Page Comparison

Creates a memory segmentAllocates memory from specified segment for a "hardware buffer" (a buffer that can be accessed via a DMA engine). The returned buffer will be padded in function of memory segment's properties.

Files

lib_mem.h/lib_mem.c

Prototype

          void  *Mem_SegCreateSegAllocHW (const  CPU_CHAR    *p_name,
	   
                              MEM_SEG     *p_seg,
     
                                CPU_ADDRSIZE_T     seg_base_addrsize,
                                      CPU_SIZE_T   size,
       align,
                              CPU_SIZE_T   padding_align,
      *p_bytes_reqd,
                               LIB_ERR     *p_err);

Arguments

p_name

Pointer to segment nameallocated object name. Used for allocations tracking. May be DEF_NULL.

p_seg

Pointer to segment data. Must be allocated by caller.

seg_base_addr

Address of segment's first byte.from which to allocate memory.

size

Total size of segmentSize of memory block to allocate, in bytes.

padding_align

Padding Required alignment of memory block, in bytes, that will be added to any allocated buffer from this memory segment. MUST be a power of 2. LIB

p_

...

bytes_reqd

Pointer to variable that will receive the number of free bytes missing for the allocation to succeed. Set to DEF_NULL to skip calculation.

p_err

Pointer to variable that will receive the return error code from this function.

LIB_MEM_ERR_NONE

LIB_MEM_ERR_INVALID_SEGMEM_SIZE

LIB_MEM_ERR_INVALID_MEM_ALIGN

LIB_MEM_ERR_NULL_PTR

LIB_MEM_ERR_INVALID_SEG_OVERLAP

LIB_MEM_ERR_INVALID_SEG_EXISTS

Returned Value

...

OVF

Returned Value

Pointer to allocated memory block, if successful.

DEF_NULL, otherwise.

Required Configuration

None.

Notes / Warnings

1. New segments are checked for overlap with existing segments. A critical section needs to be maintained during the whole list search and add procedure to prevent a reentrant call from creating another segment overlapping with the one being addedThe buffer returned by this function will be padded according to the padding_align argument passed at creation of this memory segment. This is particularly useful with systems that use cache memory and DMA engine to copy buffers as it guarantees that nothing else will be allocated on the same cache line (as long as the padding_align argument is set to the length of a cache line).
2. For an usage example of this function, refer to Memory Segments page.