Linux device drivers development john pdf download

To help you master this complex domain, Apriorit driver development experts created this tutorial. The Linux kernel is written in the C and Assembler programming languages. C implements the main part of the kernel, while Assembler implements architecture-dependent parts. A module is a specifically designed object file. When working with modules, Linux links them to the kernel by loading them to the kernel address space.

Module code has to operate in the kernel context. This requires a developer to be very attentive. If a developer makes a mistake when implementing a user-level application, it will not cause problems outside the user application in most cases. But mistakes in the implementation of a kernel module will lead to system-level issues. Luckily for us, the Linux kernel is resistant to non-critical errors in module code.

When the kernel encounters such errors for example, null pointer dereferencing , it displays the oops message — an indicator of insignificant malfunctions during Linux operation.

After that, the malfunctioning module is unloaded, allowing the kernel and other modules to work as usual. In addition, you can analyze logs that precisely describe non-critical errors. Keep in mind that continuing driver execution after an oops message may lead to instability and kernel panic. The kernel and its modules represent a single program module and use a single global namespace. Exported global characters must have unique names and be cut to the bare minimum.

We can do that with the following code:. This function has no effect if the driver is statically compiled into the kernel. Now our simple module is complete. These operations will be useful for Linux kernel driver development. They facilitate interactions between the user space and the kernel code. To make the kernel receive anything, you can just write it to a device file to pass it to the module serving this file. We can define these numbers in the driver code, or they can be allocated dynamically.

In case a number defined as a constant has already been used, the system will return an error. When a number is allocated dynamically, the function reserves that number to prevent other device files from using the same number.

Here, we specify the name and the major number of a device to register it. If we assign 0 to the major parameter, the function will allocate a major device number on its own.

If the value returned is 0, this indicates success, while a negative number indicates an error. Both device numbers are specified in the 0— range. The device name is a string value of the name parameter. This string can pass the name of a module if it registers a single device. A pointer to an unimplemented function can simply be set to 0. After that, the system will take care of implementing the function and make it behave normally.

To register a device file, we use the following code:. When the lifetime of the driver expires, this global variable will be used to revoke the registration of the device file. This is the only difference between the printk function and the printf library function. The printk function forms a string, which we add to the circular buffer. From there the klog daemon reads it and sends it to the system log. Implementing the printk allows us to call this function from any point in the kernel.

Use this function carefully, as it may cause overflow of the circular buffer, meaning the oldest message will not be logged. The book also offers a practical approach on direct memory access and network device drivers. By the end of this book, you will be comfortable with the concept of device driver development and will be in a position to write any device driver from scratch using the latest kernel version v4.

Downloading the example code for this book. Download Example Code. About This Book Over 79 hands-on recipes for professional embedded Linux developers to optimize and boost …. Learn algorithms for solving classic computer science problems with this concise guide covering everything from fundamental ….

Leverage the power of Linux to develop captivating and powerful embedded Linux projects About This Book …. Get up and running with system programming concepts in Linux Key Features Acquire insight on Linux …. Skip to main content. Start your free trial. Book description Learn to develop customized device drivers for your embedded Linux system About This Book Learn to develop customized Linux device drivers Learn the core concepts of device drivers such as memory management, kernel caching, advanced IRQ management, and so on.

Practical experience on the embedded side of Linux Who This Book Is For This book will help anyone who wants to get started with developing their own Linux device drivers for embedded systems.