PPC(4)

NAME
ppc - Parallel Port Chipset driver

SYNOPSIS
device ppc0 at isa? port? flags 0xXX irq 7

For one or more PPBUS busses:
device ppbus at ppc0

DESCRIPTION
The ppc driver provides low level support to various parallel port chipsets for the ppbus(4) system.

During the probe phase, ppc detects parallel port chipsets and initializes private data according to their operating mode: COMPATIBLE, NIBBLE, PS/2, EPP, ECP and other mixed modes. If a mode is provided at startup through the flags variable of the boot interface, the operating mode of the chipset is forced according to flags and the hardware supported modes.

During the attach phase, ppc allocates a ppbus structure, initializes it and calls the ppbus attach function.

  Supported flags

bits 0-3: chipset forced mode(s)

    PPB_COMPATIBLE  0x0     /* Centronics compatible mode */
    PPB_NIBBLE      0x1     /* reverse 4 bit mode */
    PPB_PS2         0x2     /* PS/2 byte mode */
    PPB_EPP         0x4     /* EPP mode, 32 bit */
    PPB_ECP         0x8     /* ECP mode */

And any mixed values.

bit 4: EPP protocol (0 EPP 1.9, 1 EPP 1.7)

bit 5: activate IRQ (1 IRQ disabled, 0 IRQ enabled)

bit 6: disable chipset specific detection

bit 7: disable FIFO detection

  Supported chipsets
Some parallel port chipsets are explicitly supported: detection and initialisation code has been written according to their datasheets.

•   SMC FDC37C665GT and FDC37C666GT chipsets

•   Natsemi PC873xx-family (PC87332 and PC87306)

•   Winbond W83877xx-family (W83877F and W83877AF)

•   SMC-like chipsets with mixed modes (see ppbus(4))

  Adding support to a new chipset
You may want to add support for the newest chipset your motherboard was sold with. For the ISA bus, just retrieve the specs of the chipset and write the corresponding ppc_mychipset_detect() function. Then add an entry to the general purpose ppc_detect() function.

Your ppc_mychipset_detect() function should ensure that if the mode field of the flags boot variable is not null, then the operating mode is forced to the given mode and no other mode is available and ppb->ppb_avm field contains the available modes of the chipset.

SEE ALSO
ppbus(4), ppi(4)

HISTORY
The ppc manual page first appeared in FreeBSD 3.0.

AUTHORS
This manual page was written by Nicolas Souchu.

BUGS
The chipset detection process may corrupt your chipset configuration. You may disable chipset specific detection by using the above flags.