwareDT=$FIRMWAREDT

if [[ $FirmwareDT == "True" ]]

then

	# if we want to use firmware DT we remove symlink to current kernel DT

        if [ -h /boot/dtb ]; then

            rm -f /boot/dtb

        fi

	exit 0

fi

# Setup a /boot/dtb -> /boot/dtb-$newest_kernel_version symlink so that

# u-boot can find the correct dtb to load.

#

# If invoked to 'add' a new kernel, find the newest based on `sort`ing

# the kernel versions dtb.  If 'remove', then follow basically the same

# procedure but exclude the version currently being removed.

#

# The theory of operation here is that, while newer kernels may add new

# dtb nodes and fields, as upstreaming hw support for some particular

# device progresses, it should never make backward incompatible changes.

# So it should always be safe to use a newer dtb with an older kernel.

    list_dtb_versions() {

        excluded_version="$1"

        for dtbdir in /boot/dtb-*; do

            dtbver=${dtbdir#*-}

            if [ "$dtbver" != "$excluded_version" ]; then

                echo $dtbver

            fi

        done

    }

    setup_dtb_link() {

        ver=`list_dtb_versions $1 | sort -r --sort=version | head -1`

        if [ -h /boot/dtb ]; then

            rm -f /boot/dtb

        fi

        ln -s dtb-$ver /boot/dtb

    }

    ret=0

    case "$COMMAND" in

        add)

            # If we're adding a kernel we want that version

            if [ -h /boot/dtb ]; then

                rm -f /boot/dtb

            fi

            ln -s dtb-$KERNEL_VERSION /boot/dtb

            ret=$?

            ;;

        remove)

            setup_dtb_link $KERNEL_VERSION

            ret=$?

            ;;

    esac

    exit $ret

else

    # Just exit on non ARM

    exit 0

fi