The grbeep driver generates beeps on platforms (including Sun Blade
100) that use SMBbus-based registers and USB keyboards. When the KIOCCMD ioctl is issued to the USB keyboard module (see usbkbm(7M)) with command KBD_CMD_BELL/KBD_CMD_NOBELL, usbkbm(7M)
passes the request to the grbeep driver to turn the beep
on and off, respectively.