Lab 2: Userspace Drivers

Table of Contents

In this lab you will create user space drivers for the buttons, switches, and interrupt controller on the hardware system.

Objectives

  • Implement user space drivers for an embeddeded Linux system.
  • Learn how to use the Linux UIO driver to access hardware from user space.
  • Learn how to control GPIO and Interrupt Controller IP cores with registers.

Preliminary

Software Stack

Review the Software Stack that illustrates how the different software modules you will create in this class will work together. This will be discussed more in class.

Make note of the provided system.h file.

The Hardware System

For this lab, the complete hardware system will be provided; you shouldn’t make any changes to the hardware. You should review the hardware system before you start coding the lab. Particularly look for the GPIO modules that interface with the buttons and switches, and look at how the interrupt lines are connected to the Interrupt Controller.

AXI GPIO Module

You will need to write drivers for the buttons and switches. Both of these are connected to the hardware using an AXI GPIO module. Read the AXI GPIO documentation (link on the hardware system page).

Note: The GPIO_TRI register was not generated for the buttons and switches GPIO blocks. If you try to read the GPIO_TRI register, you will get nonsense. Also, it makes no sense to write this register as it does not exist.

AXI Interrupt Controller

You will need to write a driver for the AXI Interrupt Controller. Read the documentation (link on the hardware system page).

UIO

The drivers you write in this lab will run in user space; however, from user space, you are not permitted to interact directly with hardware devices. As shown on the Software Stack page, there is a lightweight kernel driver for the GPIO modules and Interrupt Controller, called the Userspace I/O (UIO) driver. This provides a bridge that allows you to access these devices from user space. You will need to read about the UIO.

Make sure you read the entire hardware system page, including the text at the bottom that discussed how the UIO driver is used for the different pieces of hardware in this lab.

Implementation

  1. Implement a driver for the buttons.
    • buttons.h is provided to you.
    • The drivers folder contains CMakeLists.txt that you can uncomment line by line when you are ready to compile your drivers.
    • A buttons_test application is provided to you. You will need to uncomment the appropriate line from the app folder’s CMakeLists.txt to compile it.
  2. Implement a driver for the switches.
    • Since the switches use the same GPIO module as the buttons, this driver will be nearly identical to the buttons driver.
    • You are given switches.h and a switches_test application.
  3. Implement a driver for the AXI Interrupt Controller.
    • intc.h is provided to you.
    • A interrupt_test application is provided to you. You can use this to test the basic functionality of your interrupt controller driver, and the interrupt API for your buttons and switches drivers. This test application is provided to you for convenience; just because it works it does not guarantee your drivers are bug free. You may want to further enhance the provided test applications.
    • Another test is provided, the intr_rate application, to further test the interrupt controller driver. If your driver is correct, this application should correctly report the rate at which interrupts are being generated by the FIT (every 16.67ms). You can change the flag on this line if you want to test your intc_pending_nonblocking() function.

When you are graded we will run each of the test applications and verify that they work as expected. So while you may change the test applications somewhat to help you debug your drivers, please do not commit any modifications to these test applications that change their behavior, or would cause them to not work when we run them.

Submission

Follow the instructions on the Submission page.