HDK Technical Reference

Buffered I/O buffers, allocating

The operating system includes a cache of buffers that are used for block I/O transfers. The header structure for these buffers is described on the buf(D4) manual page.

See ``Memory allocation'' for information about allocating memory other than buffer cache buffers in a driver.

DDI functions

The following DDI structures are used for buffered I/O operations:

buf(D4): Buffer header structure.
bcb(D4): Breakup control block.

The following DDI functions are used to allocate buffer headers:

bcb_alloc(D3): Allocate a breakup control block
bcb_prep(D3): Prepare an allocated breakup control block
bcb_free(D3): Free a breakup control block
biodone(D3): Release buffer and unblock processes after a block I/O operation is complete.
bioerror(D3): Manipulate error fields within a buf(D4) structure.
biowait(D3): Suspend execution pending completion of a block I/O operation.
biowait_sig(D3): Suspend execution pending completion of a block I/O operation or a signal.
brelse(D3): Release buffer
buf_breakup(D3): buffer breakup routine
clrbuf(D3): Clear buffer contents
freerbuf(D3): Release buffer from getrbuf
geteblk(D3): Allocate 1024 byte buffer, return pointer
geterror(D3): Return buffer error number
getrbuf(D3): Allocate buffer header only
ngeteblk(D3): Allocate n-byte buffer, return pointer

ODDI functions

The following ODDI functions are used to allocate buffer headers:

brelse(D3oddi): Release buffer.
disksort(D3oddi): Add a block I/O request to a device's queue.
geteblk(D3oddi): Get a free buffer from the block buffer pool.
iodone(D3oddi): Release buffer and unblock processes after a block I/O operation is complete.
iowait(D3oddi): Suspend execution pending completion of a block I/O operation.
pio_breakup(D3oddi): Break up a programmed I/O request.