# AWS EC2 FPGA SDK Userspace Software

The [Programmer's View](../../hdk/docs/Programmer_View.md) describes all the runtime software components that would be used in an FPGA-enabled EC2 instance like F1. It supports linux operating systems only.

This directory contains the source and build files for the needed components:

1. The [fpga_mgmt_tools directory](./fpga_mgmt_tools) contains  [Amazon FPGA Image (AFI) Management Tools](./fpga_mgmt_tools/README.md): A linux shell commands to manage AFI, Virtual JTAG, Virtual LED and DIPSwitches. Calling [`sdk_setup.sh`](../../sdk_setup.sh) will compile and install the tools.

2. The [Include directory](./include) contains the header files required for integration with a C/C++ application.

3. The [FPGA Libraries](./fpga_libs) contains source files for fpga_pci and fpga_mgmt libraries: libraries used to integrate with C/C++ applications, and need to be compiled and statically linked with the C/C++ applications. The [CL Examples](../../hdk/cl/examples) have example applications builds that use these libraries.

4. The [Utility](./utils) contains source files for various utilities used by the fpga_libs and fpga_mgmt_tools, like logging services.

### Note about readdir and FPGA libraries

In recent versions of glibc, `readdir_r` (a reentrant version of `readdir`) was marked as deprecated in favor of `readdir`. However, `readdir` is not guaranteed to be threadsafe. The library uses a `pthread_mutex_t` to ensure that only one thread at a time can invoke readdir.  The `fpga_mgmt` library also exports this mutex to make it possible for code which links to this library to protect any calls to readdir. See [`fpga_pci.h`](./include/fpga_pci.h) for more information.