Yocto Recipe for automatically loading Out of Tree Linux Device Drivers on Start

-
We can instruct Yocto to automatically start our own Linux Kernel Module on Start.

Steps:

 1. Create a folder 'recipes-kernel' in your own custom meta layer if it doesn't exist
$ mkdir recipes-kernel
2. Inside 'recipes-kernel', create a folder 'my-module' for storing recipe and device driver files
$ cd recipes-kernel; mkdir my-module
3. Inside 'my-module', create 'files' folder and copy your device driver files
$ cd my-module; mkdir files
4. Copy this Makefile in the 'files' directory

5. Come back to the parent folder (i.e., my-module) and create a recipe for building the module
$ cd .. ; touch my-module_0.1.bb

You should have the following tree after this step.

6. Add this module into your configuration file (local.conf file or machine.conf)
MACHINE_ESSENTIAL_EXTRA_RDEPENDS += "kernel-module-mymod"
KERNEL_MODULE_AUTOLOAD += "mymod"

MACHINE_ESSENTIAL_EXTRA_RDEPENDS tells yocto to build this module and include it in the build image 
KERNEL_MODULE_AUTOLOAD is to load the module automatically on start

Comments

Post a Comment

Popular posts from this blog

bb.utils.contains yocto

-
Image
bb.utils.contains  is most commonly used function in Yocto. grep in poky directory returned with 696 count. $ grep -nr 'bb.utils.contains' poky/ | wc -l 696 It's definition is present in 'poky/bitbake/lib/bb/utils.py' file This function returns third argument if the second argument is subset of the first argument else returns fourth argument Let's take an example to understand this. You can see from the above screenshot, when the second argument is a subset of first argument, "present" was returned, else "notpresent" was returned We can also use bb.utils.contains inside if loop. This we can use inside a recipe. if ${@bb.utils.contains('SOMEFLAG','NEWVALUE3','true','false',d)}; then     FOO = 'HELLO' fi
Read more

make config vs oldconfig vs defconfig vs menuconfig vs savedefconfig

-
Image
Building the Linux Kernel is a two-step process: Configuring the Kernel options Building the Kernel with those options. There are many methods available for configuring the kernel. make config: Text-based Configuration.  Options are prompted one after another. All options need to be answered Access to former options is not possible make menuconfig: Menu-driven user interface Allows to navigate forwards and backward directly between features Allows to load and save files with filenames different from ".config" Provides search feature It uses ncurses library for GUI. If the ncurses library is not installed, make menuconfig option fails. To install ncurses library on Ubuntu: sudo apt-get install libncurses5-dev make defconfig: Creates a ".config" file with default options from the ARCH supplied defconfig Configurations are generally stored in the directory: arch/$(ARCH)/configs $ ls arch/x86/configs/ i386_defconfi...
Read more

PREFERRED_PROVIDER and PREFERRED_VERSION in Yocto

-
Image
When we run "bitbake <target>", bitbake looks at the PROVIDES variable of each recipe to find out the recipe for the particular target. The Default value of PROVIDES is PN. PN --> Name of the Recipe PV --> Version of the Recipe PR --> Revision of the Recipe PREFERRED_PROVIDER: Sometimes a target can have multiple providers. PREFERRED_PROVIDER determines which recipe should be given preference when multiple recipes provide the same item. E.g. virtual/kernel, u-boot will be provided by multiple recipes PREFERRED_PROVIDER_virtual/kernel = "linux-imx" PREFERRED_PROVIDER_u-boot = "uboot-imx" This should be written in local.conf or machine.conf PREFERRED_VERSION: When multiple versions of  a recipe are available, this variable determines which recipe should be given preference. If we don't state the version, bitbake will pick up the highest version. E.g. PREFERRED_VERSION_linux-imx = "3.10.17-1.0.0" PREFERRED_VERSI...
Read more