Devhidraw

Devhidraw, more commonly called the hidraw interface in Linux, refers to the set of raw HID device files exposed by the kernel under /dev/hidraw*. These special device nodes provide unprocessed access to HID (Human Interface Device) reports from USB and Bluetooth HID peripherals. Unlike the kernel’s evdev or input event subsystem, hidraw delivers HID reports exactly as they are received, without translation or interpretation by the kernel.

Each hidrawX device corresponds to a HID device recognized by the system. Applications can open these files and read raw input reports or write output/feature reports back to the device, depending on the device’s capabilities. The hidraw interface is commonly used for debugging, reverse engineering, or implementing custom drivers and user-space protocols for HID devices. Typical use cases include logging HID communications, extracting device descriptors, or implementing proprietary communication with specialized hardware.

Access to hidraw devices is controlled by the system’s permissions and groups, reflecting security considerations since raw access bypasses the kernel’s input processing. Programs that interact with hidraw often need elevated privileges or membership in an appropriate group, and care is needed to avoid interfering with devices used by the standard input subsystem.

In practical terms, developers may use tools or libraries that interface with /dev/hidraw*, or use ioctl and read/write calls to manage reports. Hidraw is complemented by higher-level interfaces in Linux, such as the input subsystem for standard keyboard and mouse events, but hidraw remains the avenue for raw, uninterpreted HID data.