DTC tools, correct SYSCON LEDs

buildroot_config_fragment

@@ -39,3 +39,8 @@ BR2_PACKAGE_TRACE_CMD=y
 # GPIO: lsgpio, gpio-event-mon, gpio-hammer
 BR2_PACKAGE_LINUX_TOOLS=y
 BR2_PACKAGE_LINUX_TOOLS_GPIO=y
+
+# DTC
+BR2_PACKAGE_DTC=y
+BR2_PACKAGE_DTC_PROGRAMS=y
+BR2_PACKAGE_HOST_DTC=y

kernel_config_fragment

@@ -58,17 +58,11 @@ CONFIG_TRACER_SNAPSHOT=y
 # cat /sys/kernel/debug/kernel_page_tables
 CONFIG_X86_PTDUMP=y
 
-# LEDs.
+# LEDs. ARM only.
 #
-#     modprobe led-class
+#     cd /sys/class/leds/versatile:0
-#     modprobe leds-versatile
+#     cat max_brightness
-#     ls /sys/class/leds
+#     echo 255 >brightness
-#
-# TODO: the LEDs don't appear there. There are some entires under:
-#
-#     /sys/devices/platform/10000000.core-module/10000000.core-module:led@08.0/
-#
-# but they don't have brightness file.
 #
 # https://raspberrypi.stackexchange.com/questions/697/how-do-i-control-the-system-leds-using-my-software
 #
@@ -81,10 +75,24 @@ CONFIG_X86_PTDUMP=y
 #
 # - arch/arm/boot/dts/versatile-pb.dts
 # - drivers/leds/led-class.c
-# - drivers/leds/leds-versatile.c
+# - drivers/leds/leds-sysctl.c
 #
+# Try hacking QEMU's `hw/misc/arm_sysctl.c` with a printf:
+#
+#     static void arm_sysctl_write(void *opaque, hwaddr offset,
+#                                 uint64_t val, unsigned size)
+#     {
+#         arm_sysctl_state *s = (arm_sysctl_state *)opaque;
+#
+#         switch (offset) {
+#         case 0x08: /* LED */
+#             printf("LED val = %llx\n", (unsigned long long)val);
+#
+# to obeserve when the callback is made. But beware that one of the LEDs
+# has a heartbeat trigger by default (specified on dts), so it will produce a lot of output.
 CONFIG_LEDS_CLASS=y
 CONFIG_LEDS_CLASS_FLASH=y
+CONFIG_LEDS_SYSCON=y
 CONFIG_LEDS_TRIGGERS=y
 CONFIG_LEDS_TRIGGER_BACKLIGHT=y
 CONFIG_LEDS_TRIGGER_CPU=y
@@ -93,7 +101,6 @@ CONFIG_LEDS_TRIGGER_GPIO=y
 CONFIG_LEDS_TRIGGER_HEARTBEAT=y
 CONFIG_LEDS_TRIGGER_ONESHOT=y
 CONFIG_LEDS_TRIGGER_TIMER=y
-CONFIG_LEDS_VERSATILE=y
 CONFIG_NEW_LEDS=y
 
 # GPIO.

rootfs_overlay/gpio.sh

@@ -1,4 +1,5 @@
 #!/bin/sh
+# ARM only.
 # https://raspberrypi.stackexchange.com/questions/56373/is-it-possible-to-get-the-state-of-the-leds-and-gpios-in-a-qemu-emulation-like-t/69267#69267
 set -e
 cd /sys/class/gpio

run

@@ -41,8 +41,8 @@ env \
   O="$outdir" \
   BR2_JLEVEL="$(($(nproc) - 2))" \
   HOST_QEMU_OPTS="--enable-debug --enable-sdl --extra-cflags='-DDEBUG_PL061=1' --with-sdlabi=2.0" \
-  host-qemu-reconfigure \
   host-qemu-rebuild \
+  linux-rebuild \
   kernel_module-rebuild \
   all \
 ;