userdma(D3X)

NAME
     userdma,undma - lock, unlock physical memory in user space

SYNOPSIS
     #include "sys/types.h"
     #include "sys/buf.h"

     userdma(void *usr_v_addr, size_t num_bytes, int rw void *MBZ);

     undma(void *usr_v_addr, size_t num_bytes, int rw);

   Arguments
     usr_v_addr
          User process address space.

     num_bytes
          Number of bytes.

     rw   If set to B_READ, then the memory space will be readable upon return
          from this call.  If set to B_WRITE, the memory will be writable upon
          return.

     MBZ must be set to 0.

DESCRIPTION
     userdma prepares memory before a DMA operation into or from a user
     process' address space.  It locks the physical pages associated with
     num_bytes bytes of user virtual memory starting at location usr_v_addr.
     If the rw flag is set to B_READ, then the memory space will be readable
     upon return from this call.  If, however, the flag is set to B_WRITE, the
     memory will be writable upon return.  userdma also invalidates the data
     cache lines corresponding to the given address and count, if necessary.

     When the operation is complete, call undma to unlock these pages.

RETURN VALUES
     If userdma is successful, it returns 0; otherwise, it returns an error
     number as follows:

     EFAULT
          The user buffer was outside the allocated address space.

     EAGAIN
          Total amount of system memory to lock user pages is temporarily
          insufficient.

     EBUSY
          There is not enough kernel memory available to map the user pages to
          kernel virtual memory.