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Kernel Functions for Drivers

ddi_mem_alloc(9F)

INTERFACE LEVEL
PARAMETERS
DESCRIPTION
RETURN VALUES
CONTEXT
SEE ALSO

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);

PARAMETERS

ddi_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_IA(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, respectively, 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 allocate more memory than requested in length.

ddi_mem_free

kaddr: The memory returned from a successful call to ddi_mem_alloc().

ddi_mem_alloc() 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 argument 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 requirements, 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.

ddi_mem_free() frees up memory allocated by ddi_mem_alloc().

RETURN VALUES

ddi_mem_alloc() returns:

DDI_SUCCESS: Memory successfully allocated.
DDI_FAILURE: Allocation failed.

CONTEXT

ddi_mem_alloc() can be called from user or interrupt context, except when flags is set to 1, in which case it can be called from user context only.