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


Solaris DDI specific (Solaris 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.

SEE ALSO


ddi_umem_lock(9F), ddi_dma_buf_bind_handle(9F), freerbuf(9F), physio(9F),
buf(9S)


February 4, 2003 DDI_UMEM_IOSETUP(9F)