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okramer's avatar
okramer
Icon for Occasional Contributor rankOccasional Contributor
6 years ago

Host Pipes not working as documented in Programming Guide

Section 5.5.6.4 of the OpenCL FPGA Programming Guide has in the host code example a direct call to clReadPipeIntelFPGA() and clWritePipeIntelFPGA(), while the only downloadable code example (that I know of) that shows host pipes, "loopback_hostpipe", does the following:

map_pipe_fn = (void * (*) (cl_mem, cl_map_flags, size_t, size_t *, cl_int *)) clGetExtensionFunctionAddress("clMapHostPipeIntelFPGA");
   unmap_pipe_fn = (cl_int (*) (cl_mem, void *, size_t, size_t *)) clGetExtensionFunctionAddress("clUnmapHostPipeIntelFPGA");

So I tried modifying my host pipe code to use the same clGetExtensionFunctionAddress to access the clReadPipeIntelFPGA and clWritePipeIntelFPGA and that worked -- well, sort of -- at least it didn't hang like when I was calling clWritePipeIntelFPGA directly.

Is it a requirement to use clGetExtensionFunctionAddress to fetch those functions? Or should I be able to call clWritePipeIntelFPGA directly? Also, clGetExtensionFunctionAddress is marked as deprecated in cl.h, so obviously there's a better way to do it.

2 Replies

  • MEIYAN_L_Intel's avatar
    MEIYAN_L_Intel
    Icon for Frequent Contributor rankFrequent Contributor
    6 years ago

    Hi,

    I had reviewed the problem stated.

    According to https://www.intel.com/content/dam/www/programmable/us/en/pdfs/literature/hb/opencl-sdk/aocl_programming_guide.pdf in chapter 6.4 stated: " when you link your host application to the FPGA Client Driver (FCD), you cannot directly reference these Custom Platformspecific functions. To reference Custom Platform-specific user-accessible functions while linking to the FCD, include the clGetBoardExtensionFunctionAddressIntelFPGA extension in your host application".

    It seems like the function " clGetBoardExtensionFunctionAddressIntelFPGA" is used to point the function which is not specified in OpenCL Specification 2.0: https://www.khronos.org/registry/OpenCL/specs/opencl-2.0.pdf in chapter 5.4. Since the function eg: clReadPipeIntelFPGA, clWritePipeIntelFPGA, clMapHostPipeIntelFPGA, and clUnmapHostPipeIntelFPGA is not specified in OpenCL Specification, thus it need the function " clGetBoardExtensionFunctionAddressIntelFPGA" to point out the function.

    Also, I had reviewed the cl.h file. Since clGetBoardExtensionFunctionAddress is deprecated, it should be replace by another function with different name. I am not sure whether it is replaced "clGetBoardExtensionFunctionAddressIntelFPGA". But there is no " clGetBoardExtensionFunctionAddressIntelFPGA" is stated in the file. I have to check internally with the developer again. I will reply here once the developer reply to me.

    Thanks.