CODEWITHSUNDEEP
windowsoperating-systemdriverwdm
ratsafalig
ratsafalig

Reputation: 502

How Operation System obtain Hardware ID

I am recently read documentation about Windows-Driver-Model, one of a chapter of it says :

Before a driver is installed for a new device, the bus or hub driver to which the device is connected assigns a hardware identifier (ID) to the device.

But how ??

For example the OS want to communicate with a USB device.

How can it ( the os ) obtain the hardware-id of the device ?

Is there some kind of protocol to communicate with the hardware that works like :

If there is a protocol like this, could you please told me the "standard" of such a protocol.

Upvotes: 0

Views: 190

Answers (1)

user123
user123

Reputation: 2884

On most modern computers every USB hub is connected to one xHCI controller (https://wiki.osdev.org/EXtensible_Host_Controller_Interface). At boot the BIOS will build ACPI tables in RAM that the OS will look for in conventional positions. Once the OS finds these tables, it will look at every entry to determine what devices are plugged to the computer including xHCI controllers. As stated on osdev.org

All xHCI controllers will have a Class ID of 0x0C, a Sublcass ID of 0x03, and an Interface value of 0x30. The configuration space for this device will contain two Base Address Registers: BAR0 and BAR1. These two 32-bit address fields combine to create a single 64-bit address that points to the base address of the memory mapped registers for the controller.

The memory mapped register of the xHCI s are then used to send commands to the USB device including commands to get the device descriptor of the USB device. The document on https://www.intel.com/content/dam/www/public/us/en/documents/technical-specifications/extensible-host-controler-interface-usb-xhci.pdf is the spec for the xHCI. So if you want to really understand how it works under the hood then this is a great place to look at.

Upvotes: 1

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