How to make sure .ko are correct?

For Developers
#1

Hi,

I'm try to build kernel module on openwrt. So, I enable M on kernel part and enable * at openwrt.
When I try to insert module, show undefine symbol. So, I go back to kernel part, the ko include the symbol, but build_dir/stage_dir did not have the symbol.

$ grep -re cfg80211_connect_bss package/bbb/sdk/linux-4.9/net/wireless/cfg80211.ko build_dir/target-aarch64-linux-gnu_glibc/root-xxx/lib/modules/4.9.76-openwrt/cfg80211.ko staging_dir/target-aarch64-linux-gnu_glibc/root-xxx/lib/modules/4.9.76-openwrt/cfg80211.ko 
Binary file package/bbb/sdk/linux-4.9/net/wireless/cfg80211.ko matches

Looks like the cfg80211.ko are different, why? How do I fix/copy correct .ko to rootfs?
Please help. Thanks.

#2

Are you following the instructions from this page? Did you flash the device with the image you build or just try to copy over the corresponding .ko file?

#3

Hi darksky,

Yes, I followed the instructions of openwrt guide line.
Yes, I do flash the device with my build image, ko miss one symbol.
The symbol I can find it at linux/kernel folder, not at stage_dir/build_dir.
I do copy any ko from my changes. I just enable * at openwrt and M at kernel part.
Can you help me how to make sure ko is from kernel? Thanks.

#4

Double check the cfg80211.ko, looks like the ko come from backports-4.19.120-1.
So, it we want to porting new wifi driver, does it be need to adapt to backports-4.19.120-1?
Any document would be great to teach me how to porting new wifi driver. Thanks.

#5

Wireless drivers must be built against the corresponding backports (aka mac80211) package, which would be v5.7-rc3 based in master at the moment.

#6

So, Should I disable cfg80211 at kernel part, only enable cfg80211 at openwrt part? I think wifi driver will refer the backport, right? Thanks.

Now, I face the problem.

[  237.738204] cywdhd: Unknown symbol cfg80211_connect_bss (err 0)
[  237.745016] cywdhd: Unknown symbol __ieee80211_get_channel (err 0)

Double check the link, looks like kernel module still link the cfg80211 function from kernel.
How do I change the include/link path to compat-wireless? Thanks.

#7

Hi All,

I fix the issue of unknow symbol by

KBUILD_EXTRA_SYMBOLS:="${STAGING_DIR}/pkginfo/mac80211.symvers"
NOSTDINC_FLAGS:=\
       -I$(STAGING_DIR)/usr/include/mac80211 \
       -I$(STAGING_DIR)/usr/include/mac80211/uapi \
       -I$(STAGING_DIR)/usr/include/mac80211-backport \
       -include backport/backport.h

Thanks.