Linux Driver Development for Embedded Processors

This project contains a subset of the lab modules introduced throughout the Linux Driver Development for Embedded Processors text. The examples in this repo target the Raspberry Pi 3 Model B+. All the labs were built and tested using the rpi-6.1.y kernel.

Checking Out the Project

This project includes the rpi-6.1.y raspberrypi Linux kernel branch as a submodule. There's a lot of code and a lot of git history that comes along with the rpi-6.1.y submodule. To speed up the checkout process and save space on your PC, you may want to follow these steps when cloning the repo:

$ git clone git@github.com:ivan-guerra/eldd.git
$ cd eldd
$ git submodule init
$ git submodule update --depth 1

You can change the argument to --depth to include however much history you like or remove it completey for the full history.

Building and Deploying the Kernel

First, install the kernel dependencies and cross compilation tools required to build the Linux kernel. These are defined in the "Cross Compiling the Kernel" section of the Rapsberry Pi docs.

Build and optionally configure the kernel using the included scripts/kernel_build.sh script. kernel_build.sh will apply the bcm2711_defconfig on first run.

Note You must manually apply the kernel configs described in Chapter 1 pg. 52 for all the lab drivers to function properly!

To deploy your kernel, mount the boot and rootfs partitions of your Pi's SD card:

mount /dev/sdb1 /mnt/fat32
mount /dev/sdb2 /mnt/ext4

Be sure to pick partition and mount point names that make sense for your system!

You can use the scripts/kernel_install.sh script to install the kernel image, dtbs, and modules to the appropriate partitions. The kernel_install.sh script expects two arguments: the boot mount point followed by the rootfs mount point (in that order). For example,

sudo ./kernel_install /mnt/boot /mnt/ext4

Building and Deploying the Labs

You can build all the lab modules by running the scripts/lab_build.sh script. For the build to succeed, you must have successfully followed the instructions in "Building and Deploying the Kernel". Post build, a *.ko kernel module will be present in each lab_<CHAPTER_NUM>_<LAB_NUM>. You can secure copy *.ko modules in bulk from host to RPI using scripts/lab_deploy.sh. See the comments in lab_deploy.sh for more info.

Device Tree Overlays

Throughout the text, the author directly modifies the BCM2711 dts files. You can do the same if you like. Optionally, you can apply the included Device Tree Overlays to achieve the same effect and not litter the original dts files.

Relevant lab overlays are included in overlays/. To apply an overlay, copy the overlay's *.dts file to linux/arch/arm64/boot/dts/overlays and then edit the Makefile to include your overlay.

Follow the instructions in "Building and Deploying the Kernel" to build and install your new overlay to the SD card.

Edit the config.txt in the boot directory of your Pi's SD card to include a dtoverlay entry specifying your new overlay. For example:

dtoverlay=my-overlay

Boot your Pi off the SD card and your new overlay will automatically be applied during boot.

Source Material

The author has made these and many other labs freely availably on his GitHub page. Included in his repo are lab drivers for processors other than the RPI's BCM2837: linux_book_2nd_edition