mmap(D2)                                                    mmap(D2)


       NAME
             mmap - support virtual mapping for memory-mapped device

       SYNOPSIS
             #include <sys/types.h>
             #include <sys/mman.h>
             #include <sys/vm.h>
             #include <sys/ddi.h>
             int prefixmmap(dev_t dev, off_t off, int prot);

          Arguments
             dev   Device whose memory is to be mapped.

             off   Offset within device memory at which mapping begins.

             prot  Protection flags from mman.h.

       DESCRIPTION
             The mmap entry point provides a way to support character
             drivers for memory-mapped devices.  A memory-mapped device has
             memory that can be mapped into a process's address space.  The
             mmap(2) system call, when applied to a character special file,
             allows this device memory to be mapped into user space for
             direct access by the user application (this way no kernel
             buffering or system call overhead is incurred).

             The mmap routine checks if the offset is within the range of
             pages supported by the device.  For example, a device that has
             32K bytes of memory that can be mapped into user space should
             not support offsets greater than, or equal to, 32K.  If the
             offset does not exist, then NOPAGE is returned.  If the offset
             does exist, the mmap routine returns the physical page ID for
             the page at offset off in the device's memory.

          Return Values
             If the protection and offset are valid for the device, the
             driver should return the physical page ID.  Otherwise, NOPAGE
             should be returned.

       USAGE
             This entry point is optional, and valid for memory-mapped
             character device or character pseudo-device drivers only.

             Valid values for prot are:




                           Copyright 1994 Novell, Inc.               Page 1

      mmap(D2)                                                    mmap(D2)


                  PROT_READ     Page can be read.

                  PROT_WRITE    Page can be written.

                  PROT_EXEC     Page can be executed.

                  PROT_USER     Page is accessible from user-level.

                  PROT_ALL      All of the above.

            A physical page ID is a machine-specific token that uniquely
            identifies a page of physical memory in the system (either
            kernel memory or device memory).  To get the physical page ID
            for a given virtual address, drivers should use the
            hat_getkpfnum(D3) function (on SVR4.0, SVR4.1ES and SVR4.2
            systems) or the kvtoppid(D3) function (on SVR4MP and SVR4.2 MP
            systems).  To get the physical page ID for a given physical
            address, drivers should use the hat_getppfnum(D3) function (on
            SVR4.0, SVR4.1ES and SVR4.2 systems) or the phystoppid(D3)
            function (on SVR4MP and SVR4.2 MP systems).

            No assumptions should be made about the format of a physical
            page ID.

         Synchronization Constraints
            The mmap routine has user context and can sleep.

      REFERENCES
            hat_getkpfnum(D3), hat_getppfnum(D3), kvtoppid(D3), mmap(2),
            phystoppid(D3)

      NOTICES
         Portability
            All processors

         Applicability
            ddi: 1, 2, 3, 4, 5, 5mp, 6, 6mp, 7, 7mp











                          Copyright 1994 Novell, Inc.               Page 2