Hardware Function Call Guidelines

Stub functions generated in the SDSoC™ environment transfer the exact number of bytes according the compile-time determinable array bound of the corresponding argument in the hardware function declaration. If a hardware function admits a variable data size, you can use the following pragma to direct the SDSoC environment to generate code to transfer data whose size is defined by an arithmetic expression:
```
#pragma SDS data copy|zero_copy(arg[0:]) #pragma SDS data zero_copy(arg[0:])
```
where themust compile in the scope of the function declaration.
Thezero_copypragma directs the SDSoC environment to map the argument into shared memory.
Be aware that mismatches between intended and actual data transfer sizes can cause the system to hang at runtime, requiring laborious hardware debugging.
Align arrays transferred by DMAs on cache-line boundaries (for L1 and L2 caches). Use thesds_alloc()API provided with the SDSoC environment instead ofmalloc()to allocate these arrays.
Align arrays to page boundaries to minimize the number of pages transferred with the scatter-gather DMA, for example, for arrays allocated withmalloc.
You must usesds_allocto allocate an array for the following two cases:
1. You are using zero-copy pragma for the array.
2. You are using pragmas to explicitly direct the system compiler to use Simple-DMA.
Note that in order to usesds_alloc()fromsds_lib.h, it is necessary to includestdlib.hbefore includingsds_lib.h.stdlib.his included to provide thesize_ttype.