Adding a kernel module for USB wifi adapter

[Emphrath]

@zehkira Thank you so much for sharing your process here, despite the lack of help. I can't be of any help myself since I've never built a kernel in my life, but the process itself will be useful for a lot of people, so thanks ! Quick side note: if you plan to flash this on an actual device, bear in mind that most ubports devices are flashed aiming at a fixed partition size, dependant on the partition layout that the installer expects at first flash. There are ways to flash a bigger system image (which likely is what your hack will result in) but I don't think it's straightforward and you should research the forum before you attempt it. Good luck and keep us posted !

[A Former User]

I'm finally able to build without errors again. I didn't do anything with menuconfig this time though, just make clean && source build/envsetup.sh && mka. Again, it looks like the driver did not end up in the output:

root@ubports:~/ubp-5.1# cout
root@ubports:~/ubp-5.1/out/target/product/hammerhead# find . |grep mt7601u
root@ubports:~/ubp-5.1/out/target/product/hammerhead#

There is, however, obj/KERNEL_OBJ/include/config/wlan/vendor/mediatek.h. Which is empty.

Sidenote: I learned of the existence of ppa:ubuntu-toolchain-r/test, which I can use to install newer versions of GCC. No need to compile.

most ubports devices are flashed aiming at a fixed partition size, dependant on the partition layout that the installer expects at first flash.

Sounds like more pain.

[A Former User]

Running make ARCH=arm menuconfig and choosing to save on exit results in a .config file being created, which contains a setting to include the module I want. Will try to build with this file present now. So, immediately after the previous build I did this:

1. make clean in top directory to remove results of previous build.
2. make ARCH=arm menuconfig in kernel/lge/hammerhead.
3. mka in top directory to build again.

[A Former User]

It does not like that .config file being there.

 Using /root/ubp-5.1/kernel/lge/hammerhead as source for kernel
  /root/ubp-5.1/kernel/lge/hammerhead is not clean, please run 'make mrproper'
  in the '/root/ubp-5.1/kernel/lge/hammerhead' directory.
Copy: /root/ubp-5.1/out/target/product/hammerhead/system/etc/audio_policy.conf
Copy xml: /root/ubp-5.1/out/target/product/hammerhead/system/etc/mixer_paths.xml
/root/ubp-5.1/kernel/lge/hammerhead/Makefile:976: recipe for target 'prepare3' failed
make[2]: *** [prepare3] Error 1
Makefile:130: recipe for target 'sub-make' failed
make[1]: *** [sub-make] Error 2
make[1]: Leaving directory '/root/ubp-5.1/kernel/lge/hammerhead'
Copy xml: /root/ubp-5.1/out/target/product/hammerhead/system/etc/media_codecs_google_audio.xml
build/core/tasks/kernel.mk:277: recipe for target 'TARGET_KERNEL_BINARIES' failed

As further evidenced by what running the command it wants does:

root@ubports:~/ubp-5.1/kernel/lge/hammerhead# make mrproper
  CLEAN   scripts/basic
  CLEAN   scripts/kconfig
  CLEAN   include/config
  CLEAN   .config

But that file is supposed to be there, and I am doing this correctly, according to this article on kernel configuration.

[A Former User]

This time I used the make_defconfig.sh script in hammerhead/ instead of make ARCH=arm menuconfig. This script wants a config file from arch/arm/configs/ to edit. The problem is that there are 3 different configs for hammerhead:

• cyanogenmod_hammerhead_defconfig
• hammerhead_defconfig
• tct_hammer_defconfig (I guess this one says "hammer", not "hammerhead")

When I do uname -a on my Nexus, it says cyanogenmod in there, so I picked that one. Building now.

[A Former User]

Build was successful. Still no driver in the output though.

root@ubports:~/ubp-5.1/out/target/product/hammerhead# find . |grep -i mt76
root@ubports:~/ubp-5.1/out/target/product/hammerhead# find . |grep -i mediatek
./obj/KERNEL_OBJ/include/config/wlan/vendor/mediatek.h
root@ubports:~/ubp-5.1/out/target/product/hammerhead# cat ./obj/KERNEL_OBJ/include/config/wlan/vendor/mediatek.h
root@ubports:~/ubp-5.1/out/target/product/hammerhead# 

[A Former User]

This time I did ./make_defconfig.sh hammerhead_defconfig. Note how the changes made to the cyanogenmod file remain despite make clean and make mrproper:

	modified:   arch/arm/configs/cyanogenmod_hammerhead_defconfig
	modified:   arch/arm/configs/hammerhead_defconfig

Another potentially relevant thing I noticed: In the configuration menu provided by make_defconfig.sh, only a Mediatek group is shown. There is no entry for the mt7601u. This was not the case when I used make ARCH=arm menuconfig. Perhaps an indication of a configuration issue that is causing the driver to not be detected? But then why was it detected in the other case? Assuming this build fails to produce the desired result, I will investigate this next.

[A Former User]

I assumed correctly. Here is the section referencing Mediatek in the .config that make_defconfig.sh would generate:

CONFIG_WLAN_VENDOR_MEDIATEK=y

Compare the Broadcom (I think) drivers section:

CONFIG_BCMDHD=y
CONFIG_BCM4339=y
CONFIG_BCMDHD_FW_PATH="/vendor/firmware/fw_bcmdhd.bin"
CONFIG_BCMDHD_NVRAM_PATH="/etc/wifi/bcmdhd.cal"

And the Mediatek section in a .config I generated with make ARCH=arm menuconfig:

CONFIG_WLAN_VENDOR_MEDIATEK=y
CONFIG_MT7601U=m

I'll try to simply manually add these two lines to hammerhead_defconfig and cyanogenmod_hammerhead_defconfig for the next build.

[A Former User]

Found this in the mt7601u's Kconfig:

	depends on MAC80211
	depends on USB

mac80211 is something that can be selected in the config menu in Networking support → Wireless. It is not selected by default. When you select it, the mt7601u driver appears in the Mediatek wireless driver section of the menu as it should.

I edited both hammerhead_defconfig and cyanogenmod_hammerhead_defconfig like this (using make_defconfig.sh of course). Building again.

[A Former User]

Build finished. Seemingly no change. Maybe out/ is supposed to be like this. Will flash tomorrow and check.

[A Former User]

Flashed and checked with lsmod, modinfo and find. It looks like, despite everything, the module was still not installed.

[A Former User]

device/lge/hammerhead/BoardConfig.mk confirms that the configuration file I've been working with is the right one:

# Define kernel config for inline building
TARGET_KERNEL_CONFIG := cyanogenmod_hammerhead_defconfig
TARGET_KERNEL_SOURCE := kernel/lge/hammerhead

device/lge/hammerhead/init.hammerhead.rc has something that could be relevant:

  # wifi
    chown wifi system /persist/wifi
    insmod /system/lib/modules/bcmdhd.ko

I'll add another insmod line for mt7601u and see what happens. My guess is it will either break something or do nothing.

[A Former User]

I tried mkap, which failed to push anything to the device, but it did create ./out/target/product/hammerhead/obj/KERNEL_OBJ/include/config/mt7601u.h. I also noticed that all the .h files in obj/KERNEL_OBJ/include/config/ are empty.

Flashed, replaced system image, no change.

[A Former User]

I am literally unable to tell you what happened next, because all my posts are being flagged as spam.

[Emphrath]

@zehkira maybe because of external links. Happens sometimes.

[A Former User]

I'm out of ideas.

[cliffcoggin]

@zehkira I congratulate you on your remarkable persistence, even though I have little understanding of what you have been doing.