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

     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

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

     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);

     isa_intr_disestablish(isa_chipset_tag_t ic, void *ih);

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

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

     isa_dmamap_destroy(isa_chipset_tag_t ic, int chan);

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

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

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

     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);

     isa_free(void *addrp, int pool);

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

     isa_dmaabort(isa_chipset_tag_t ic, int chan);

     isa_dmacount(isa_chipset_tag_t ic, int chan);

     isa_dmadone(isa_chipset_tag_t ic, int chan);

     isa_dmamaxsize(isa_chipset_tag_t ic, int chan);

     isa_drq_alloc(isa_chipset_tag_t ic, int chan);

     isa_drq_free(isa_chipset_tag_t ic, int chan);

     isa_drq_isfree(isa_chipset_tag_t ic, int chan);

     isa_dmacascade(isa_chipset_tag_t ic, int chan);

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

     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
     acceptance 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,
     preventing 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.

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

              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 */

     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:

                       Reserve interrupt, but don't actually establish.

                       Edge-triggered interrupt.

                       Level-triggered interrupt.

                       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_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
              success 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
              specified by addr and size respectively.

     isa_dmamem_map(ic, chan, addr, size, kvap, flags)
              Maps DMA-safe memory (allocated with isa_dmamem_alloc())
              specified 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

     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
              argument pool is a pool to record the memory allocation.  This
              function 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
              argument lwp is used to indicate the address space in which the
              buffer is located.  If NULL, the buffer is assumed to be in
              kernel 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:

                       DMA transfer from host to device.

                       DMA transfer to host from device.

                       Transfer buffer once and stop.

                       Demand mode.

                       Transfer buffer continuously in loop until notified to

                       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

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

     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

     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.

     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
     "locations" 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
     locators 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)).

     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
     memory 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

     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().

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

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

     The machine-independent ISA subsystem appeared in NetBSD 1.2.

     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 10.99                   January 29, 2006                   NetBSD 10.99