freebsd man page for getrbuf

getrbuf(9F)						   Kernel Functions for Drivers 					       getrbuf(9F)

NAME

       getrbuf - get a raw buffer header

SYNOPSIS

       #include <sys/buf.h>
       #include <sys/kmem.h>
       #include <sys/ddi.h>

       struct buf *getrbuf(int sleepflag);

INTERFACE LEVEL

       Architecture independent level 1 (DDI/DKI).

PARAMETERS

       sleepflag       Indicates whether driver should sleep for free space.

DESCRIPTION

       getrbuf()  allocates  the  space  for a buffer header to the caller.  It is used in cases where a block driver is performing raw (character
       interface) I/O and needs to set up a buffer header that is not associated with the buffer cache.

       getrbuf() calls	kmem_alloc(9F) to perform the memory allocation.
	 kmem_alloc()requires the information included in the sleepflag argument.  If  sleepflag is set to KM_SLEEP, the driver  may  sleep  until
       the  space  is freed up.  If sleepflag is set to   KM_NOSLEEP, the driver will not sleep.  In either case, a pointer to the allocated space
       is returned or NULL to indicate that no space was available.

RETURN VALUES

       getrbuf() returns a pointer to the allocated buffer header, or  NULL if no space is available.

CONTEXT

       getrbuf() can be called from user or interrupt context. (Drivers must not allow getrbuf() to sleep if called from an interrupt routine.)

SEE ALSO

       bioinit(9F), freerbuf(9F), kmem_alloc(9F), kmem_free(9F)

       Writing Device Drivers

SunOS 5.10							    20 Nov 1996 						       getrbuf(9F)