MCA(9)							   BSD Kernel Developer's Manual						    MCA(9)

NAME

     MCA, mca_intr_establish, mca_intr_disestablish, mca_intr_evcnt, mca_conf_read, mca_conf_write -- MicroChannel Architecture bus

SYNOPSIS

     #include <sys/bus.h>
     #include <dev/mca/mcavar.h>
     #include <dev/mca/mcadevs.h>

     void *
     mca_intr_establish(mca_chipset_tag_t mc, mca_intr_handle_t hdl, int level, int (*handler)(void *), void *arg);

     void
     mca_intr_disestablish(mca_chipset_tag_t mc, mca_intr_handle_t hdl);

     const struct evcnt *
     mca_intr_evcnt(mca_chipset_tag_t mc, mca_intr_handle_t hdl);

     int
     mca_conf_read(mca_chipset_tag_t mc, int slot, int reg);

     void
     mca_conf_write(mca_chipset_tag_t mc, int slot, int reg, int data);

DESCRIPTION

     The MCA 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.

     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 regis-
     ters is performed using IBM's system configuration software.

     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.

DATA TYPES

     Drivers for devices attached to the MCA bus will make use of the following data types:

     mca_chipset_tag_t
	      Chipset tag for the MCA bus.

     mca_intr_handle_t
	      The opaque handle describing an established interrupt handler.

     struct mca_attach_args
	      A structure use to inform the driver of MCA bus properties.  It contains the following members:

		      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 */

FUNCTIONS

     mca_intr_establish(mc, hdl, level, handler, arg)
	      Establish a MCA interrupt handler on the MCA bus specified by mc for the interrupt described completely by hdl.  The priority of the
	      interrupt is specified by level.	When the interrupt occurs the function handler is called with argument arg.

     mca_intr_disestablish(mc, hdl)
	      Dis-establish the interrupt handler on the MCA bus specified by mc for the interrupt described completely hdl.

     mca_intr_evcnt(mc, hdl)
	      Do interrupt event counting on the MCA bus specified by mc for the event described completely by hdl.

     mca_conf_read(mc, slot, reg)
	      Read the POS register reg for the device in slot slot on the MCA bus specified by mc.

     mca_conf_write(mc, slot, reg, data)
	      Write data data to the POS register reg for the device in slot slot on the MCA bus specified by mc.

AUTOCONFIGURATION

     The MCA bus is a direct-connection bus.  During autoconfiguration, the parent specifies the MCA device ID for the found device in the ma_id
     member of the mca_attach_args structure.  Drivers should match on the device ID.  Device capabilities and configuration information should be
     read from device POS registers using 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 spe-
     cific.

DMA SUPPORT

     The MCA bus supports 32-bit, bidirectional DMA transfers.	Currently, no machine-independent support for MCA DMA is available.

CODE REFERENCES

     The MCA subsystem itself is implemented within the file sys/dev/mca/mca_subr.c.  Machine-dependent portions can be found in
     sys/arch/<arch>/mca/mca_machdep.c.  The database of known devices exists within the file sys/dev/mca/mcadevs_data.h and is generated automat-
     ically from the file sys/dev/mca/mcadevs.	New vendor and product identifiers should be added to this file.  The database can be regenerated
     using the Makefile sys/dev/mca/Makefile.mcadevs.

     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.

SEE ALSO

     mca(4), autoconf(9), bus_dma(9), bus_space(9), driver(9), isa(9)

BUGS

     The machine-independent MCA driver does not currently support DMA.  MCA devices which require DMA operation currently access the DMA capabil-
     ities directly.

BSD
								  October 7, 2001							       BSD