Adding a kernel module for USB wifi adapter

A Former User

I was able to bypass this error by changing the offending line to vec = NULL;. There's a null check immediately after, so it shouldn't cause too much trouble (other than probably causing whatever logging this was supposed to do to stop working).

However, now it complains about there being no GCC 7. What? I compiled it just fine with 8.5.0 before...

I guess will try to compile 7.5.0 now.

A Former User

This issue disappears after make clean in the top directory. Looks like 7.5.0 isn't needed after all. Now I just need to fix cc1plus not being the right version.

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:

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