在我自己的meta层上将自己的设备驱动程序加载为Yocto中的内置功能

Question

I wrote my own USB driver for hardware and I want to add this driver as builtin. I have seen this post where they create a recipe to set as module and not builtin.

http://wiki.kaeilos.com/index.php/Howto_build_a_kernel_module_out_of_the_kernel_tree

Can you please guys help me in creating a recipe to set the module as builtin.

Thanks for your time.

Answer 1

You can't have external modules built into Linux Kernel. So you need to place your driver into drivers/usb/ (based on the hardware type it needs to be placed in drivers/usb/host/ if it is host controller driver or drivers/usb/dwc* or drivers/usb/gadget/udc if it is gadget driver) of your Linux Kernel tree.

Then you need to add according configuration in Kconfig and Makefile in drivers/usb . Finally you need to enable this as build in driver in defconfig/.config for building.

In short,

1. Place your driver in drivers/usb
2. Add Kconfig and Makefile . For example, CONFIG_USB_HW_HCD
3. Add to defconfig as CONFIG_USB_HW_HCD=y . In Yocto you can specify the defconfig file as file://defconfig in your SRC_URI .

EDIT: As you are using meta-intel directly, you can create patch and bbappend to it. To do it,

1. git clone "intel kernel repo"
2. Add driver as mentioned above. Copy to drivers/usb , add Kconfig, Makefile entry.
3. Add this driver to git repo using git add + git commit
4. Create patch using git format-patch
5. Create a .bbappend file and add this patch. You can place this .bbappend file in any of your custom layer or in meta-intel itself.
6. Add defconfig fragment also into the .bbappend file for your Linux Kernel.

This way you don't need to have separate repo of same Linux Kernel.

Answer 2

I hope your initial module will have module_init() and module_exit calls.

To make this usb module to be part of builtin kernel, very first thing is to modify you source code to remove module_init or module_exit calls add platform calls probe, init, etc./

Copy your source file to appropriate source directory like "driver/usb/*"

Add a entry in KCONFIG file with some description of that driver and also add rules for its dependencies

Add entry in Makefile for conditional compilation.

Configure your kernel using make menuconfig to enable your config tag and build your kernel