Andriod Deep Exploration of-hal and Driver Development Chapter Seventh reading notes

Creating LED-driven device files

1th Step: Initialize the Cdev with the Cdev_init function

2nd step: Specify the device number. Assign directly in code or dynamically

3rd Step: Use the Cdev_add function to add the character device to the character device array in the kernel

4th step: Create a struct class using the Class_create macro

5th step: Create a device file using the Device_create function

Uninstalling LED-driven device files

You need to call the Device_destroy, Class_destroy, and Unregister_chrdev_region methods in turn

void Device_destroy (struct class *class, dev_t devt)

void Class_destroy (struct class *cls)

void Unregister_chrdev_region (dev_t from, unsigned count)

Control LED

LED drivers can control LEDs in two different ways:

1. Control the LEDs via a string.

2. Control the LEDs with the I/O command.

To control LEDs, use both of these methods. The LED driver must receive the corresponding data. If the LED is controlled by a string. You need to use the File_operations.write function. If the LEDs are controlled through the I/O command, you need to use the FILE_OPERATIONS.IOCTL function.

Porting Linux drivers is a very important one. is to modify the Linux driver source code, you should try not to modify the Linux driver interface.

This chapter focuses on LED drivers, a Linux driver that really deals with hardware. Although the LED driver is not complicated, it only controls a few LEDs, but the LED driver already includes all the necessary parts of the Linux drive. A complete Linux driver consists of two parts: internal processing and hardware interaction. The internal processing mainly refers to the Linux driver loading, unloading, and device file-related action processing (read and write device files, send I/O commands to the device file), as well as business logic. The porting of Linux drivers on different platforms is also handled in these two parts.

Andriod Deep Exploration of-hal and Driver Development Chapter Seventh reading notes