mirror of https://github.com/nirenjan/libx52.git
35 lines
1.4 KiB
Markdown
35 lines
1.4 KiB
Markdown
LibUSB X52 stub library
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=======================
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The libusbx52 stub library is a convenience library to help test the libusb
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functions used by libx52 and associated code. It simulates the behavior of the
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libusb functions used by the libx52 library, but doesn't actually control any
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real hardware, and simply updates a few in-memory data structures.
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The idea behind `libusbx52.so` is to use it as an LD_PRELOAD library, where it
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will override the real functions used by `libx52.so`. The use case for this
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scenario is in an automated testing environment, where a test runner could set
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up the list of devices manually and simulate various scenarios.
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# Design Overview
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The build system does not wire up `LD_PRELOAD` for this library: using it is
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left to the test runner, which must arrange for the stub to be preloaded and
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control the data passed between processes.
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# Data Structures
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The server process is responsible for setting up the initial set of USB devices.
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As far as libx52 is concerned, the only fields that it uses in the USB
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descriptor are the idVendor and idProduct fields. These are written to a file
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that is read by the libusbx52 stubs to populate the device list.
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Once the file has been written by the server, the libusb_init stub function in
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the client can read the file and populate the internal data structures as
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necessary.
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The client can also write to a separate file to record the USB communication
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sent across to the simulated device.
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