ISA(9)                 NetBSD Kernel Developer's Manual                 ISA(9)

NAME
     ISA, isa_intr_alloc, isa_intr_establish, isa_intr_disestablish,
     isa_intr_evcnt, isa_dmamap_create, isa_dmamap_destroy, isa_dmamem_alloc,
     isa_dmamem_free, isa_dmamem_map, isa_dmamem_unmap, isa_malloc, isa_free,
     isa_dmastart, isa_dmaabort, isa_dmacount, isa_dmadone, isa_dmamaxsize,
     isa_drq_alloc, isa_drq_free, isa_drq_isfree, isa_dmacascade, isa_mappage
     -- Industry-standard Architecture

SYNOPSIS
     #include <machine/bus.h>
     #include <dev/isa/isareg.h>
     #include <dev/isa/isavar.h>

     int
     isa_intr_alloc(isa_chipset_tag_t ic, int mask, int type, int *irq);

     const struct evcnt *
     isa_intr_evcnt(isa_chipset_tag_t ic, int irq);

     void *
     isa_intr_establish(isa_chipset_tag_t ic, int irq, int type, int level,
         int (*handler)(void *), void *arg);

     void
     isa_intr_disestablish(isa_chipset_tag_t ic, void *ih);

     #include <dev/isa/isadmareg.h>
     #include <dev/isa/isadmavar.h>

     int
     isa_dmamap_create(isa_chipset_tag_t ic, int chan, bus_size_t size,
         int flags);

     void
     isa_dmamap_destroy(isa_chipset_tag_t ic, int chan);

     int
     isa_dmamem_alloc(isa_chipset_tag_t ic, int chan, bus_size_t size,
         bus_addr_t *addrp, int flags);

     void
     isa_dmamem_free(isa_chipset_tag_t ic, int chan, bus_addr_t addr,
         bus_size_t size);

     int
     isa_dmamem_map(isa_chipset_tag_t ic, int chan, bus_addr_t addr,
         bus_size_t size, void **kvap, int flags);

     void
     isa_dmamem_unmap(isa_chipset_tag_t ic, int chan, void *kva, size_t size);

     void *
     isa_malloc(isa_chipset_tag_t ic, int chan, size_t size, int pool,
         int flags);

     void
     isa_free(void *addrp, int pool);

     int
     isa_dmastart(isa_chipset_tag_t ic, int chan, bus_addr_t addr,
         bus_size_t size, struct lwp *lwp, int flags, int bf);

     void
     isa_dmaabort(isa_chipset_tag_t ic, int chan);

     bus_size_t
     isa_dmacount(isa_chipset_tag_t ic, int chan);

     void
     isa_dmadone(isa_chipset_tag_t ic, int chan);

     bus_size_t
     isa_dmamaxsize(isa_chipset_tag_t ic, int chan);

     int
     isa_drq_alloc(isa_chipset_tag_t ic, int chan);

     int
     isa_drq_free(isa_chipset_tag_t ic, int chan);

     int
     isa_drq_isfree(isa_chipset_tag_t ic, int chan);

     int
     isa_dmacascade(isa_chipset_tag_t ic, int chan);

     paddr_t
     isa_mappage(void *mem, off_t offset, int prot);

DESCRIPTION
     The machine-independent ISA subsystem provides support for the ISA bus.

     The ISA bus was introduced on the IBM PC/AT.  It is an extension to the
     original bus found on the original IBM PC.  The ISA bus is essentially
     the host bus of the Intel 80286 processor, however the widespread accep-
     tance of the bus as a de facto standard has seen it appear on systems
     without Intel processors.

     The ISA bus has a 16-bit data bus, a 24-bit memory address bus, a 16-bit
     I/O address bus, and operates at 8MHz.  It provides 15 interrupt lines
     and 8 DMA channels supporting DMA transfers of 64KB or 128KB transfers
     depending on the width of the channel being used.  Historically, some
     devices only decoded the 10 lowest bits of the I/O address bus, prevent-
     ing use of the full 16-bit address space.

     On newer machines, the ISA bus is no longer connected directly to the
     host bus, and is usually connected via a PCI-ISA bridge.  Either way, the
     bus looks the same to the device driver.

DATA TYPES
     Drivers for devices attached to the ISA bus will make use of the follow-
     ing data types:

     isa_chipset_tag_t
              Chipset tag for the ISA bus.

     struct isa_attach_args
              Location hints for devices are recorded in this structure.  It
              contains the following members:

                      bus_space_tag_t ia_iot;         /* isa i/o space tag */
                      bus_space_tag_t ia_memt;        /* isa mem space tag */
                      bus_dma_tag_t ia_dmat;          /* DMA tag */
                      isa_chipset_tag_t ia_ic;
                      int ia_iobase;                  /* base i/o address */
                      int ia_iosize;                  /* span of ports used */
                      int ia_maddr;                   /* physical mem addr */
                      u_int ia_msize;                 /* size of memory */
                      int ia_irq;                     /* interrupt request */
                      int ia_drq;                     /* DMA request */
                      int ia_drq2;                    /* second DMA request */
                      void *ia_aux;                   /* driver specific */

FUNCTIONS
     isa_intr_alloc(ic, mask, type, irq)
              This function is generally not required by device drivers.  It
              is used by bridges attaching other busses to the ISA bus.

     isa_intr_evcnt(ic, irq)
              Returns the event counter associated with interrupt line irq.

     isa_intr_establish(ic, irq, type, level, handler, arg)
              To establish an ISA interrupt handler, a driver calls
              isa_intr_establish() with the interrupt number irq, type type,
              and level level.  When the interrupt occurs the function handler
              is called with argument arg.  Valid values for type are:

              IST_NONE
                       Reserve interrupt, but don't actually establish.

              IST_EDGE
                       Edge-triggered interrupt.

              IST_LEVEL
                       Level-triggered interrupt.

              IST_PULSE
                       Pulse-triggered interrupt.

              isa_intr_establish() returns an opaque handle to an event
              descriptor if it succeeds, and returns NULL on failure.

     isa_intr_disestablish(ic, ih)
              Dis-establish the interrupt handler with handle ih.  The handle
              was returned from isa_intr_establish().

     isa_drq_alloc(ic, chan)
              Reserves the DMA channel chan for future use.  Normally, this
              call precedes an isa_dmamap_create() call.  It is an error to
              start DMA on a channel that has not been reserved with
              isa_drq_alloc().

     isa_drq_free(ic, chan)
              Marks the DMA channel chan as available again.

     isa_dmamap_create(ic, chan, size, flags)
              Creates a DMA map for channel chan.  It is initialised to accept
              maximum DMA transfers of size size.  Valid values for the flags
              argument are the same as for bus_dmamap_create() (see
              bus_dma(9)).  This function returns zero on success or an error
              value on failure.

     isa_dmamap_destroy(ic, chan)
              Destroy the DMA map for DMA channel chan.

     isa_dmamem_alloc(ic, chan, size, addrp, flags)
              Allocate DMA-safe memory of size size for channel chan.  Valid
              values for the flags argument are the same as for
              bus_dmamem_alloc() (see bus_dma(9)).  The bus-address of the
              memory is returned in addrp.  This function returns zero on suc-
              cess or an error value on failure.

     isa_dmamem_free(ic, chan, addr, size)
              Frees memory previously allocated by isa_dmamem_alloc() for
              channel chan.  The bus-address and size of the memory are speci-
              fied by addr and size respectively.

     isa_dmamem_map(ic, chan, addr, size, kvap, flags)
              Maps DMA-safe memory (allocated with isa_dmamem_alloc()) speci-
              fied by bus-address addr and of size size into kernel virtual
              address space for DMA channel chan.  Valid values for the flags
              argument are the same as for bus_dmamem_map() (see bus_dma(9)).
              The kernel virtual address is returned in kvap.  This function
              returns zero on success or an error value on failure.

     isa_dmamem_unmap(ic, chan, kva, size)
              Unmaps memory (previously mapped with isa_dmamem_map()) of size
              size for channel chan.  The kernel virtual address space used by
              the mapping is freed.

     isa_malloc(ic, chan, size, pool, flags)
              This function is a shortcut for allocating and mapping DMA-safe
              memory in a single step.  The arguments correspond with the
              arguments to isa_dmamem_alloc() and isa_dmamem_map().  The argu-
              ment pool is a pool to record the memory allocation.  This func-
              tion returns a pointer to the DMA-safe memory.

     isa_free(addrp, pool)
              This function is a shortcut for unmapping and deallocating DMA-
              safe memory in a single step.  It replaces isa_dmamem_unmap()
              and isa_dmamem_free().  The argument addrp is the pointer to the
              DMA-safe memory returned by isa_malloc().  The argument pool is
              the same as the value passed to isa_malloc().

     isa_dmastart(ic, chan, addr, size, lwp, flags, bf)
              Load DMA memory specified by address addr of size size into the
              DMA controller at channel chan and set it in motion.  The argu-
              ment lwp is used to indicate the address space in which the
              buffer is located.  If NULL, the buffer is assumed to be in ker-
              nel space.  Otherwise, the buffer is assumed to be in lwp lwp 's
              address space.  The argument flags describes the type of ISA
              DMA.  Valid values are:

              DMAMODE_WRITE
                       DMA transfer from host to device.

              DMAMODE_READ
                       DMA transfer to host from device.

              DMAMODE_SINGLE
                       Transfer buffer once and stop.

              DMAMODE_DEMAND
                       Demand mode.

              DMAMODE_LOOP
                       Transfer buffer continuously in loop until notified to
                       stop.

              DMAMODE_LOOPDEMAND
                       Transfer buffer continuously in loop and demand mode.

              The argument bf is the bus-space flags.  Valid values are the
              same as for bus_dmamap_load() (see bus_dma(9)).

     isa_dmaabort(ic, chan)
              Abort a DMA transfer on channel chan.

     isa_dmacount(ic, chan)
              Returns the offset in the DMA memory of the current DMA transfer
              on channel chan.

     isa_dmadone(ic, chan)
              Unloads the DMA memory on channel chan after a DMA transfer has
              completed.

     isa_dmamaxsize(ic, chan)
              Returns the maximum allowable DMA transfer size for channel
              chan.

     isa_drq_isfree(ic, chan)
              If the ia_drq or ia_drq2 members of struct isa_attach_args are
              wildcarded, then the driver is expected to probe the hardware
              for valid DMA channels.  In this case, the driver can check to
              see if the hardware-supported DMA channel chan is available for
              use.

     isa_dmacascade(ic, chan)
              Programs the 8237 DMA controller channel chan to accept external
              DMA control by the device hardware.

     isa_mappage(mem, offset, prot)
              Provides support for user mmap(2)'ing of DMA-safe memory.

AUTOCONFIGURATION
     The ISA bus is an indirect-connection bus.  During autoconfiguration each
     driver is required to probe the bus for the presence of a device.  An ISA
     driver will receive a pointer to struct isa_attach_args hinting at "loca-
     tions" on the ISA bus where the device may be located.  They should use
     the ia_iobase, ia_iosize, ia_maddr, and ia_msize members.  Not all of
     these hints will be necessary; locators may be wildcarded with IOBASEUNK
     and MADDRUNK for ia_iobase and ia_maddr respectively.  If a driver can
     probe the device for configuration information at default locations, it
     may update the members of struct isa_attach_args.  The IRQ and DMA loca-
     tors can also be wildcarded with IRQUNK and DRQUNK respectively.

     During the driver attach step, the I/O and memory address spaces should
     be mapped (see bus_space(9)).

DMA SUPPORT
     Extensive DMA facilities are provided for the ISA bus.  A driver can use
     up to two DMA channels simultaneously.  The DMA channels allocated during
     autoconfiguration are passed to the driver during the driver attach using
     the ia_drq and ia_drq2 members of struct isa_attach_args.

     Before allocating resources for DMA transfers on the ISA bus, a driver
     should check the maximum allowable DMA transfer size for the DMA channel
     using isa_dmamaxsize().

     A DMA map should be created first using isa_dmamap_create().  A DMA map
     describes how DMA memory is loaded into the DMA controllers.  Only DMA-
     safe memory can be used for DMA transfers.  DMA-safe memory is allocated
     using isa_dmamem_alloc().  The memory allocated by isa_dmamem_alloc()
     must now be mapped into kernel virtual address space by isa_dmamem_map()
     so that it can be accessed by the driver.

     For a DMA transfer from the host to the device, the driver will fill the
     DMA memory with the data to be transferred.  The DMA-transfer of the mem-
     ory is started using isa_dmastart() with flags containing DMAMODE_WRITE.
     When the DMA transfer is completed, a call to isa_dmadone() cleans up the
     DMA transfer by unloading the memory from the controller.

     For a DMA transfer from the device to the host, the DMA-transfer is
     started using isa_dmastart() with flags containing DMAMODE_READ.  When
     the DMA transfer is completed, a call to isa_dmadone() cleans up the DMA
     transfer by unloading the memory from the controller.  The memory can now
     be access by the driver.

     When the DMA resources are no longer required they should be released
     using isa_dmamem_unmap(), isa_dmamem_free() and isa_dmamap_destroy().

CODE REFERENCES
     This section describes places within the NetBSD source tree where actual
     code implementing or using the machine-independent ISA subsystem can be
     found.  All pathnames are relative to /usr/src.

     The ISA subsystem itself is implemented within the files
     sys/dev/isa/isa.c and sys/dev/isa/isadma.c.

SEE ALSO
     isa(4), autoconf(9), bus_dma(9), bus_space(9), driver(9), isapnp(9)

HISTORY
     The machine-independent ISA subsystem appeared in NetBSD 1.2.

BUGS
     The previous behaviour of isa_intr_establish() was to invoke panic() on
     failure.  isa_intr_establish() now returns NULL on failure.  Some old
     drivers written for the former behaviour discard the return value.

NetBSD 5.0_STABLE              January 29, 2006              NetBSD 5.0_STABLE
