Fix MIPS BR2_PACKAGE_LINUX_TOOLS_GPIO build

Update mips for snapshot and initrd features.

Document MIPS limitations.

Improve description of test procedure

CONTRIBUTING.adoc

@@ -1,8 +1,25 @@
 = CONTRIBUTING
 
-Testing that should be done for every functional patch:
+== Testing
+
+Testing that should be done for every functional patch.
+
+=== Guest testing
+
+....
+./build
+./run -e '- lkmc_eval="/insrm.sh hello 5;wget -S google.com;poweroff;"' -n
+....
+
+Should:
+
+* boot
+* show `hello.ko` `init` and `exit` messages
+* make a network request
+* shutdown gracefully
+
+TODO automate all of this with a `/test-all.sh` script in guest which outputs to stdout `LKMC_TEST_PASS` or `LKMC_TEST_FAIL` and grep that from host.
+
+=== Host testing
 
-* `./build && ./run` boots
-* `/insrm.sh hello 5`. If a new module was added, use this for that module. Helps catch simple insert remove problems.
-* `wget -O- google.com` for Internet
 * `./run -d` and on another shell `./rungdb start_kernel` should break GDB at `start_kernel`

README.adoc

@@ -910,6 +910,16 @@ no module object found for ''
 ./build -a mips64
 ....
 
+Keep in mind that MIPS has the worst support our architectures due to the smaller community. Patches welcome as usual.
+
+TODOs:
+
+* networking is not working. See also:
+** https://stackoverflow.com/questions/21496449/networking-is-not-working-on-qemu-guest-malta-mips
+** https://unix.stackexchange.com/questions/208266/setting-up-qemu-and-mipsel-networking-trouble
+** https://unix.stackexchange.com/questions/354127/qemu-mips-and-debian
+* <<gdb>> does not work properly, does not find `start_kernel`
+
 === init
 
 When the Linux kernel finishes booting, it runs an executable as the first and only userland process.
@@ -1548,7 +1558,7 @@ Related: https://stackoverflow.com/questions/6405083/initrd-and-booting-the-linu
 
 ==== initramfs
 
-initramfs is just like initrd, but you also glue the image directly to the kernel image itself.
+initramfs is just like <<initrd>>, but you also glue the image directly to the kernel image itself.
 
 So the only argument that QEMU needs is the `-kernel`, no `-drive` not even `-initrd`! Pretty cool.
 
@@ -1710,7 +1720,7 @@ You can then restore CPU, memory and disk state back at any time.
 
 qcow2 filesystems must be used for that to work.
 
-To test it out, login into the VM, and run:
+To test it out, login into the VM with and run:
 
 ....
 /count.sh
@@ -1764,6 +1774,8 @@ cat f
 
 And the output is `0`.
 
+Our setup does not allow for snapshotting while using <<initrd>>.
+
 == Failed action
 
 === Record and replay

build

@@ -88,6 +88,11 @@ fi
 if $x11; then
   cat ../buildroot_config_fragment_x11 >> "${outdir}/.config"
 fi
+if [ "$arch" = 'mips64' ]; then
+  # Workaround for:
+  # http://lists.busybox.net/pipermail/buildroot/2017-August/201053.html
+  sed -Ei 's/^BR2_PACKAGE_LINUX_TOOLS_GPIO/BR2_PACKAGE_LINUX_TOOLS_GPIO=n/' "${outdir}/.config"
+fi
 make O="$outdir" olddefconfig
 # HOST_QEMU_OPTS is a hack that happens to work because the QEMU package luckly uses += at all times.
 # It shouldn't be necessary in the first place: https://bugs.busybox.net/show_bug.cgi?id=9936

run

@@ -116,12 +116,15 @@ $extra_flags \
 "
   ;;
   mips64)
+    if ! $initrd; then
+      root='root=/dev/hda'
+      extra_flags="$extra_flags -drive file='${images_dir}/rootfs.ext2.qcow2,format=qcow2'"
+    fi
     cmd="$qemu_common \
 -M malta \
 -append 'root=/dev/hda $extra_append' \
 -cpu I6400 \
 -device pcnet \
--drive file=${images_dir}/rootfs.ext2,format=raw \
 -kernel ${images_dir}/vmlinux \
 -nographic \
 $extra_flags \