NetBSD/share/man/man9/mca.9

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.\" $NetBSD: mca.9,v 1.7 2003/04/16 13:35:30 wiz Exp $
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.\"
.\" Copyright (c) 2001 The NetBSD Foundation, Inc.
.\" All rights reserved.
.\"
.\" 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 machine/bus.h
.In dev/mca/mcavar.h
.In dev/mca/mcadevs.h
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.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
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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.
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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
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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.
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.Pp
The MCA bus uses level-triggered interrupts while the ISA bus uses
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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.
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.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
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The MCA bus is a direct-connection bus.
During autoconfiguration, the parent specifies the MCA device ID for the
found device in the
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.Fa ma_id
member of the
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.Em mca_attach_args
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structure.
Drivers should match on the device ID.
Device capabilities and configuration information should be read from
device POS registers using
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.Fn mca_conf_read .
Some important configuration information found in the POS registers
include the I/O base address, memory base address and interrupt
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number.
The location of these configurable options with the POS registers are
device specific.
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.Sh DMA SUPPORT
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The MCA bus supports 32-bit, bidirectional DMA transfers.
Currently, no machine-independent support for MCA DMA is available.
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.Sh CODE REFERENCES
This section describes places within the
.Nx
source tree where actual code implementing or using the
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machine-independent MCA subsystem can be found.
All pathnames are relative to
.Pa /usr/src .
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.Pp
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/\*[Lt]arch\*[Gt]/mca/mca_machdep.c .
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The database of known devices exists within the file
.Fa sys/dev/mca/mcadevs_data.h
and is generated automatically from the file
.Pa sys/dev/mca/mcadevs .
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New vendor and product identifiers should be added to this file.
The database can be regenerated using the Makefile
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.Pa sys/dev/mca/Makefile.mcadevs .
.Pp
A good source of information about MCA devices is IBM's system
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configuration disk.
The disk contains .adf files which describe the location of device
configuration options in the POS registers.
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.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
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driver does not currently support DMA.
MCA devices which require DMA operation currently access the DMA
capabilities directly.