flash_fp_mcu: Clarify subshell func return behavior

Change functions whose return value we are interested in evaluating
to return (instead of exit).

Reserve exit syntax for explicit aborts from the script.

Fix get_platform_name error case.

BRANCH=none
BUG=none
TEST=scp util/flash_fp_mcu dut1:/usr/local/bin/flash_fp_mcu
     ssh dut1 flash_fp_mcu --hello
TEST=# Add "return 1" in the top of get_spiid function.
     scp util/flash_fp_mcu dut1:/usr/local/bin/flash_fp_mcu
     ssh dut1 flash_fp_mcu --hello
TEST=# Add "return 1" to the top of get_platform_name function.
     scp util/flash_fp_mcu dut1:/usr/local/bin/flash_fp_mcu
     ssh dut1 flash_fp_mcu --hello

Signed-off-by: Craig Hesling <hesling@chromium.org>
Change-Id: I3acc8ef3b345db4e77b2e151f90707336c2bcead
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2686925
Reviewed-by: Josie Nordrum <josienordrum@google.com>
Reviewed-by: Tom Hughes <tomhughes@chromium.org>

1 files changed, 11 insertions, 7 deletions

diff --git a/util/flash_fp_mcu b/util/flash_fp_mcu
index a6c489e72e..552606adef 100644
--- a/util/flash_fp_mcu
+++ b/util/flash_fp_mcu
@@ -54,17 +54,17 @@ get_spiid() {
   # TODO(b/179533783): Fix modalias on strongbad and remove this bypass.
   if [[ -n "${DEVICEID}" ]]; then
     echo "${DEVICEID}"
-    exit 0
+    return 0
   fi
 
   for dev in /sys/bus/spi/devices/*; do
     if [[ "$(cat "${dev}/modalias")" == "${CROS_EC_SPI_MODALIAS_STR}" ]]; then
       echo "$(basename "${dev}")"
-      exit 0
+      return 0
     fi
   done
 
-  exit 1
+  return 1
 }
 
 # Get the uartid for the fingerprint sensor based on the modalias
@@ -73,12 +73,12 @@ get_uartid() {
     if [ -f "${dev}/modalias" ]; then
       if [[ "$(cat "${dev}/modalias")" == "${CROS_EC_UART_MODALIAS_STR}" ]]; then
         echo "$(basename "${dev}")"
-        exit 0
+        return 0
       fi
     fi
   done
 
-  exit 1
+  return 1
 }
 
 # Usage: gpio <unexport|export|in|out|0|1|get> <signal> [signal...]
@@ -153,7 +153,7 @@ get_platform_name() {
   echo "Getting platform name from /etc/lsb-release." 1>&2
   platform_name="$(lsbval "CHROMEOS_RELEASE_BOARD")"
   if [[ -z "${platform_name}" ]]; then
-    exit 1
+    return 1
   fi
 
   echo "${platform_name}"
@@ -485,7 +485,11 @@ config_guybrush() {
 # function. Doing it in this manner allows us to reduce the number of
 # configurations that we have to maintain (and reduces the amount of testing
 # if we're only updating a specific config_<platform_name>).
-readonly PLATFORM_NAME="$(get_platform_name)"
+if ! PLATFORM_NAME="$(get_platform_name)"; then
+  echo "Failed to get platform name"
+  exit 1
+fi
+readonly PLATFORM_NAME
 
 echo "Using config for ${PLATFORM_NAME}"