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Missed one file in last checking; Gran allocator alignment decoupled from granule size

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git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@5152 42af7a65-404d-4744-a932-0658087f49c3
This commit is contained in:
patacongo
2012-09-14 18:14:40 +00:00
parent 6672fa6ff6
commit a5f05e3e5b
2 changed files with 99 additions and 19 deletions
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include/nuttx/gran.h
+35 -6
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@@ -90,9 +90,32 @@ extern "C" {
*
* Description:
* Set up one granule allocator instance. Allocations will be aligned to
* the granule size; allocations will be in units of the granule size.
* Larger granules will give better performance and less overhead but more
* losses of memory due to alignment and quantization waste.
* the alignment size (log2align; allocations will be in units of the
* granule size (log2gran). Larger granules will give better performance
* and less overhead but more losses of memory due to alignment
* quantization waste. Additional memory waste can occur form alignment;
* log2align should be set to 0 unless you are using the granule allocator
* to manage DMA memory and your hardware has specific memory alignment
* requirements.
*
* Geneneral Usage Summary. This is an example using the GCC section
* attribute to position a DMA heap in memory (logic in the linker script
* would assign the section .dmaheap to the DMA memory.
*
* FAR uint32_t g_dmaheap[DMAHEAP_SIZE] __attribute__((section(.dmaheap)));
*
* The heap is created by calling gran_initialize. Here the granual size
* is set to 64 bytes and the alignment to 16 bytes:
*
* GRAN_HANDLE handle = gran_initialize(g_dmaheap, DMAHEAP_SIZE, 6, 4);
*
* Then the GRAN_HANDLE can be used to allocate memory (There is no
* GRAN_HANDLE if CONFIG_GRAN_SINGLE=y):
*
* FAR uint8_t *dma_memory = (FAR uint8_t *)gran_alloc(handle, 47);
*
* The actual memory allocates will be 64 byte (wasting 17 bytes) and
* will be aligned at least to (1 << log2align).
*
* NOTE: The current implementation also restricts the maximum allocation
* size to 32 granules. That restriction could be eliminated with some
@@ -102,7 +125,13 @@ extern "C" {
* heapstart - Start of the granule allocation heap
* heapsize - Size of heap in bytes
* log2gran - Log base 2 of the size of one granule. 0->1 byte,
* 1->2 bytes, 2->4 bytes, 3-> 8bytes, etc.
* 1->2 bytes, 2->4 bytes, 3-> 8 bytes, etc.
* log2align - Log base 2 of required alignment. 0->1 byte,
* 1->2 bytes, 2->4 bytes, 3-> 8 bytes, etc. Note that
* log2gran must be greater than or equal to log2align
* so that all contiguous granules in memory will meet
* the minimum alignment requirement. A value of zero
* would mean that no alignment is required.
*
* Returned Value:
* On success, a non-NULL handle is returned that may be used with other
@@ -112,10 +141,10 @@ extern "C" {
#ifdef CONFIG_GRAN_SINGLE
EXTERN int gran_initialize(FAR void *heapstart, size_t heapsize,
uint8_t log2gran);
uint8_t log2gran, uint8_t log2align);
#else
EXTERN GRAN_HANDLE gran_initialize(FAR void *heapstart, size_t heapsize,
uint8_t log2gran);
uint8_t log2gran, uint8_t log2align);
#endif
/****************************************************************************