Linux: Modpost Does Not Build Anything

Linux: modpost does not build anything

The error mysteriously went away. If anyone has an idea what could cause this. I'd like to know in case there is a next time.

kernel driver external modules not building completely

I found the solution. I really misunderstood the error messages and how ".ko" modules interact with the kernel. An external module resolves externals (at least some) at compile/link time not at run time. This is why I get the 4 "ERRORS".

That said, my "GobiNet" is looking for external symbols not present in my Kernel set-up. A few quick greps allowed me to find it needed "drivers/net/usb/usbnet.c". This required CONFIG_USBNET = y to be set in the ".config" file (set through "make xconfig"). Hope it can help someone else.

EDIT: To answer the question about "a few quick greps". What I meant is I search all the source files containing the missing names. It will tell me what file defines that symbol. Then, I can find what variable should be set to "y" to include it in the compile. Here is an example:

grep -r --include="*.c" "usbnet_probe"

You execute that in the terminal from the folder you want to search from and down recursively (-r option). grep is extremely useful to find text in large amount of files. I often don't remember the specific but a quick Google search gives you how to perform some very tricky searches you never thought could be done so easily.

Problems building driver on Linux kernel 5.8.x

I am answering my own question in case it helps anyone else with this problem. Although it has never been an issue in the past, we've always had a warning that the corresponding .o.cmd file was not present for our .o_shipped files. This appears to be important in kernel 5.8 onwards and my fix was to add a touch command to the Kbuild file (i.e. "touch .driver.o.cmd"). This does not remove the warning but it allows the driver to build as normal.

Command 'make modules' doesn't build all modules

Ok, after several cups of coffee and lots of googling, I don't know how this all works yet, but looks like when I first upgraded the kernel, the .config was based on the running kernel's config and it includes all the needed modules, therefore it ran fine? Then somehow on the subsequent compilations almost all of the modules were not configured in the .config (except the 4 mentioned above). Long story short, I used the old .config and ran menuconfig to make additional changes, it seems to solve my problem. Thanks!

Kernel module not building .ko file

Ok, I have figured out the problem. I am having square bracket character "[" in the module source directory

LD [M]  /home/farshad/Work/CSP/boards/imx6q/ar6k3/ar6003_3.1_RC_Linux_release_[posted_2011_8_19_olca3.1RC_553/imx6build/host/os/linux/ar6000.o  

Removing this from the path worked well and I got my kernel module object files. I have renamed

ar6003_3.1_RC_Linux_release_[posted_2011_8_19_olca3.1RC_553 

to

ar6003, 

and also tested with

ar6003_3.1_RC_Linux_release_posted_2011_8_19_olca3.1RC_553

Both worked fine. I was building on Ubuntu 10.04. A colleague of mine has built from the same sources having "[" character in his path on Ubuntu 11.04 and kernel module object file was building nicely, this also suggest the changed behavior of grep / find / awk or such utility among their different versions, which kernel build system is using, resulting in this issue.

Regards,
Farrukh Arshad.

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