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The hid driver is a USBA (Solaris USB Architecture) compliant client driver that supports the Human Interface Device Class (HID) 1.0 specification. The Human Interface Device (HID) class encompasses devices controlled by humans
to operate computer systems. Typical examples of HID devices include keyboards, mice, trackballs, and joysticks. HID also covers front-panel controls such as knobs, switches, and buttons. A USB device with multiple interfaces may have one interface for audio and a HID interface to define the buttons
that control the audio.
The hid driver is general and primarily handles the USB functionality of the device and generic HID functionality. For example, HID interfaces are required to have an interrupt pipe for the device to send data packets, and the hid driver opens the pipe to
the interrupt endpoint and starts polling. The hid driver is also responsible for managing the device through the default control pipe. In addition to being a USB client driver, the hid driver is also a STREAMS driver so that modules may be pushed on top of it.
The HID specification is flexible, and HID devices dynamically describe their packets and other parameters through a HID report descriptor. The HID parser is a misc module that parses the HID report descriptor and creates a database of information about the device. The hid driver
queries the HID parser to find out the type and characteristics of the HID device. The HID specification predefines packet formats for the boot protocol keyboard and mouse.
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