DMA pool allocator
[Memory Allocation]

Collaboration diagram for DMA pool allocator:

Data Structures
struct	dma_pool
	DMA memory pool. More...
Modules
	Generic DMA pool allocator
Functions
void	dma_pool_init_coherent_physmem (struct dma_pool *dmapool, struct physmem_pool *phys_pool, unsigned int nr_objects, size_t objsize, unsigned int align_order)
	Initialize a DMA pool using the physmem allocator.
static void	dma_pool_init_coherent (struct dma_pool *pool, phys_addr_t phys_start, size_t size, size_t objsize, unsigned int align_order)
	Initialize a DMA-coherent memory pool.
static dma_addr_t	dma_pool_alloc (struct dma_pool *pool)
	Allocate an object from a DMA pool.
static void	dma_pool_free (struct dma_pool *pool, dma_addr_t addr)
	Free an object previously allocated from pool.

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Detailed Description

This is a memory pool allocator for DMA memory. DMA memory differs from "regular" memory in that both the physical and virtual addresses are kept track of, and cache coherency issues are easier to deal with.

On cache- and MMU-less processors, DMA memory pools are essentially identical to regular memory pools. Nevertheless, it is highly recommended to utilize DMA memory for any memory which is to be used in data transfers involving hardware, as it will make the code more easily portable to other chips.

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Function Documentation

dma_addr_t dma_pool_alloc

(

struct dma_pool *

pool

)

[inline, static]

Allocate an object from a DMA pool.

Parameters:

pool

The pool from which the object will be allocated

Definition at line 77 of file dmapool_nommu.h.

References mem_pool_alloc(), dma_pool::mempool, and dma_addr_t::ptr.

void dma_pool_free	(	struct dma_pool *	pool,
		dma_addr_t	addr
	)			[inline, static]

Free an object previously allocated from pool.

Warning:

If an object is freed into a different pool than the one from which it was allocated, or if the same object is freed multiple times, the DMA pool will get corrupted and subsequent allocations may return invalid objects or fail in other, unexpected ways.

Parameters:

	pool	The pool from which the object was allocated
	addr	The physical and virtual address of the object

Definition at line 87 of file dmapool_nommu.h.

References mem_pool_free(), dma_pool::mempool, and dma_addr_t::ptr.

void dma_pool_init_coherent	(	struct dma_pool *	pool,
		phys_addr_t	phys_start,
		size_t	size,
		size_t	objsize,
		unsigned int	align_order
	)			[inline, static]

Initialize a DMA-coherent memory pool.

This function will initialize a pool of fixed-size objects located in DMA-coherent memory. Since the memory is coherent, no cache synchronization is needed before and after DMA data transfers.

Parameters:

	pool	The DMA pool to be initialized
	phys_start	The physical address of the underlying memory area
	size	The size of the underlying memory area in bytes
	objsize	The size of each object in bytes
	align_order	log2 of the minimum object alignment in bytes

Definition at line 69 of file dmapool_nommu.h.

References mem_pool_init(), and dma_pool::mempool.

Referenced by dma_pool_init_coherent_physmem().

void dma_pool_init_coherent_physmem	(	struct dma_pool *	dmapool,
		struct physmem_pool *	phys_pool,
		unsigned int	nr_objects,
		size_t	objsize,
		unsigned int	align_order
	)

Initialize a DMA pool using the physmem allocator.

This function will grab enough physical memory for nr_objects from phys_pool and use this to initialize dmapool.

Parameters:

	dmapool	The DMA pool to be initialized.
	phys_pool	The physical memory pool from which to grab memory
	nr_objects	The number of objects in the pool
	objsize	The size of each object in bytes.
	align_order	log2 of the minimum object alignment in bytes.

Precondition:

nr_objects must be at least one.

There must be enough available memory in phys_pool.

objsize must be larger than the size of a pointer.

See also:

dma_pool_init()

Definition at line 67 of file dmapool.c.

References assert, dma_pool_init_coherent(), physmem_alloc(), PHYSMEM_ALLOC_ERR, and round_up.