[ImageBuilder][PATCH v3 3/3] uboot-script-gen: Enable not adding boot command to script

["Andrei Cherechesu (OSS)" <andrei.cherechesu@xxxxxxxxxxx>]

From: Andrei Cherechesu <andrei.cherechesu@xxxxxxx>

If the "BOOT_CMD" variable is set to "none" inside the config
file, the boot command (i.e. "booti") will not by added to the
generated script, to allow the user to customize the u-boot env
or the device-tree after executing the script commands and before
actually booting.

Added commands to store the addresses where the Xen image and
device-tree file are loaded, in 'host_kernel_addr' and 'host_fdt_addr'
variables, if BOOTCMD = "none".

The `booti` command can then be executed as part of the 'bootcmd' variable
in u-boot, which should contain:
        1. fetching the generated u-boot script
        2. executing the script
        3. running `booti ${host_kernel_addr} - ${host_fdt_addr}` command

Signed-off-by: Andrei Cherechesu <andrei.cherechesu@xxxxxxx>
---
 README.md                |  5 ++++-
 scripts/uboot-script-gen | 16 +++++++++++++---
 2 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/README.md b/README.md
index 3566a6d..07ad432 100644
--- a/README.md
+++ b/README.md
@@ -81,7 +81,10 @@ Where:
 
 - BOOT_CMD specifies the u-boot command used to boot the binaries.
   By default, it is 'booti'. The acceptable values are 'booti', 'bootm'
-  and 'bootefi'.
+  and 'bootefi' and 'none'. If the value is 'none', the BOOT_CMD is not
+  added to the boot script, and the addresses for the Xen binary and the
+  DTB are stored in 'host_kernel_addr' and 'host_fdt_addr' u-boot
+  env variables respectively, to be used manually when booting.
 
 - DEVICE_TREE specifies the DTB file to load.
 
diff --git a/scripts/uboot-script-gen b/scripts/uboot-script-gen
index f72551a..6a8a2b8 100755
--- a/scripts/uboot-script-gen
+++ b/scripts/uboot-script-gen
@@ -966,7 +966,7 @@ function check_depends()
 
 function check_boot_cmd()
 {
-    if ! [[ " bootm booti bootefi " =~ " ${BOOT_CMD}" ]]
+    if ! [[ " bootm booti bootefi none " =~ " ${BOOT_CMD}" ]]
     then
         echo "\"BOOT_CMD=$BOOT_CMD\" is not valid"
         exit 1
@@ -1251,9 +1251,19 @@ fi
 
 if test "$dynamic_loading_opt"
 then
-    echo "$BOOT_CMD \${host_kernel_addr} - \${host_fdt_addr}" >> $UBOOT_SOURCE
+    if [ "$BOOT_CMD" != "none" ]
+    then
+        echo "$BOOT_CMD \${host_kernel_addr} - \${host_fdt_addr}" >> 
$UBOOT_SOURCE
+    fi
 else
-    echo "$BOOT_CMD $kernel_addr - $device_tree_addr" >> $UBOOT_SOURCE
+    if [ "$BOOT_CMD" != "none" ]
+    then
+        echo "$BOOT_CMD $kernel_addr - $device_tree_addr" >> $UBOOT_SOURCE
+    else
+        # skip boot command but store load addresses to be used later
+        echo "setenv host_kernel_addr $kernel_addr" >> $UBOOT_SOURCE
+        echo "setenv host_fdt_addr $device_tree_addr" >> $UBOOT_SOURCE
+    fi
 fi
 
 if test "$FIT"
-- 
2.35.1