Training Linux Drivers: Writing Linux Drivers

D3Linux Drivers
Writing Linux Drivers
Objectives
  • Mastering kernel development and debug tools
  • Discovering multi-core programming in the Linux kernel
  • Programming IOs, interrupts, timers and DMA
  • Installing and integrating drivers inside Linux kernel
  • Managing synchronous and asynchronous IOs and ioctl
  • Writing a complete character driver
  • Understanding specificities of 2.6 and 3.x versions
  • Mastering kernel debugging technics with Lauterbach JTAG probes.
Labs are conducted on target boards, that can be:
    Dual Cortex/A7-based "STM32MP15-DISCO" boards from STMicroelectronics.
    Quad Cortex/A9-based "SabreLite" boards from NXP.
    Quad Cortex/A53-based "imx8q-evk" boards from NXP.
We use a recent (4.x) linux kernel, as supported by the chip supplier.
  • This course is for engineers that install Linux on a custom platform and have to create specific device drivers.
  • Theoretical course
    • PDF course material (in English) supplemented by a printed version.
    • The trainer answers trainees' questions during the training and provide technical and pedagogical assistance.
  • Practical activities
    • Practical activities represent from 40% to 50% of course duration.
    • Code examples, exercises and solutions
    • One PC (Linux ou Windows) for the practical activities with, if appropriate, a target board.
      • One PC for two trainees when there are more than 6 trainees.
    • For onsite trainings:
      • An installation and test manual is provided to allow preinstallation of the needed software.
      • The trainer come with target boards if needed during the practical activities (and bring them back at the end of the course).
  • Downloadable preconfigured virtual machine for post-course practical activities
  • At the start of each session the trainer will interact with the trainees to ensure the course fits their expectations and correct if needed
  • The prerequisites indicated above are assessed before the training by the technical supervision of the traineein his company, or by the trainee himself in the exceptional case of an individual trainee.
  • Trainee progress is assessed in two different ways, depending on the course:
    • For courses lending themselves to practical exercises, the results of the exercises are checked by the trainer while, if necessary, helping trainees to carry them out by providing additional details.
    • Quizzes are offered at the end of sections that do not include practical exercises to verifythat the trainees have assimilated the points presented
  • At the end of the training, each trainee receives a certificate attesting that they have successfully completed the course.
    • In the event of a problem, discovered during the course, due to a lack of prerequisites by the trainee a different or additional training is offered to them, generally to reinforce their prerequisites,in agreement with their company manager if applicable.

Course Outline

  • Development in the Linux kernel
  • Memory allocation
  • Linked lists
Exercise:  Writing the "hello world" kernel module
Exercise:  Adding a driver to kernel sources and configuration menu
Exercise:  Using module parameters
Exercise:  Writing interdependent modules using memory allocations, reference counting and linked lists
  • The /proc and debugfs filesystems
  • Traces
  • The kernel Dynamic Debugging interface
  • The Kernel Address Sanitizer
  • Debugging memory problems with kmemleak
  • Using the Undefined Behavior Sanitizer
  • Code coverage using gcov
  • Debugging with kgdb
  • Debugging with a JTAG probe
Exercise:  Display dynamic traces on the running kernel
Exercise:  Debug a module initialization using kgdb
  • Task handling
  • Concurrent programming
  • Timers
  • Kernel threads
Exercise:  Fixing race conditions in the previous lab with mutexes
  • Accessing the device driver from user space
  • Driver registration
Exercise:  Step by step implementation of a character driver:
•  driver registration (major/minor reservation) and device special file creation (/dev)
  • Kernel structures used by drivers
  • Opening and closing devices
  • Data transfers
  • Controlling the device
  • Mapping device memory
Exercise:  Step by step implementation of a character driver:
•  Implementing open and release
•  Implementing read and write
•  Implementing ioctl
•  Implementing mmap
  • Task synchronization
  • Synchronous request
  • Asynchronous requests
Exercise:  implementation of a pipe-like driver:
•  implementing waiting and waking
•  adding non-blocking, asynchronous and multiplexed operations (O_NONBLOCK, SIGIO, poll/select)
  • Memory-mapped registers
  • Interrupts
  • Gpios
  • User-level access through /sys or the GPIO character driver
Exercise:  Polling gpio driver with raw register access
Exercise:  Interrupt-based gpio driver with raw register access
Exercise:  gpio driver using the gpiolib
  • Plug-and-Play management
  • Static devices declaration
    • in the BSP code
    • in the device tree
  • Platform bus
  • PCI
  • SPI
  • Power management
    • System sleep
    • Implementing power management in drivers
    • Remote wakeup
Exercise:  Implementing a platform driver and customizing the device tree to associate it to its device (a serial port)
Exercise:  Implementing power management in the previous driver
Exercise:  Implementing remote wakeup in the previous driver
  • Linux Driver Model Architecture
    • Overview
    • Classes
    • Busses
  • Hot plug management
    • Plugging devices
    • Removing devices
  • Writing udev rules
Exercise:  Writing a custom class driver
Exercise:  Writing a misc driver
  • Direct Memory Access
    • DMA scenarios
    • Buffer access
  • DMA programming
    • Bus master DMA
    • Slave DMA
  • Memory barriers
Exercise:  Implementing slave DMA in a serial port driver
  • The USB bus
  • USB devices
  • User-space USB interface
  • USB descriptors
  • USB requests
  • USB device drivers
Exercise:  Writing a USB host driver
  • structures
    • network interface representation (struct net_device)
    • network packet (struct sk_buff)
  • scatter/gather
  • interface
    • receiving packets
    • sending packets
    • lost packets management
    • network interface statistics
  • New network API (NAPI)
    • "interrupt mitigation" (suppression of unneeded IRQs)
    • "packet throttling" (suppression of packets in the driver itself when system is overwhelmed)
  • Virtual Memory
  • Memory Allocation
    • Free page management
    • Normal memory allocation
    • Virtual memory allocation
    • Huge allocations
Duration
4 days
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Last update of course schedule: 15 November 2022

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