contig_malloc(9r)														 contig_malloc(9r)

NAME

       contig_malloc - General: Allocates physically contiguous memory

SYNOPSIS

       #include <sys/malloc.h>

       void * contig_malloc(
	       u_long size,
	       u_long alignment,
	       u_long addrlimit,
	       int type,
	       int flag );

ARGUMENTS

       Specifies  the  size  of  the  memory  (in  bytes)  to allocate.  Specifies the alignment of the memory to be allocated. For example, for a
       256-byte alignment, you should pass the value 256. A 0 (zero) value means there is no alignment requirement.  Specifies that the address of
       all  the  allocated memory should be less than or equal to this address. A 0 (zero) value means that there is no address limit requirement.
       Specifies the purpose for which	the  memory  is  being	allocated  (or	freed).  The  memory  type  constants  are  defined  in  the  file
       /usr/sys/include/sys/malloc.h.  Examples  of  memory  type  constants  are M_DEVBUF (device driver memory), M_KTABLE (kernel table memory),
       M_RTABLE (routing tables memory), and so forth.	Specifies one of the following flags defined in  /usr/sys/include/sys/malloc.h:  Signifies
       that contig_malloc should zero the allocated memory.  Signifies that contig_malloc can block.  Signifies that contig_malloc cannot block.

DESCRIPTION

       The  contig_malloc routine allocates physically contiguous memory during the boot process (before single-user mode). The routine carves out
       an area of physically contiguous memory from a contiguous memory buffer and allocates memory from this buffer with  proper  alignment.  The
       call to contig_malloc is the same for statically or dynamically configured drivers. However, the point or points in time in which the stat-
       ically or dynamically configured driver requests the memory differ.

       A statically configured driver typically needs to call contig_malloc only before single-user mode. In this case, contig_malloc obtains  the
       memory  from the contiguous memory buffer. When a statically configured driver frees this physically contiguous memory (by calling the con-
       tig_free routine), the memory is returned to the virtual memory subsystem.

       A dynamically configured driver typically needs physically contiguous memory after single-user mode. As	stated	previously,  contig_malloc
       carves  out an area of physically contiguous memory from a contiguous memory buffer before single-user mode. Thus, this memory would not be
       available to the dynamically configured driver after single-user mode. To solve this problem, a dynamically configured  driver  calls  con-
       tig_malloc by defining the CMA_Option attribute in the sysconfigtab file fragment.

       The  cma_dd  subsystem  calls  contig_malloc on behalf of dynamically configured device drivers and obtains the memory allocation size (and
       other information) from the CMA_Option attribute field. In this case, contig_malloc allocates physically contiguous memory  from  the  con-
       tiguous	memory buffer and places it in a saved memory pool. When a dynamically configured driver needs to call contig_malloc after single-
       user mode, the physically contiguous memory comes from this saved memory pool. When a dynamically configured driver frees  this	physically
       contiguous  memory (by calling the contig_free routine), the memory is returned to the saved memory pool (not to the virtual memory subsys-
       tem). Thus, this physically contiguous memory is available to the dynamically configured driver upon subsequent reload requests that  occur
       after single-user mode.

RETURN VALUES

       Upon successful completion, contig_malloc returns a pointer to the allocated memory. If contig_malloc cannot allocate the requested memory,
       it returns a null pointer.

SEE ALSO

       Routines: contig_free(9r)

																 contig_malloc(9r)