Getting a kernel module to load at start up

[asm2750]

I just finished building a petalinux 2014.2 test project and I was able to get a custom library and kernel module into the rootfs and on the image with no issues.

I am noticing however, that I still have to load the kernel module manually using insmod. Is there a a config setting I missed to have the OS load the module at start up, or do I have to write an init.d script to perform the action.

Thanks.

[balkris]

To have the PetaLinux build tools incorporate kernel modules, follow this general flow:

For PetaLinux 2013.10 and later:
 

Build-time Compiled Modules
 

1. Use the petalinux-create -t modules to create a module project.
   The new module will be located in ${PETALINUX}/components/modules/<MODULE>/.
2. Place the modules source code into ${PETALINUX_PROJECT}/components/modules/<MODULE>/
3. Modify the makefile located inside ${PETALINUX_PROJECT}/components/modules/<MODULE>/ as required.

Pre-built Kernel Modules
 

Ensure that the kernel module has been compiled for your PetaLinux target architecture (for example, MicroBlaze, ARM, etc.).
 

1. Use petalinux-create -t modules to create a module project.
   The new module will be located in ${PETALINUX_PROJECT}/components/modules/<MODULE>/.
2. Place the pre-built kernel modules into ${PETALINUX_PROJECT}/components/modules/<MODULE>/
3. Modify the makefile located in ${PETALINUX_PROJECT}/components/modules/<MODULE>/.
• Ensure that the all: and clean: sections of the makefile are empty.
• Update the install: section to copy the pre-built binaries into ${PETALINUX_PROJECT}/build/linux/rootfs/targetroot/.

An example of the modifications is as follows:

{{{
APP=myapp
all:

clean:

install: $(APP)
        $(TARGETINST) -d $(APP)-prebuilt /bin/$(APP) }}}

 
For PetaLinux 2013.04 and earlier:
 

Build-time Compiled Modules

1. Use the petalinux-new-module to create a module project.
   The new module will be located in ${PETALINUX}/software/user-modules/<MODULE>/.
2. Place the modules source code into ${PETALINUX}/software/user-modules/<MODULE>/
3. Modify the makefile located in ${PETALINUX}/software/user-apps/<APP>/ as needed.

Pre-built Kernel Modules

Ensure that the kernel modules have been compiled for your PetaLinux target architecture (e.g., MicroBlaze, ARM, etc.).

1. Use petalinux-new-module to create a module project.
   The new module will be located in ${PETALINUX}/software/user-modules/<MODULE>/.
2. Place the pre-built kernel modules into ${PETALINUX}/software/user-modules/<MODULE>/
3. Modify the makefile located inside ${PETALINUX}/software/user-apps/<APP>/.
• Ensure that the all:, install: and clean: sections of the makefile are empty.
• Update the romfs: section to copy the pre-built binaries into ${PETALINUX}/software/petalinux-dist/romfs/.

An example of the modifications is as follows:

{{{
APP=myapp
all:

clean:

romfs:
$(ROMFSINST) -d $(APP) /lib/modules/<KERNELRELEASE>/extra/
}}}

[vanmierlo]

Maybe I don't understand too well, but this answer tells how to add a kernel module to the rootfs, but not how to auto-load it at startup.

[asm2750 · Accepted solution]

Hi Vanmierlo,

I found the solution in this forum post:

https://forums.xilinx.com/t5/Embedded-Linux/petalinux-How-to-load-module-automatically-at-boot-time/m-p/636616/highlight/true#M13247

Adding the line to the install sectionof the makefile in the moduleproject will load the kernel module at boot:

$(TARGETINST) -d -a "module_name" /etc/modules