SVR5

bcb_alloc(D3)

bcb_alloc -- allocate a breakup control block

Synopsis

   #include <sys/buf.h>
   #include <sys/kmem.h>
   #include <sys/ddi.h>
   
   bcb_t *bcb_alloc(int flag);

Description

bcb_alloc allocates a bcb(D4) structure, which is used to pass breakup property requirements to buf_breakup(D3).

Arguments

flag: Indicates whether the allocation may sleep or not, and is set to KM_SLEEP or KM_NOSLEEP.

Return values

On success, bcb_alloc returns a pointer to a bcb structure. If KM_NOSLEEP is specified and sufficient memory is not immediately available, bcb_alloc returns a NULL pointer.

Usage

bcb_alloc is typically called at driver startup time to allocate a bcb structure for a driver or a drive. This bcb is then used repeatedly, for each transfer, as an argument to the buf_breakup( ) function.

The bcb structure is allocated with all members set to 0.

Drivers written for DDI 8 and later versions must call the bcb_prep(D3) function before calling bcb_alloc( ).

Context and synchronization

If flag is set to KM_NOSLEEP, non-blockable, initialization, or interrupt context.

If flag is set to KM_SLEEP, user context.

Hardware applicability

All

Version applicability

ddi: 5, 5mp, 6, 6mp, 7, 7mp, 7.1, 7.1mp, 8, 8mp

Differences between versions

Drivers written for DDI versions prior to version 8 do not call the bcb_prep(D3) function before calling bcb_alloc( ).

References

bcb(D4) bcb_free(D3), bcb_alloc(D3), buf_breakup(D3)