Android Deep Exploration chapter I

The first chapter of Android Deep Exploration of HAL and Driver Development studied Android system porting and system development in detail.

As the introduction to the book says,Android has become the boss of the current smartphone operating system. So its importance is conceivable, its significance of learning is unusual. Its rapid development depends to a large extent on the ability of anyone to customize their own embedded system with Android's source code, without having to pay Google . And because android native code does not support a lot of devices, in order to perfectly run Android on your device (including mobile phones, smart TVs, tablets, etc.) , youneed some other development program, Allows android to represent the device's hardware (display, Bluetooth, audio, etc.). The process of customizing Android for a specific device is called "porting." At the same time, the most common development in the porting process is Linux drivers that support a variety of hardware devices . And the first one is the first door to the learning drive.

First,Androidsystem architecture, including four-tier architecture, the first layer isLinuxkernel, which is associated with otherLinuxthe core parts of the system differ very little. This layer mainly includesLinuxdrivers and programs for memory management, process management, power management, and more. The second level isC + +code base, this layer mainly includes the use ofC + +the code base that is written, also includesDALIVKWhen the virtual runtime is running (Runtime). The third layer isAndroid SDK API, this layer is usedJavawrite a variety ofLibrary. The fourth layer is the application layer, and this layer is allAndroidusers are exposed, so this layer is equivalent toAndroidof theUI, all theAndroidapplications belong to this layer, and this layer relies on the third time to complete various functions.

the main tasks of Android transplantation are system porting and application porting. In addition to porting Linux drivers, An additional layer of hardware abstraction is added to the Android system. Porting the work if the Android system to be ported provides the driver source code, it is very simple, and vice versa will be more troublesome.

There are three main versions of the Linux kernel that can be identified in two ways. The version number consists of a major version number, a minor version number, a revision number, a fine-tuning version number, and a special description. Because the kernel version update faster, want to learn Linux Drive development, not only need to master reliable knowledge, but also should continue to learn continuous efforts.

Linux device drivers are divided into character devices, block devices, and network devices.

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Android Deep Exploration chapter I