.\"     $NetBSD: mca.9,v 1.12 2017/07/03 21:28:48 wiz Exp $
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.\" Copyright (c) 2001 The NetBSD Foundation, Inc.
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.\" This code is derived from software contributed to The NetBSD Foundation
.\" by Gregory McGarry.
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.Dd October 7, 2001
.Dt MCA 9
.Os
.Sh NAME
.Nm MCA ,
.Nm mca_intr_establish ,
.Nm mca_intr_disestablish ,
.Nm mca_intr_evcnt ,
.Nm mca_conf_read ,
.Nm mca_conf_write
.Nd MicroChannel Architecture bus
.Sh SYNOPSIS
.In sys/bus.h
.In dev/mca/mcavar.h
.In dev/mca/mcadevs.h
.Ft void *
.Fn mca_intr_establish "mca_chipset_tag_t mc" "mca_intr_handle_t hdl" \
"int level" "int (*handler)(void *)" "void *arg"
.Ft void
.Fn mca_intr_disestablish "mca_chipset_tag_t mc" "mca_intr_handle_t hdl"
.Ft const struct evcnt *
.Fn mca_intr_evcnt "mca_chipset_tag_t mc" "mca_intr_handle_t hdl"
.Ft int
.Fn mca_conf_read "mca_chipset_tag_t mc" "int slot" "int reg"
.Ft void
.Fn mca_conf_write "mca_chipset_tag_t mc" "int slot" "int reg" \
"int data"
.Sh DESCRIPTION
The
.Nm
device provides support for IBM's MicroChannel Architecture bus found
on IBM PS/2 systems and selected workstations.
It was designed as a replacement bus for the ISA bus found on IBM's
older machines.
However, the bus specifications were only available under license, so
MCA did not achieve widespread acceptance in the industry.
.Pp
Being a replacement for the ISA bus, the MCA bus does share some
similar aspects with the ISA bus.
Some MCA devices can be detected via the usual ISA-style probing.
However, most device detection is done through the Programmable Option
Select (POS) registers.
These registers provide a window into a device to determine device-specific
properties and configuration.
The configuration of devices and their POS registers is performed using
IBM's system configuration software.
.Pp
The MCA bus uses level-triggered interrupts while the ISA bus uses
edge-triggered interrupts.
Level triggered interrupts have the advantage that they can be shared
among multiple device.
Therefore, most MCA-specific devices should be coded with shared
interrupts in mind.
.Sh DATA TYPES
Drivers for devices attached to the MCA bus will make use of the
following data types:
.Bl -tag -width compact
.It Fa mca_chipset_tag_t
Chipset tag for the MCA bus.
.It Fa mca_intr_handle_t
The opaque handle describing an established interrupt handler.
.It Fa struct mca_attach_args
A structure use to inform the driver of MCA bus properties.
It contains the following members:
.Bd -literal
	bus_space_tag_t ma_iot;		/* MCA I/O space tag */
	bus_space_tag_t ma_memt;	/* MCA mem space tag */
	bus_dma_tag_t ma_dmat;		/* MCA DMA tag */
	int ma_slot;			/* MCA slot number */
	int ma_pos[8];			/* MCA POS values */
	int ma_id;			/* MCA device */
.Ed
.El
.Sh FUNCTIONS
.Bl -tag -width compact
.It Fn mca_intr_establish "mc" "hdl" "level" "handler" "arg"
Establish a MCA interrupt handler on the MCA bus specified by
.Fa mc
for the interrupt described completely by
.Fa hdl .
The priority of the interrupt is specified by
.Fa level .
When the interrupt occurs the function
.Fa handler
is called with argument
.Fa arg .
.It Fn mca_intr_disestablish "mc" "hdl"
Dis-establish the interrupt handler on the MCA bus specified by
.Fa mc
for the interrupt described completely
.Fa hdl .
.It Fn mca_intr_evcnt "mc" "hdl"
Do interrupt event counting on the MCA bus specified by
.Fa mc
for the event described completely by
.Fa hdl .
.It Fn mca_conf_read "mc" "slot" "reg"
Read the POS register
.Fa reg
for the device in slot
.Fa slot
on the MCA bus specified by
.Fa mc .
.It Fn mca_conf_write "mc" "slot" "reg" "data"
Write data
.Fa data
to the POS register
.Fa reg
for the device in slot
.Fa slot
on the MCA bus specified by
.Fa mc .
.El
.Sh AUTOCONFIGURATION
The MCA bus is a direct-connection bus.
During autoconfiguration, the parent specifies the MCA device ID for the
found device in the
.Fa ma_id
member of the
.Em mca_attach_args
structure.
Drivers should match on the device ID.
Device capabilities and configuration information should be read from
device POS registers using
.Fn mca_conf_read .
Some important configuration information found in the POS registers
include the I/O base address, memory base address and interrupt
number.
The location of these configurable options with the POS registers are
device specific.
.Sh DMA SUPPORT
The MCA bus supports 32-bit, bidirectional DMA transfers.
Currently, no machine-independent support for MCA DMA is available.
.Sh CODE REFERENCES
The MCA subsystem itself is implemented within the file
.Pa sys/dev/mca/mca_subr.c .
Machine-dependent portions can be found in
.Pa sys/arch/<arch>/mca/mca_machdep.c .
The database of known devices exists within the file
.Pa sys/dev/mca/mcadevs_data.h
and is generated automatically from the file
.Pa sys/dev/mca/mcadevs .
New vendor and product identifiers should be added to this file.
The database can be regenerated using the Makefile
.Pa sys/dev/mca/Makefile.mcadevs .
.Pp
A good source of information about MCA devices is IBM's system
configuration disk.
The disk contains .adf files which describe the location of device
configuration options in the POS registers.
.Sh SEE ALSO
.Xr mca 4 ,
.Xr autoconf 9 ,
.Xr bus_dma 9 ,
.Xr bus_space 9 ,
.Xr driver 9 ,
.Xr isa 9
.Sh BUGS
The machine-independent
.Nm
driver does not currently support DMA.
MCA devices which require DMA operation currently access the DMA
capabilities directly.