From a40f083a67098d4c19a1a46e4fd2a92b4752dd3b Mon Sep 17 00:00:00 2001
From: Namyoon Woo <namyoon@chromium.org>
Date: Wed, 15 May 2019 13:50:50 -0700
Subject: flash_ec: prevent null entry in dut-control recovery list

With some faulty platforms, dut-control might fail and
dut-control recovery list might have a null entry.
On flash_ec exit, the command run "dut-control ''" displays
a long error message, which confuses users.

This CL prevents that happening.

BUG=None
BRANCH=None
TEST=manually ran on hatch, scarlet and coral

Change-Id: I26b8c46b5ce6ff529cd368adeb6b24a01ed14566
Signed-off-by: Namyoon Woo <namyoon@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1614360
Reviewed-by: Matthew Blecker <matthewb@chromium.org>
---
 util/flash_ec | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/util/flash_ec b/util/flash_ec
index e55db51fd1..7bb5a463f4 100755
--- a/util/flash_ec
+++ b/util/flash_ec
@@ -622,8 +622,12 @@ declare -a save
 #   $2: (optional) Value to restore for the name at exit.
 #######################################
 function servo_save_add() {
+	local CTRL_RESULT=
 	case $# in
-		1) save+=( "$( "${DUT_CONTROL_CMD[@]}" "$@" )" )
+		1) CTRL_RESULT="$( "${DUT_CONTROL_CMD[@]}" "$@" )"
+		   if [[ -n "${CTRL_RESULT}" ]]; then
+			save+=( "${CTRL_RESULT}" )
+		   fi
 		   ;;
 		2) save+=( "$1:$2" )
 		   ;;
@@ -650,7 +654,9 @@ function servo_save() {
 function servo_restore() {
 	info "Restoring servo settings..."
 	for ctrl in "${save[@]}"; do
-		dut_control "$ctrl"
+		if [[ -n "${ctrl}" ]]; then
+			dut_control "${ctrl}"
+		fi
 	done
 }
 
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