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.Dd March 5, 1998
.Dt PPC 4
.Os FreeBSD
.Sh NAME
.Nm ppc
.Nd
Parallel port chipset driver
.Sh SYNOPSIS
.Cd "controller ppc0 at isa? port? tty irq 7"
.Pp
For one or more PPBUS busses:
.Cd "controller ppbus at ppc0"
.Sh DESCRIPTION
The
.Em ppc
driver provides low level support to various parallel port chipsets for the
.Xr ppbus 4
system.
.Pp
During the probe phasis, ppc detects parallel port chipsets and initialize
private data according to their operating mode: COMPATIBLE,
NIBBLE, PS/2, EPP, ECP and other mixed modes. If a mode is provided at startup
throw the flags variable of the boot interface, the operating mode of the
chipset is forced according to 'flags' and its available modes.
.Pp
During attach phasis, ppc allocates a ppbus structure, initializes it and
calls ppbus attach function.
.Ss Supported flags
.Bl -item -offset indent
.It
bits 0-3: chipset forced mode(s)
.Bd -literal
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 */
.Ed
.Pp
And any mixed values.
.It
bit 4: EPP protocol (0 EPP 1.9, 1 EPP 1.7)
.It
bit 5: activate IRQ (1 IRQ disabled, 0 IRQ enabled)
.It
bit 6: disable chipset specific detection
.El
.Ss Supported chipsets
Some parallel port chipsets are explicitly supported by ppc: detection and
initialisation code has been written according to specs datasheets.
.Bl -bullet -offset indent
.It
SMC FDC37C665GT and FDC37C666GT chipsets
.It
Natsemi PC873xx-family (PC87332 and PC87306)
.It
Winbond W83877xx-family (W83877F and W83877AF)
.It
SMC-like chipsets with mixed modes (see
.Xr ppbus 4 )
.El
.Ss Adding support to a new chipset
You may want to add support for the newest chipset your last motherboard was
sold with? For the ISA bus, just retrieve the specs of the chipset and
write the corresponding
.Fn ppc_mychipset_detect ""
function.
Then add an entry to the general purpose
.Fn ppc_detect ""
function. 
.Pp
Your
.Fn ppc_mychipset_detect ""
function should ensure that: if the mode field of the
.Va 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
.Sh SEE ALSO
.Xr ppbus 4
.Sh BUGS
The chipset detection process may corrupt your chipset configuration. You may
disable chipset specific detection by using the above flags.
.Sh HISTORY
The
.Nm
manual page first appeared in
.Fx 3.0 .
.Sh AUTHOR
This
manual page was written by
.An Nicolas Souchu .