Adding a kernel module for USB wifi adapter

A Former User

I am currently unable to build the kernel due to errors. This is my process after initializing and syncing ubp-5.1-allthefixings. As mentioned before, I'm following this official guide.

Go to kernel/lge/hammerhead/
Add driver files from torvalds/linux and add entries for them in Kconfig and Makefile files in drivers/net/wireless/

	new file:   mediatek/Kconfig
	new file:   mediatek/Makefile
	new file:   mediatek/mt7601u/Kconfig
	new file:   mediatek/mt7601u/Makefile
	new file:   mediatek/mt7601u/core.c
	new file:   mediatek/mt7601u/debugfs.c
	new file:   mediatek/mt7601u/dma.c
	new file:   mediatek/mt7601u/dma.h
	new file:   mediatek/mt7601u/eeprom.c
	new file:   mediatek/mt7601u/eeprom.h
	new file:   mediatek/mt7601u/init.c
	new file:   mediatek/mt7601u/initvals.h
	new file:   mediatek/mt7601u/initvals_phy.h
	new file:   mediatek/mt7601u/mac.c
	new file:   mediatek/mt7601u/mac.h
	new file:   mediatek/mt7601u/main.c
	new file:   mediatek/mt7601u/mcu.c
	new file:   mediatek/mt7601u/mcu.h
	new file:   mediatek/mt7601u/mt7601u.h
	new file:   mediatek/mt7601u/phy.c
	new file:   mediatek/mt7601u/regs.h
	new file:   mediatek/mt7601u/trace.c
	new file:   mediatek/mt7601u/trace.h
	new file:   mediatek/mt7601u/tx.c
	new file:   mediatek/mt7601u/usb.c
	new file:   mediatek/mt7601u/usb.h
	new file:   mediatek/mt7601u/util.c

diff --git a/drivers/net/wireless/Kconfig b/drivers/net/wireless/Kconfig
index 5ccdd2a..2c6f2ab 100644
--- a/drivers/net/wireless/Kconfig
+++ b/drivers/net/wireless/Kconfig
@@ -333,5 +333,6 @@ source "drivers/net/wireless/wl1251/Kconfig"
 source "drivers/net/wireless/wl12xx/Kconfig"
 source "drivers/net/wireless/zd1211rw/Kconfig"
 source "drivers/net/wireless/mwifiex/Kconfig"
+source "drivers/net/wireless/mediatek/Kconfig"
 
 endif # WLAN
diff --git a/drivers/net/wireless/Makefile b/drivers/net/wireless/Makefile
index 9392311..437e6b3 100644
--- a/drivers/net/wireless/Makefile
+++ b/drivers/net/wireless/Makefile
@@ -66,3 +66,5 @@ obj-$(CONFIG_BRCMSMAC)        += brcm80211/
 
 obj-$(CONFIG_LIBRA_SDIOIF)     += libra/
 obj-$(CONFIG_WCNSS_CORE)       += wcnss/
+
+obj-$(CONFIG_MEDIATEK) += mediatek/

make ARCH=arm menuconfig. Confirm the driver appears. Note that it is selected by default. Exit picking "yes" when asked to save configuration.

[*]   MediaTek devices (NEW)
<M>     MediaTek MT7601U (USB) support

Return to the top directory as required by the guide.
source build/envsetup.sh. No errors.

including device/oneplus/bacon/vendorsetup.sh
including device/lge/hammerhead/vendorsetup.sh
including device/lge/mako/vendorsetup.sh
including device/fairphone/FP2/vendorsetup.sh
including vendor/cm/vendorsetup.sh
including sdk/bash_completion/adb.bash
including vendor/cm/bash_completion/git.bash
including vendor/cm/bash_completion/repo.bash

lunch. The guide says to pick cm_...-userdebug. However, there is no such option for hammerhead, so I pick aosp_hammerhead-userdebug (number 5) instead.

Which would you like? [aosp_arm-eng] 5
Trying dependencies-only mode on a non-existing device tree?

============================================
PLATFORM_VERSION_CODENAME=REL
PLATFORM_VERSION=5.1.1
CM_VERSION=
TARGET_PRODUCT=aosp_hammerhead
TARGET_BUILD_VARIANT=userdebug
TARGET_BUILD_TYPE=release
TARGET_BUILD_APPS=
TARGET_ARCH=arm
TARGET_ARCH_VARIANT=armv7-a-neon
TARGET_CPU_VARIANT=krait
TARGET_2ND_ARCH=
TARGET_2ND_ARCH_VARIANT=
TARGET_2ND_CPU_VARIANT=
HOST_ARCH=x86_64
HOST_OS=linux
HOST_OS_EXTRA=Linux-4.4.0-210-generic-x86_64-with-glibc2.23
HOST_BUILD_TYPE=release
BUILD_ID=LMY48W
OUT_DIR=/root/ubp-5.1/out
============================================

Finally, mka. Previously (before I broke my old VM) I was able to build just fine, except the driver would not be included in the output for some reason. Now (on a fresh VM) I'm getting the following error:

system/core/liblog/fake_log_device.c: In function ‘showLog.isra.0’:
system/core/liblog/fake_log_device.c:463:30: error: argument 1 value ‘4294967288’ exceeds maximum object size 2147483647 [-Werror=alloc-size-larger-than=]
         vec = (struct iovec*)malloc(sizeof(struct iovec)*numVecs);
                              ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from system/core/liblog/fake_log_device.c:27:
/usr/include/stdlib.h:466:14: note: in a call to allocation function ‘malloc’ declared here
 extern void *malloc (size_t __size) __THROW __attribute_malloc__ __wur;
              ^~~~~~
cc1: all warnings being treated as errors
build/core/binary.mk:699: recipe for target '/root/ubp-5.1/out/host/linux-x86/obj32/STATIC_LIBRARIES/liblog_intermediates/fake_log_device.o' failed

...

#### make failed to build some targets (53 seconds) ####

Additional information:

root@ubports:~/ubp-5.1# cc --version
cc (GCC) 8.5.0
Copyright (C) 2018 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

root@ubports:~/ubp-5.1# python --version
Python 2.7.12

root@ubports:~/ubp-5.1# uname -a
Linux ubports 4.4.0-210-generic #242-Ubuntu SMP Fri Apr 16 09:57:56 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux

root@ubports:~/ubp-5.1/kernel/lge/hammerhead# update-alternatives --list cc
/usr/local/bin/x86_64-pc-linux-gnu-gcc-8.5.0

root@ubports:~/ubp-5.1/kernel/lge/hammerhead# update-alternatives --list cc1
/usr/local/libexec/gcc/x86_64-pc-linux-gnu/8.5.0/cc1

Any help would be appreciated.

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.