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     DB_READ(K)                UNIX System V                DB_READ(K)



     Name
          db_read - transfers data from physical memory to a user
          address

     Syntax
          int
          db_read(dv, va, count)
          struct devbuf *dv;
          caddr_t va;
          unsigned count;

     Description
          The db_read routine transfers data from physical contiguous
          memory pointed to by dv to a virtual user address va.  The
          amount transferred is in count bytes.  The physical memory
          must have been allocated by db_alloc(K).

     Warning
          Only use this routine after the requested pages are locked
          into memory by a previous call to physio(K).  Use of db_read
          under any other circumstances results in a panic.

     Example
          For example, to transfer data from dv to a user buffer:

          struct buf *bp;
          struct devbuf dv;

          db_read( &dv, paddr( bp ), bp->b_count );

     See Also
          db_alloc(K), db_write(K), physio(K)

                                                      (printed 7/6/89)