CODEWITHSUNDEEP
linuxlinux-kernellinux-device-driver
Neo
Neo

Reputation: 13891

Linux: Compiling a kernel device driver in standalone fashion

I'm compiling linux for an ARM board. I need to make some customized changes into an existing driver code present in the kernel repository and reload the driver.

I was expecting to find a ".ko" file in the driver directory after doing the make, but no such file exists. Apparently uImage/device tree image compilation doesn't work that way.

Do I need to write my own Makefile for standalone device driver compilation?

It may be a silly question, but sorry I'm pretty new to kernel/device drivers.

EDIT: I followed the process outlined here: http://odroid.com/dokuwiki/doku.php?id=en:c1_building_kernel After git checkout and installing the cross-compiler(arm-linux-gnueabihf-gcc 4.9.2), I issue the basic make comands

$ make odroidc_defconfig
$ make -j4
$ make -j4 modules
$ make uImage

All the steps are successful. The last few lines of log look like

KSYM    .tmp_kallsyms1.o
KSYM    .tmp_kallsyms2.o
LD      vmlinux
SORTEX  vmlinux
SYSMAP  System.map
OBJCOPY arch/arm/boot/ccImage
Kernel: arch/arm/boot/ccImage is ready
Image arch/arm/boot/ccImage.lzo is ready
UIMAGE  arch/arm/boot/uImage
Image Name:   Linux-3.10.72
Created:      Sat Mar 28 22:44:45 2015
Image Type:   ARM Linux Kernel Image (lzo compressed)
Data Size:    5459649 Bytes = 5331.69 kB = 5.21 MB
Load Address: 00208000
Entry Point:  00208000
Image arch/arm/boot/uImage is ready

EDIT 2: Path to the driver code https://github.com/hardkernel/linux/tree/odroidc-3.10.y/drivers/amlogic/efuse

Upvotes: 0

Views: 1982

Answers (2)

Vivek
Vivek

Reputation: 106

Not sure if you are still looking for the answers to this question.

But looking at the Kconfig file in your code, show that -

    config EFUSE 
        bool "EFUSE Driver"

And since all your driver files are compiled with this config, the above config description allows the CONFIG_EFUSE to be 'n' or 'y'. So you can only build static modules (build-in) with this.

All you need to do is change the above description to:

    config EFUSE 
        **tristate** "EFUSE Driver"

and also change the other configs in Kconfig to tristate. This will allow your driver to be compiled as module once you select the driver as 'M' in your kernel config. Then you should be able to see the ".ko" file corresponding to the driver.

Also do make sure to use EXPORT_SYMBOL(foo) when building the driver as module so that any dependencies are taken care of when loading module symbols.

Upvotes: 0

Chris Stratton
Chris Stratton

Reputation: 40357

Examining your Makefile

#                             
# Makefile for eFuse.         
#                             

obj-$(CONFIG_EFUSE) += efuse_bch_8.o efuse_version.o efuse_hw.o efuse.o

We learn that the code can be built as either a loadable module, or permanently linked into the kernel itself.

Examining odroidc_defconfig from branch odroidc-3.10.y-android mentioned in your instructions we find

#
# EFUSE Support
#
CONFIG_EFUSE=y

With the "y" indicating that the code is to be linked into the driver. Had it instead said "m" it would be built as a module.

It's possible you could change that in the kernel config, but it might also cause problems if there's nothing setup to load the module before it is needed.

Likely simply installing the newly built kernel with the code already linked inside (ie, forgetting about the module idea) will work.

Upvotes: 2

Related Questions