target: Speed-up read_tree_values()

Since target.read_tree_values() has been modified to use tar as a way to
fetch the content of files from the target, it is more robust, but also
much slower. Since that level of robustness is in practice required only
for very specific use-cased, re-introduce the old way of doing read_tree
using find and grep.

read_tree_values() gains a new parameter to specify how files should be
read from the target, with or without tar. It defaults to the old way
of doing things.

Signed-off-by: Quentin Perret <quentin.perret@arm.com>

devlib/bin/scripts/shutils.in

@@ -255,6 +255,28 @@ sched_get_kernel_attributes() {
 # Misc
 ################################################################################
 
+read_tree_values() {
+    BASEPATH=$1
+    MAXDEPTH=$2
+
+    if [ ! -e $BASEPATH ]; then
+        echo "ERROR: $BASEPATH does not exist"
+        exit 1
+    fi
+
+    PATHS=$($BUSYBOX find $BASEPATH -follow -maxdepth $MAXDEPTH)
+    i=0
+    for path in $PATHS; do
+        i=$(expr $i + 1)
+        if [ $i -gt 1 ]; then
+            break;
+        fi
+    done
+    if [ $i -gt 1 ]; then
+        $BUSYBOX grep -s '' $PATHS
+    fi
+}
+
 read_tree_tgz_b64() {
     BASEPATH=$1
     MAXDEPTH=$2
@@ -353,6 +375,9 @@ ftrace_get_function_stats)
 hotplug_online_all)
 	hotplug_online_all
     ;;
+read_tree_values)
+	read_tree_values $*
+    ;;
 read_tree_tgz_b64)
 	read_tree_tgz_b64 $*
     ;;