functestlib: fix remoteproc firmware path lookup

Rework get_remoteproc_path_by_firmware() to iterate firmware files
directly and read them without using cat. This avoids the bogus idx
arithmetic that caused "operand expected" errors while still allowing
callers to derive the remoteproc index from the returned path.

Signed-off-by: Srikanth Muppandam <smuppand@qti.qualcomm.com>

Author: smuppand

Runner/utils/functestlib.sh

@@ -1900,15 +1900,35 @@ dt_has_remoteproc_fw() {
 }
 
 # Find the remoteproc path for a given firmware substring (e.g., "adsp", "cdsp", "gdsp").
+# Logic:
+#   - grep -n over /sys/class/remoteproc/remoteproc*/firmware (one line per remoteproc)
+#   - Take the first matching line number (1-based)
+#   - Subtract 1 → remoteproc index → /sys/class/remoteproc/remoteproc${idx}
 get_remoteproc_path_by_firmware() {
-    name="$1"
-    idx path
-    # List all remoteproc firmware nodes, match name, and return the remoteproc path
-    idx=$(cat /sys/class/remoteproc/remoteproc*/firmware 2>/dev/null | grep -n "$name" | cut -d: -f1 | head -n1)
-    [ -z "$idx" ] && return 1
-    idx=$((idx - 1))
-    path="/sys/class/remoteproc/remoteproc${idx}"
-    [ -d "$path" ] && echo "$path" && return 0
+    name=$1
+ 
+    [ -n "$name" ] || return 1
+    [ -d /sys/class/remoteproc ] || return 1
+ 
+    for fw in /sys/class/remoteproc/remoteproc*/firmware; do
+        # Skip if glob didn't match any file
+        [ -f "$fw" ] || continue
+ 
+        # Read first line from firmware file without using cat
+        if IFS= read -r fwname <"$fw"; then
+            case "$fwname" in
+                *"$name"*)
+                    # Map firmware file back to its remoteproc directory
+                    dir=${fw%/firmware}
+                    if [ -d "$dir" ]; then
+                        printf '%s\n' "$dir"
+                        return 0
+                    fi
+                    ;;
+            esac
+        fi
+    done
+ 
     return 1
 }