Learning Vedon Video Experience (ii)

Learning Vedon Video Experience (ii)

1. character device driver

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Figure 2.7 LCD Hardware Framework

The character device is the most basic device driver in a Linux device and is the cornerstone of other large drives. Character Set

The driver model, as shown in 2.8.

Linux Kernel driver modules are usually composed of module loading function, module unloading function, module license declaration and so on. In the character device driver, register the main device in the module load function, register the operation method, create the device node and so on. Character device driver porting steps:

(1) Create the device file in the module load function, register the main device number, register the operation method

(2) implement their respective operation methods separately

Linux Kernel driver modules are usually composed of module loading function, module unloading function, module license declaration and so on. Registers the master device in the module load function in the character device driver, registers the operation method, creates

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Figure 2.8 Character Device frame diagram

operations such as device nodes. Character device driver porting steps:

(1) Create the device file in the module load function, register the main device number, register the operation method

(2) implement their respective operation methods separately

2. platform Device Drive mechanism

(8)

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Figure 2.9 Character device frame diagram

struct platform_device platform device structure, a platform device corresponding to an actual physical device, the most important thing in the actual device is the hardware information of the physical device, such as: Register address, interrupt number, etc. In linux void  * platform_register_device () Register the platform device structure into the platform device chain list. As shown in 2.9.

    struct Platform_driver platform-driven structure, A platform driver corresponds to a driver, the function interface platform_regisister_driver () Span style= "FONT-SIZE:16PX;" > Register the device driver in the device driver chain list. When the driver or platform device registers the corresponding linked list is constantly querying each other's linked list through struct platform_mach_id probe probe

Compared with the ordinary character device, the platform device driving mechanism separates the device resources from the drive, which makes the drive migration more convenient and convenient. But at the same time, because in order to make the driver universality and the portability characteristic, in the Linux kernel is often divides into the multilayer structure, several files, in the driving internal relations are intricate, the function call relation is very complex, the Linux drive and the kernel seamless.

In Linux device drivers tend to use layered thinking, so that the code has a high interoperability, in large-scale drive, multi-layered structure, the relationship is complex, while the Linux device driven by the idea of object-oriented, using a large number of structures, including the relationship is very complex. As shown in 2.10.

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through the above-mentioned layered thought, it achieves the function of code interoperability, and draws on the object-oriented thought.

Learning Vedon Video Experience (ii)