udbufalloc(3X)                                     udbufalloc(3X)



NAME
     udbufalloc, udbuffree - allocate a user-level buffer descip-
     tor

SYNOPSIS
     udbuft *udbufalloc (buffer, size, userdmaflags)
     char *buffer;
     int size;
     int userdmaflags;

     void udbuffree (udbuf)
     udbuft *udbuf;

DESCRIPTION
     udbufalloc and udbuffree provide a simple general-purpose
     buffer descriptor to provide consistent information across
     user-level device handlers.  udbufalloc returns a pointer to
     a udbuf_t type structure which provides a description of the
     physical memory fragmentation of a buffer in user space.
     udbufalloc expects a pointer to a buffer within a user's
     program and the buffer's size to be provided as arguments.
     The size of the buffer should be provided in terms of bytes.
     Additionally, udbufalloc expects some userdma(2) flags to be
     provided as the third argument.  These flags determine the
     appropriate caching properties for the buffer.  See
     userdma(2) for further information on valid flags.

     The argument to udbuffree is a pointer to a udbuf_t type
     previously allocated by udbufalloc; the memory allocated for
     the udbuft structure will be freed and the cache and memory
     locks on the user buffer will be returned to their state
     before the call to udbufalloc.

     These routines require that the calling process have
     plock(2) permission.  The udbufalloc(3X) routine calls the
     userdma(2) system service which imposes several requirements
     and restrictions for the use of this routine.  The user
     should check the userdma(2) man page for further informa-
     tion.

     It is very importantant that the argument passed to the
     udbuffree(3X) routine be a pointer returned from a
     udbufalloc(3X) routine.

RETURN VALUE
     Udbuffalloc returns a null pointer (0) if there is no avail-
     able memory to allocate for the buffer descriptor or if the
     attempt to lock down the user buffer fails.  Errno is set to
     indicate the error.

ERRORS
     [ENOMEM]       There was not enough memory to allocate a



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udbufalloc(3X)                                     udbufalloc(3X)



                    buffer descriptor.

                    For more error codes see userdma(2).

SEE ALSO
     userdma(2).

















































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