Operating system through a variety of drivers rely on home and hardware devices, it has shielded a variety of devices for users, drive hardware is the most basic function of the operating system, and provide a unified operation. Device drivers are one of the most basic components of the operating system and are more than 60% in the Linux kernel source program, so familiarity with driver writing is important.
The Linux system maps each driver into a single file. These files are referred to as device files or driver files and are present in the/dev directory. Thus, in the application's view, the hardware device is just a device file, and the application can operate the hardware device as if it were a normal file, which greatly facilitates the processing of the device.
Steps to write a driver:
(1) Build Linux driver skeleton (load and unload Linux drivers) any type of program has a basic structure, and Linux drivers are no exception. The Linux kernel needs to load the driver first when it uses the driver. Some initialization work is also required during the loading process.
(2) Registration and cancellation of equipment files
Any Linux driver requires a device file, or the application will not be able to interact with the driver.
(3) Specify driver-related information
The driver is self-describing.
(4) Specifying a callback function
A driver does not necessarily specify all of the callback functions.
(5) Writing business logic
(6) Writing makefile files
(7) Writing Linux drivers
(8) Installing and uninstalling Linux drivers
1. Preparatory work
Create a directory to store Linux drivers
Create a drive source code file
Write a Makefile file
2. Writing the skeleton of the Linux driver (Initialize and exit drivers)
Installing Linux Drivers
See if Word_count is installed successfully
Uninstalling Linux Drivers
View log information from the driver output
3. Specify driver-related information
Module author, module description, module nickname, open Source protocol
4. Registering and unregistering device files
5. Specifying a callback function
6. Algorithm to achieve statistical word count
7. Compiling, installing, and uninstalling Linux drivers
Testing Linux Drivers
Using the Ubuntu Linux test
Test via OST (native) C program on Android simulator
Using the Android NDK test
Directly manipulate device file testing using Java code
Test with the s3c6410 Development Board
Compiling the driver into the Linux kernel for testing
Develop and test Linux drivers with eclipse
1. Building C Project
2. Establish C source code file connection
3. Setting the Include path
4. Compiling Linux Drivers
Testing Linux drivers in eclipse
1. Import the test_word_count.c file
2. Setting the Include path
3. Establish Targe
4.build Engineering
5. Run the test program
It is important to note that the user space and kernel space to complete the same or similar functions, macros and other resources names are not necessarily the same, some names like: malloc and Kmalloc, some different such as: Atoi and Simple_strol, etc. home.cnblogs.com/u/zivjeli/
Android Deep Exploration (Vol. 1) HAL and Driver Development Sixth Chapter summary
