PID (Product ID) and VID (Vendor ID) are distinct but co-dependent 16-bit identification numbers crucial for a host system to recognize and interact with connected hardware devices, such as USB peripherals. A VID is a 16-bit vendor number (Vendor ID), uniquely identifying the manufacturer of a device. Concurrently, a PID is a 16-bit product number (Product ID), which specifically identifies a particular product model from that vendor. Together, a host uses the VID/PID combination to find the drivers (if any) that are to be used for the USB device, enabling proper communication and functionality.
Understanding Vendor ID (VID)
The Vendor ID (VID) is a fundamental identifier that signifies the manufacturer of a hardware device.
- Definition: It is a 16-bit vendor number. This means it's a unique hexadecimal value (e.g.,
0x046dfor Logitech,0x8086for Intel) assigned to each company that produces devices requiring such identification. - Assignment: For USB devices, VIDs are centrally assigned and managed by the USB Implementers Forum (USB-IF), ensuring global uniqueness among vendors. This prevents conflicts where multiple manufacturers might accidentally use the same identifier.
- Purpose: The VID acts like a "company registration number" for hardware, allowing operating systems to identify the originating manufacturer of a connected device.
Understanding Product ID (PID)
The Product ID (PID) works in tandem with the VID to pinpoint the exact model of a device.
- Definition: It is a 16-bit product number. This identifier is unique within the scope of a single vendor's products.
- Assignment: Unlike VIDs, PIDs are assigned by the vendor (manufacturer) themselves. Each specific product model they create will have its own distinct PID.
- Purpose: The PID differentiates various devices produced by the same manufacturer. For example, Logitech (VID) might have one PID for a keyboard and another PID for a mouse.
The Synergy: VID/PID Combination
The true power of PID and VID lies in their combined usage. When you plug a USB device into your computer, the host system performs the following critical steps:
- Device Enumeration: The host queries the newly connected device to obtain its VID and PID.
- Driver Matching: The host then uses this unique VID/PID combination to search its internal database or registered drivers. It looks for a driver package that explicitly lists support for that specific pair of identifiers.
- Driver Loading: If a match is found, the operating system loads the appropriate driver, allowing the device to function correctly without manual intervention. This is how the "Plug-and-Play" experience is achieved.
For instance, a USB mouse from "Company X" might have a VID of 0xABCD and a PID of 0x1234. When connected, your computer uses 0xABCD:0x1234 to find the correct driver for that specific mouse model.
Key Characteristics of PID and VID
To further clarify their roles, here's a comparative overview:
| Feature | Vendor ID (VID) | Product ID (PID) |
|---|---|---|
| Definition | A 16-bit vendor number | A 16-bit product number |
| Assigned By | Central authority (e.g., USB Implementers Forum) | The device vendor/manufacturer itself |
| Identifies | The manufacturer/company of the device | A specific product model from that manufacturer |
| Uniqueness | Globally unique for each manufacturer | Unique only within a single vendor's range of products |
| Primary Role | Identifies who made the device | Identifies what specific device it is |
| Usage Context | Always combined with a PID for full identification | Always combined with a VID for full identification |
Why are PID and VID Crucial?
These seemingly simple numbers are foundational for modern computing and device interaction due to several key reasons:
- Automatic Device Recognition: They enable operating systems to instantly identify what type of device has been connected without user input.
- Seamless Driver Loading: The VID/PID pair is the primary mechanism for the host to automatically locate and load the correct software drivers, ensuring the device works out of the box (Plug-and-Play).
- System Stability: By ensuring the correct driver is loaded, VID/PID combinations help maintain system stability and prevent conflicts.
- Troubleshooting: When devices don't work, checking their VID/PID can help diagnose issues, find manual drivers, or identify counterfeit products.
- Firmware Updates: Many firmware update tools require a specific VID/PID to ensure the update is applied to the correct device model.
- Security Policies: In corporate or industrial environments, VID/PID can be used to whitelist or blacklist specific devices, enhancing security.
Practical Insights and Examples
- Operating System Integration: In Windows, you can find the VID and PID of a device in the Device Manager under the device's properties (Details tab, Hardware IDs property). On Linux, the
lsusbcommand often displays VID:PID pairs for connected USB devices. - Driver Development: Hardware manufacturers develop drivers specifically designed to respond to their unique VID/PID combination, ensuring compatibility and functionality.
- Third-Party Drivers: Sometimes, generic drivers or open-source projects might use a range of PIDs for a specific VID to support multiple similar devices from one vendor.
