man pages section 9: DDI and DKI Kernel Functions

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Updated: July 2014
 
 

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)