Add LED indication for button handling in Yellow's U-Boot (#3536)

With #3523 as inspiration, it might be useful to wait for buttons to be
released, e.g. in case when they become stuck. Also indicate the button
operation (wipe, boot files removal, UMS) has been handled by turning on the
yellow LED.

buildroot-external/board/raspberrypi/yellow/uboot-boot64.ush

@@ -23,21 +23,29 @@ test -n "${MACHINE_ID}" || setenv BOOT_CONDITION "systemd.condition-first-boot=t
 # HassOS bootargs
 setenv bootargs_hassos "zram.enabled=1 zram.num_devices=3 rootwait systemd.machine_id=${MACHINE_ID} cgroup_enable=memory fsck.repair=yes ${BOOT_CONDITION}"
 
+setenv confirm_reset_handled ' \
+    led usr on; \
+    echo "Waiting for red button to be released";
+    while gpio input GPIO27; do sleep 0.5; done;'
+
 # Red Button pressed?
 if gpio input GPIO27; then
   sleep 1
   # ... and Blue Button Pressed?
   if gpio input GPIO26; then
     echo "Boot wipe has been pressed, deleting boot files to trigger USB boot..."
+    run confirm_reset_handled
     fatrm ${devtype} ${devnum}:1 /start4.elf
     reset
   fi
   # Red still pressed?
   if gpio input GPIO27; then
     echo "Device wipe button has been pressed, setting wipe flag..."
+    run confirm_reset_handled
     setenv bootargs_hassos "${bootargs_hassos} haos.wipe=1"
   fi
 elif gpio input GPIO26; then
+  led usr on
   ums 0 ${devtype} ${devnum}
 fi
 

buildroot-external/board/raspberrypi/yellow/uboot.config

@@ -1 +1,5 @@
 CONFIG_CMD_USB_MASS_STORAGE=y
+
+CONFIG_LED=y
+CONFIG_LED_GPIO=y
+CONFIG_CMD_LED=y