I was experimenting with building the Linux kernel (3.18) for the Debian (Jessie) 15.06 release. I referred to the instructions in section 7 of the Getting Started guide, and thought it might be helpful to add some clarification to a few of the steps, since a few things were unclear the first time around.
First of all, here's the cross-compile build environment I used:
Linux acencini-GA-970A-D3 3.16.0-43-generic #58~14.04.1-Ubuntu SMP Mon Jun 22 10:21:20 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux
The toolchain I used was the x86_64 version:
As opposed to using the i386/multiarch version. Setup was similar to the instructions on the page - added toolchain to PATH, and noted for future use elsewhere (see below).
After installing the toolchain:
git clone https://github.com/96boards/linux.git linux.git
git checkout 96boards-hikey-15.06
git clone https://github.com/96boards/wilink8-wlan_build-utilites.git build_utilities.git
git clone -b hikey https://github.com/96boards/wilink8-wlan_wl18xx.git build_utilities.git/src/driver
git clone -b R8.5 https://github.com/96boards/wilink8-wlan_wl18xx_fw.git build_utilities.git/src/fw_download
git clone -b hikey https://github.com/96boards/wilink8-wlan_backports.git build_utilities.git/src/backports
patch -p1 < build_utilities.git/patches/hikey_patches/0001-defconfig-hikey-discard-CFG80211-and-MAC80211.patch
This was largely similar to the instructions, but is keyed to a newer build.
Perhaps the most unclear thing in the documentation was how to set up build_utilities.git/setup-env, specifically, which environment variables to set, and what to set them to. For this, I did the following:
cp build_utilities.git/setup-env.sample build_utilities.git/setup-env
Then, I set the following things within setup-env:
left KERNEL_VARIANT alone. Finally:
Then I went through the build process as follows:
make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- defconfig
Note: I modified defconfig to meet the needs of my custom kernel prior to the make above.
make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- -j8 Image modules hi6220-hikey.dtb
At this point, things compile happily.
Next, making the modules worked smoothly using the following steps (from linux.git):
make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- -j8 modules INSTALL_MOD_PATH=./build_utilities.git/fs modules_install
In the documentation, it says to ignore warnings/errors that may occur. This was a little vague. Specifically, the warnings/errors I encountered on this build were related to a few patch failures, specifically:
acencini@acencini-GA-970A-D3:~/hikey/linux.git/build_utilities.git$ ./build_wl18xx.sh modules
Changing ROOTFS path to /home/acencini/hikey/linux.git/build_utilities.git/fs
Using user defined kernel
Makefile was found. Kernel version was set to 3.18.0.
***** building only Driver modules *****
Copy original source files ...
Apply patches ...
Failed to apply changes from backport-adjustments/flow_dissector.patch
> patching file compat/net-core-flow_dissector.c
> Hunk #1 FAILED at 177.
> 1 out of 1 hunk FAILED -- saving rejects to file compat/net-core-flow_dissector.c.rej
Failed to apply changes from collateral-evolutions/network/85-hid_ll_driver/net_bluetooth_hidp_core.patch
> patching file net/bluetooth/hidp/core.c
> Hunk #1 succeeded at 268 with fuzz 1 (offset 45 lines).
> Hunk #2 succeeded at 353 with fuzz 2 (offset 45 lines).
> Hunk #3 FAILED at 396.
> Hunk #4 succeeded at 474 with fuzz 2 (offset 65 lines).
> Hunk #5 FAILED at 739.
> 2 out of 5 hunks FAILED -- saving rejects to file net/bluetooth/hidp/core.c.rej
Failed to apply changes from collateral-evolutions/network/86-qdisc_tx_busylock/ieee802154.patch
> patching file net/ieee802154/6lowpan.c
> Hunk #1 FAILED at 530.
> Hunk #2 FAILED at 545.
> 2 out of 2 hunks FAILED -- saving rejects to file net/ieee802154/6lowpan.c.rej
As well as a couple warnings in the compilation process later. An incorrectly configured setup_env results in other warnings/errors, so it might help to be specific about what are "ok" warnings/errors vs bad ones.
Building the firmware was smooth and successful as well.
Finally, these steps work fine:
sudo chown -R root:root *
sudo tar jcvf fw-modules.tar.bz2 *
However, at this point, I deviated from the process to what (for me) was an easier method for propping the files into the HiKey build image:
From some staging location (e.g. home directory), I download and dd the existing 15.06 image to an SD card - this requires an SD card reader on the build box.
gzip -d -c hikey-jessie_developer_20150701-323.img.gz > /tmp/jessie.img
sudo dd bs=4M if=/tmp/jessie.img of=/dev/sdb
(Note that all partitions on the SD card should be unmounted, and the device to write to may vary from system to system).
When complete, I mounted the /boot and /rootfs partitions, and did the following:
sudo tar xvf /path/to/build_utils/fs/lib/fw-modules.tar.bz2
This drops the modules and firmware into the appropriate place on the rootfs /lib.
It should also be noted that there are two stale links that could be cleaned up (/lib/modules/3.18.0-linaro-hikey/build and /lib/modules/3.18.0-linaro-hikey/source both point to locations on the build machine - these could be removed)
While in there, I also update /etc/network/interfaces.d/wlan0 to my wifi config...
Finally, I copy over the kernel
sudo cp /path/to/linux.git/arch/arm64/boot/Image .
And unmount the SD card partitions, and off we go.
TLDR: The setup_env instructions and module build details are vague, it might be easier to use x86_64 toolchain on cross-compile system, and using a mounted clean-image SD card via SD card reader may help improve the documentation on kernel building.
Anyway, that's my $0.02. Hopefully this helps - feedback welcome, and apologies in advance for any mistakes. Thought I'd share this.