board/stm32mp157: remove hardcoded device tree names from post-image.sh

The post-image.sh script is used in several STM32MP157-based board
configs. It had hardcoded device tree file names for the supported
boards which were used for matching the expected TF-A binary name.
Replace this mechanism with a pair of grep and sed that build the TF-A
binary name from the device tree file name. For example, if
BR2_TARGET_ARM_TRUSTED_FIRMWARE_ADDITIONAL_VARIABLES contained
DTB_FILE_NAME=stm32mp157c-dk2.dtb, the appropriate TF-A file would be
named tf-a-stm32mp157c-dk2.stm32.

Since the Bash Here Strings are removed with this change, I took the
opportunity to remove the only other non-POSIX command, "local", and
then I was able to change the shebang to plain /bin/sh, with -eu for
simpler error handling.

Signed-off-by: Grzegorz Szymaszek <gszymaszek@short.pl>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

board/stmicroelectronics/common/stm32mp157/post-image.sh

@@ -1,4 +1,4 @@
-#!/usr/bin/env bash
+#!/bin/sh -eu
 
 #
 # atf_image extracts the ATF binary image from DTB_FILE_NAME that appears in
@@ -8,22 +8,18 @@
 #
 atf_image()
 {
-	local ATF_VARIABLES="$(sed -n 's/^BR2_TARGET_ARM_TRUSTED_FIRMWARE_ADDITIONAL_VARIABLES="\([\/a-zA-Z0-9_=. \-]*\)"$/\1/p' ${BR2_CONFIG})"
-
-	if grep -Eq "DTB_FILE_NAME=stm32mp157c-dk2.dtb" <<< ${ATF_VARIABLES}; then
-		echo "tf-a-stm32mp157c-dk2.stm32"
-	elif grep -Eq "DTB_FILE_NAME=stm32mp157a-dk1.dtb" <<< ${ATF_VARIABLES}; then
-                echo "tf-a-stm32mp157a-dk1.stm32"
-	elif grep -Eq "DTB_FILE_NAME=stm32mp157a-avenger96.dtb" <<< ${ATF_VARIABLES}; then
-                echo "tf-a-stm32mp157a-avenger96.stm32"
-	fi
+	ATF_VARIABLES="$(sed -n 's/^BR2_TARGET_ARM_TRUSTED_FIRMWARE_ADDITIONAL_VARIABLES="\([\/a-zA-Z0-9_=. \-]*\)"$/\1/p' ${BR2_CONFIG})"
+	# make sure DTB_FILE_NAME is set
+	printf '%s\n' "${ATF_VARIABLES}" | grep -Eq 'DTB_FILE_NAME=[0-9A-Za-z_\-]*'
+	# extract the value
+	DTB_FILE_NAME="$(printf '%s\n' "${ATF_VARIABLES}" | sed 's/.*DTB_FILE_NAME=\([a-zA-Z0-9_\-]*\)\.dtb.*/\1/')"
+	echo "tf-a-${DTB_FILE_NAME}.stm32"
 }
 
 main()
 {
-	local ATFBIN="$(atf_image)"
-	local GENIMAGE_CFG="$(mktemp --suffix genimage.cfg)"
-	local GENIMAGE_TMP="${BUILD_DIR}/genimage.tmp"
+	ATFBIN="$(atf_image)"
+	GENIMAGE_CFG="$(mktemp --suffix genimage.cfg)"
 
 	sed -e "s/%ATFBIN%/${ATFBIN}/" \
 		board/stmicroelectronics/common/stm32mp157/genimage.cfg.template > ${GENIMAGE_CFG}