LED failed attempt, GPIO working

README.md

@@ -47,10 +47,12 @@ If you are feeling fancy, you can also insert modules with:
 
     modprobe hello
 
-and if you are feeling raw, you can use:
+If you are feeling raw, you can use:
 
     /myinsmod.out /hello.ko
 
+Kernel modules built in-tree with `CONFIG_SOME_MOD=m`, are available via `modprobe`.
+
 We use `printk` a lot, and it shows on the QEMU terminal by default. If that annoys you (e.g. you want to see stdout separately), do:
 
     dmesg -n 1

kernel_config_fragment

@@ -57,3 +57,38 @@ CONFIG_TRACER_SNAPSHOT=y
 # https://stackoverflow.com/questions/20069620/print-kernels-page-table-entries
 # cat /sys/kernel/debug/kernel_page_tables
 CONFIG_X86_PTDUMP=y
+
+# LEDs.
+#
+#     modprobe led-class
+#     modprobe leds-versatile
+#     ls /sys/class/leds
+#
+# 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
+#
+# Relevant QEMU files:
+#
+# - hw/arm/versatilepb.c
+# - hw/misc/arm_sysctl.c
+#
+# Relevant kernel files:
+#
+# - arch/arm/boot/dts/versatile-pb.dts
+# - drivers/leds/led-class.c
+# - drivers/leds/leds-versatile.c
+#
+CONFIG_LEDS_CLASS=y
+CONFIG_LEDS_VERSATILE=y
+CONFIG_NEW_LEDS=y
+
+# GPIO.
+CONFIG_ARM_AMBA=y
+CONFIG_GPIOLIB=y
+CONFIG_GPIO_SYSFS=y
+CONFIG_GPIO_PL061=y

kernel_module/README.md

@@ -22,7 +22,9 @@
         1. [work_from_work](work_from_work.c)
     1.  [irq](irq.c)
     1.  Module dependencies
-        1. [dep.c](dep.c)
-        1. [dep2.c](dep2.c)
+        1. [dep](dep.c)
+        1. [dep2](dep2.c)
     1.  [character_device](character_device.c)
+    1.  Hardware device drivers
+        1. [pci](pci.c)
 1.  [user](user/)

rootfs_overlay/README.md

@@ -6,3 +6,7 @@ We use it to for things like:
 
 - customized configuration files
 - userland module test scripts
+
+Most tests correspond clearly to a given kernel module, but the following ones don't, e.g. they correspond to mainline tree features:
+
+- [gpio](gpio.sh)

rootfs_overlay/gpio.sh

@@ -0,0 +1,27 @@
+#!/bin/sh
+set -e
+cd /sys/class/gpio
+echo 480 > export
+echo 481 > export
+echo 482 > export
+echo 488 > export
+echo 496 > export
+echo out > gpio480/direction
+echo out > gpio481/direction
+echo out > gpio482/direction
+echo out > gpio488/direction
+echo out > gpio496/direction
+v=1
+while true; do
+  echo $v > gpio480/value
+  echo $v > gpio481/value
+  echo $v > gpio482/value
+  echo $v > gpio488/value
+  echo $v > gpio496/value
+  if [ $v -eq 1 ]; then
+    v=0
+  else
+    v=1
+  fi
+  sleep 1
+done

run

@@ -40,7 +40,8 @@ env \
   make \
   O="$outdir" \
   BR2_JLEVEL="$(($(nproc) - 2))" \
-  HOST_QEMU_OPTS="--enable-debug --enable-sdl --with-sdlabi=2.0" \
+  HOST_QEMU_OPTS="--enable-debug --enable-sdl --extra-cflags='-DDEBUG_PL061=1' --with-sdlabi=2.0" \
+  host-qemu-reconfigure \
   host-qemu-rebuild \
   kernel_module-rebuild \
   all \