ddi_mem_alloc(9F) Kernel Functions for Drivers ddi_mem_alloc(9F)NAME
ddi_mem_alloc, ddi_mem_free - allocate and free sequentially accessed
memory
SYNOPSIS
#include <sys/ddi.h>
#include <sys/sunddi.h>
int ddi_mem_alloc(dev_info_t *dip, ddi_dma_lim_t *limits, uint_t
length, uint_t flags, caddr_t *kaddrp, uint_t *real_length);
void ddi_mem_free(caddr_t kaddr);
INTERFACE LEVEL
These interfaces are obsolete. ddi_dma_mem_alloc(9F) and
ddi_dma_mem_free(9F) should be used instead.
PARAMETERSddi_mem_alloc()
dip A pointer to the device's dev_info structure.
limits A pointer to a DMA limits structure for this device
(see ddi_dma_lim_sparc(9S) or ddi_dma_lim_x86(9S)). If
this pointer is NULL, a default set of DMA limits is
assumed.
length The length in bytes of the desired allocation.
flags The possible flags 1 and 0 are taken to mean, respec‐
tively, wait until memory is available, or do not wait.
kaddrp On a successful return, *kaddrp points to the allocated
memory.
real_length The length in bytes that was allocated. Alignment and
padding requirements may cause ddi_mem_alloc() to allo‐
cate more memory than requested in length.
ddi_mem_free()
kaddr The memory returned from a successful call to
ddi_mem_alloc().
DESCRIPTION
The ddi_mem_alloc() function allocates memory for DMA transfers and
should be used if the device is performing sequential, unidirectional,
block-sized and block-aligned transfers to or from memory. This type of
access is commonly known as streaming access. The allocation will obey
the alignment and padding constraints as specified by the limits argu‐
ment and other limits imposed by the system.
Note that you must still use DMA resource allocation functions (see
ddi_dma_setup(9F)) to establish DMA resources for the memory allocated
using ddi_mem_alloc(). ddi_mem_alloc() returns the actual size of the
allocated memory object. Because of padding and alignment require‐
ments, the actual size might be larger than the requested size.
ddi_dma_setup(9F) requires the actual length.
In order to make the view of a memory object shared between a CPU and a
DMA device consistent, explicit synchronization steps using
ddi_dma_sync(9F) or ddi_dma_free(9F) are required.
The ddi_mem_free() function frees up memory allocated by
ddi_mem_alloc().
RETURN VALUES
The ddi_mem_alloc() function returns:
DDI_SUCCESS Memory successfully allocated.
DDI_FAILURE Allocation failed.
CONTEXT
The ddi_mem_alloc() function can be called from user, interrupt, or
kernel context, except when flags is set to 1, in which case it cannot
be called from interrupt context.
ATTRIBUTES
See attributes(5) for a description of the following attributes:
┌─────────────────────────────┬─────────────────────────────┐
│ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├─────────────────────────────┼─────────────────────────────┤
│Stability Level │Obsolete │
└─────────────────────────────┴─────────────────────────────┘
SEE ALSOattributes(5), ddi_dma_free(9F), ddi_dma_mem_alloc(9F),
ddi_dma_mem_free(9F), ddi_dma_setup(9F), ddi_dma_sync(9F),
ddi_iopb_alloc(9F), ddi_dma_lim_sparc(9S), ddi_dma_lim_x86(9S),
ddi_dma_req(9S)
Writing Device Drivers
SunOS 5.10 04 Apr 2006 ddi_mem_alloc(9F)