Replace tty0tty with a USB/IP CP2102 simulator - #121
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GitHub's Azure kernels ship no USB serial drivers, so the emulated CP2102 had nothing to bind to. Build usbserial and cp210x out of tree from the matching upstream sources, and build the emulator once per push instead of once per Python version.
… the simulation per USB frame
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Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## dev #121 +/- ##
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+ Coverage 93.11% 94.13% +1.01%
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Files 24 24
Lines 4025 4025
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+ Hits 3748 3789 +41
+ Misses 277 236 -41 ☔ View full report in Codecov by Harness. 🚀 New features to boost your workflow:
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I was researching USB/IP and realized something interesting: USB/IP allows real kernel drivers to attach to fake devices exposed by userspace tools. For serialx, this allows reasonably-accurate simulation of serial hardware and lets us improve on both tty0tty and com0com.
Kernel modules like tty0tty cover the 99% use case of virtual serial ports that only need to shuttle data through a serial-ish pipe, there's no reason to be "accurate". For serialx, however, we ideally want something that behaves like a real pair of adapters connected end-to-end:
As it turns out, this is very straightforward to implement by allowing the real
cp210xkernel driver to attach to a pair of emulated USB devices connected over loopback USB/IP. The fake USB devices show up in/dev/serial/by-id/with proper metadata and pass the entire serialx test suite. All of the tty0tty test suite quirks for Linux have been removed:no-rts-cts,no-dtr-dsr,no-num-unwritten-bytes,no-reset-write-buffer,no-write-timeout,no-buffer-controlbecomes justno-reset-write-buffer.