NAME
pcppi —
PC (ISA) control and timer port
driver
SYNOPSIS
pcppi* at isa?
spkr0 at pcppi?
DESCRIPTION
Thepcppi driver handles resource allocation and device
attachment for the ports related to the ISA speaker in the traditional PC/AT
“design”. These are the “system control port”
(which was implemented by the 8255 “PPI” in the XT, hence the
name of this driver) at I/O address 0x61 and the first 8253 timer at
0x40-0x43.
The pcppi driver provides its child
devices with the ability to output simple tones through the PC speaker. The
speaker(4) device uses this to synthesize sounds. It also provides
helper functions to the pckbd(4) driver as a substitute for a “keyboard
beep”, because the PC keyboard hardware doesn't provide this.