Kurz: Embedded Linux kernel and driver development

Lektoři kurzu

Lektoři z firmy: ICT Pro s.r.o. – Kurzy, školení, konzultace ICT a Soft Skills

[Kurz] Program kurzu (obsah přednášky/semináře/rekvalifikace/studia) ...

Introduction to the Linux kernel
• Kernel features
• Understanding the development process
• Legal constraints with device drivers
• Kernel user interface (/proc and /sys)
• Userspace device drivers

Kernel sources
• Specifics of Linux kernel development
• Coding standards
• Retrieving Linux kernel sources
• Tour of the Linux kernel sources
• Kernel source code browsers: cscope, Kscope, Linux Cross Reference (LXR)

Lab - Kernel sources
• Making searches in the Linux kernel sources: looking for C definitions, for definitions of kernel configuration parameters, and for other kinds of information
• Using the Unix command line and then kernel source code browsers

Configuring, compiling and booting the Linux kernel
• Kernel configuration
• Native and cross-compilation. Generated files
• Booting the kernel. Kernel booting parameters

Lab - Kernel configuration, cross compiling and booting
• Configuring, cross-compiling and booting a Linux kernel

Linux kernel modules
• Linux device drivers
• A simple module
• Programming constraints
• Loading, unloading modules
• Module dependencies
• Adding sources to the kernel tree

Lab - Writing modules
• Write a kernel module with several capabilities
• Access kernel internals from your module
• Setup the environment to compile it

Linux device model
• Understand how the kernel is designed to support device drivers
• The device model
• Binding devices and drivers
• Platform devices, Device Tree
• Interface in userspace: /sys

Lab - Linux device model for an I2C driver
• Implement a driver that registers as an I2C driver
• Modify the Device Tree to list an I2C device
• Get the driver called when the I2C device is enumerated at boot time

Introduction to the I2C API
• The I2C subsystem of the kernel
• Details about the API provided to kernel drivers to interact with I2C devices

Pin muxing
• Understand the pinctrl framework of the kernel
• Understand how to configure the muxing of pins

Lab - Communicate with the Nunchuk over I2C
• Configure the pin muxing for the I2C bus used to communicate with the Nunchuk
• Extend the I2C driver started in the previous lab to communicate with the Nunchuk via I2C

Kernel frameworks
• Block vs. character devices
• Interaction of userspace applications with the kernel
• Details on character devices, file_operations, ioctl(), etc.
• Exchanging data to/from userspace
• The principle of kernel frameworks

The input subsystem
• Principle of the kernel input subsystem
• API offered to kernel drivers to expose input devices capabilities to userspace application
• Userspace API offered by the input subsystem

Lab - Expose the Nunchuk functionality to userspace
• Extend the Nunchuk driver to expose the Nunchuk features to userspace applications, as a input device.
• Test the operation of the Nunchuk using sample userspace applications

Memory management
• Linux: memory management - Physical and virtual (kernel and user) address spaces
• Linux memory management implementation
• Allocating with kmalloc()
• Allocating by pages
• Allocating with vmalloc()

I/O memory and ports
• I/O register and memory range registration
• I/O register and memory access
• Read / write memory barriers

Minimal platform driver and access to I/O memory
• Implement a minimal platform driver
• Modify the Device Tree to instantiate the new serial port device
• Reserve the I/O memory addresses used by the serial port
• Read device registers and write data to them, to send characters on the serial port

The misc kernel subsystem
• What the misc kernel subsystem is useful for
• API of the misc kernel subsystem, both the kernel side and userspace side

Lab - Output-only serial port driver
• Extend the driver started in the previous lab by registering it into the misc subsystem
• Implement serial port output functionality through the misc subsystem
• Test serial output from userspace

Processes, scheduling, sleeping and interrupts
• Process management in the Linux kernel
• The Linux kernel scheduler and how processes sleep
• Interrupt handling in device drivers: interrupt handler registration and programming, scheduling deferred work

Lab - Sleeping and handling interrupts in a device driver
• Adding read capability to the character driver developed earlier
• Register an interrupt handler
• Waiting for data to be available in the read file operation
• Waking up the code when data is available from the device

Locking
• Issues with concurrent access to resources
• Locking primitives: mutexes, semaphores, spinlocks
• Atomic operations
• Typical locking issues
• Using the lock validator to identify the sources of locking problems

Lab - Locking
• Observe problems due to concurrent accesses to the device
• Add locking to the driver to fix these issues

Driver debugging techniques
• Debugging with printk
• Debugfs entries
• Analyzing a kernel oops
• Using kgdb, a kernel debugger
• Using the Magic SysRq commands
• Debugging through a JTAG probe

Lab - Investigating kernel faults
• Studying a broken driver
• Analyzing a kernel fault and locating the problem in the source code

ARM board support and SoC support
• Understand the organization of the ARM support code
• Understand how the kernel can be ported to a new hardware board

Power management
• Overview of the power management features of the kernel
• Topics covered: clocks, suspend and resume, dynamic frequency scaling, saving power during idle, runtime power management, regulators, etc.

The Linux kernel development process
• Organization of the kernel community
• The release schedule and process: release candidates, stable releases, long-term support, etc.
• Legal aspects, licensing
• How to submit patches to contribute code to the community

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