Tribblix: manual page: ddi_umem

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

NAME

ddi_umem_iosetup - Setup I/O requests to application memory

SYNOPSIS

#include <sys/ddi.h>
#include <sys/sunddi.h>

struct buf *ddi_umem_iosetup(ddi_umem_cookie_t cookie,off_t off,
size_t len, int direction, dev_t dev, daddr_t blkno,
int (*iodone) (struct buf *), int sleepflag);

INTERFACE LEVEL

illumos DDI specific (illumos DDI)

PARAMETERS

cookie
The kernel memory cookie allocated by
ddi_umem_lock(9F).

off
Offset from the start of the cookie.

len
Length of the I/O request in bytes.

direction
Must be set to B_READ for reads from the device or
B_WRITE for writes to the device.

dev
Device number

blkno
Block number on device.

iodone
Specific biodone(9F) routine.

sleepflag
Determines whether caller can sleep for memory.
Possible flags are DDI_UMEM_SLEEP to allow sleeping
until memory is available, or DDI_UMEM_NOSLEEP to
return NULL immediately if memory is not available.

DESCRIPTION

The ddi_umem_iosetup(9F) function is used by drivers to setup I/O
requests to application memory which has been locked down using
ddi_umem_lock(9F).

The ddi_umem_iosetup(9F) function returns a pointer to a buf(9S)
structure corresponding to the memory cookie cookie. Drivers can
setup multiple buffer structures simultaneously active using the same
memory cookie. The buf(9S) structures can span all or part of the
region represented by the cookie and can overlap each other. The
buf(9S) structure can be passed to ddi_dma_buf_bind_handle(9F) to
initiate DMA transfers to or from the locked down memory.

The off parameter specifies the offset from the start of the cookie.
The len parameter represents the length of region to be mapped by the
buffer. The direction parameter must be set to either B_READ or
B_WRITE, to indicate the action that will be performed by the device.
(Note that this direction is in the opposite sense of the VM system's
direction of DDI_UMEMLOCK_READ and DDI_UMEMLOCK_WRITE.) The direction
must be compatible with the flags used to create the memory cookie in
ddi_umem_lock(9F). For example, if ddi_umem_lock() is called with the
flags parameter set to DDI_UMEMLOCK_READ, the direction parameter in
ddi_umem_iosetup() should be set to B_WRITE.

The dev parameter specifies the device to which the buffer is to
perform I/O.The blkno parameter represents the block number on the
device. It will be assigned to the b_blkno field of the returned
buffer structure. The iodone parameter enables the driver to
identify a specific biodone(9F) routine to be called by the driver
when the I/O is complete. The sleepflag parameter determines if the
caller can sleep for memory. DDI_UMEM_SLEEP allocations may sleep
but are guaranteed to succeed. DDI_UMEM_NOSLEEP allocations do not
sleep but may fail (return NULL) if memory is currently not
available.

After the I/O has completed and the buffer structure is no longer
needed, the driver calls freerbuf(9F) to free the buffer structure.

RETURN VALUES

The ddi_umem_iosetup(9F) function returns a pointer to the
initialized buffer header, or NULL if no space is available.

CONTEXT

The ddi_umem_iosetup(9F) function can be called from any context only
if flag is set to DDI_UMEM_NOSLEEP. If DDI_UMEM_SLEEP is set,
ddi_umem_iosetup(9F) can be called from user and kernel context only.