disksort(9F) Kernel Functions for Drivers disksort(9F)NAMEdisksort - single direction elevator seek sort for buffers
SYNOPSIS
#include <sys/conf.h>
#include <sys/ddi.h>
#include <sys/sunddi.h>
void
disksort(struct diskhd *dp, struct buf *bp);
INTERFACE LEVEL
Solaris DDI specific (Solaris DDI).
PARAMETERS
dp A pointer to a diskhd structure. A diskhd structure is essen‐
tially identical to head of a buffer structure (see buf(9S)).
The only defined items of interest for this structure are the
av_forw and av_back structure elements which are used to main‐
tain the front and tail pointers of the forward linked I/O
request queue.
bp A pointer to a buffer structure. Typically this is the I/O
request that the driver receives in its strategy routine (see
strategy(9E)). The driver is responsible for initializing the
b_resid structure element to a meaningful sort key value prior
to calling disksort().
DESCRIPTION
The function disksort() sorts a pointer to a buffer into a single for‐
ward linked list headed by the av_forw element of the argument *dp.
It uses a one-way elevator algorithm that sorts buffers into the queue
in ascending order based upon a key value held in the argument buffer
structure element b_resid.
This value can either be the driver calculated cylinder number for the
I/O request described by the buffer argument, or simply the absolute
logical block for the I/O request, depending on how fine grained the
sort is desired to be or how applicable either quantity is to the
device in question.
The head of the linked list is found by use of the av_forw structure
element of the argument *dp. The tail of the linked list is found by
use of the av_back structure element of the argument *dp. The av_forw
element of the *bp argument is used by disksort() to maintain the for‐
ward linkage. The value at the head of the list presumably indicates
the currently active disk area.
CONTEXT
This function can be called from user, interrupt, or kernel context.
SEE ALSOstrategy(9E), buf(9S)
Writing Device Drivers
WARNINGS
The disksort() function does no locking. Therefore, any locking is com‐
pletely the responsibility of the caller.
SunOS 5.10 16 Jan 2006 disksort(9F)
