What does platform mean in linux?

In Linux, platform is a virtual bus, corresponding to real buses such as "spi/sdio/usb/pcie"; platform can separate hardware and software, and the resources described by platform have one thing in common The address is taken directly on the CPU bus. The platform device will be assigned a name and a series of resources such as addresses and interrupt request numbers.

#The operating environment of this tutorial: linux7.3 system, Dell G3 computer.

What does platform mean in Linux

platform is a virtual bus, which corresponds to the real spi/sdio/usb/pcie and other buses

Logical bus An important function of is to discover the device and find the appropriate driver to operate the device.

The platform bus is a virtual logical bus that meets the logical interconnection function. In order to uniformly manage devices, the platform can use the platform bus to uniformly manage a type of device that does not physically have a bus.

Common buses such as USB, SPI, UART, PCI, I2S and other buses are physically real buses. The Linux system has designed a method for unified management of such buses, namely bus. At the same time, the platform bus is also designed for devices that do not physically have a bus. Therefore, the Linux kernel designers designed the platform bus. In other words, the plarform bus is designed for devices that have no physical bus inside the SoC. It They all belong to the bus category.

The advantage of this is that the writer of the device (device) side code only cares about the specific hardware part, and the common part of the device (the stable part) is completed by the kernel designer, which reduces the driver Difficulty of writing.

Through the platform bus, device attributes (also called data) and drivers can be separated, so that the same driver can be used to support different devices with the same functional core hardware. This avoids the phenomenon that one device requires one driver and reduces repetitive work.

Extended knowledge

platform platform bus related definitions

platform platform bus related objects are defined in the file drivers/base/platform.c middle. This file implements the platform bus object and object operation methods.

Two important data structures

1. platform_driver

This is a structure object embedded with a device_driver, which defines the method of operating the object.

2. platform_device

It is an embedded device structure object, which defines the attributes of the device description resource.

The specific object definition is as follows:

1. platform_driver object definition

struct platform_driver 
{
int (*probe)(struct platform_device *);     //探测函数，安装设备，初始化设备，并且判断是否能成功（初始化成功，通讯成功等等）
int (*remove)(struct platform_device *);    //从内核中删除这个设备
void (*shutdown)(struct platform_device *); // 关闭设备
int (*suspend)(struct platform_device *, pm_message_t state);  //挂起
int (*resume)(struct platform_device *);    //唤醒
struct device_driver driver;          //驱动的通用属性
const struct platform_device_id *id_table; //设备ＩＤ表
};

platform_device object pair definition:

struct platform_device 
{
const char* name;  　　　　//平台总线中设备的名字,在平台总线下有多个设备，每个设备都有自己的名称
intid;         　　　　 //设备的排序
struct devicedev; 　　　　//所有设备通用的属性
u32num_resources; 　　　//设备资源，如IO等一些外设等的个数
struct resource* resource; //设备资源的首地址，和上面的个数num_resources一起构成一个数组来表示这个资源
const struct platform_device_id*id_entry;  //设备ＩＤ表，表示同一种类型的几个设备的ＩＤ号，数组表示。
struct pdev_archdataarchdata;　/* arch specific additions *///用户自定义数据，扩展数据
};

Register platform bus driver function:

int platform_driver_register(struct platform_driver *drv)

Function to register platform bus device:

int platform_device_register(struct platform_device *pdev)

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