chan_simpleusb, chan_usbradio: nonblocking pttkick pipe.

[mkmer]

Summary by CodeRabbit

• Bug Fixes
  • Improved I/O handling by ensuring pipes are created in non-blocking mode from the start, preventing potential blocking issues during operation.

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📝 Walkthrough

Walkthrough

Both USB channel driver implementations update their HID thread initialization to create the PTT kick pipe using pipe2 with the O_NONBLOCK flag instead of the standard pipe() call. Error handling and thread lifecycle remain unchanged.

Changes

PTT Pipe Non-blocking I/O

Layer / File(s)	Summary
Non-blocking PTT pipe initialization in HID threads channels/chan_simpleusb.c, channels/chan_usbradio.c	Both HID threads switch from pipe() to pipe2(..., O_NONBLOCK) for creating the pttkick pipe, ensuring non-blocking file descriptors from creation. Error paths log and exit the thread on failure without change.

🎯 1 (Trivial) | ⏱️ ~3 minutes

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately and concisely describes the main change: converting the pttkick pipe to non-blocking mode in both chan_simpleusb and chan_usbradio files.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch pttkick-non-blocking

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Actionable comments posted: 2

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@channels/chan_simpleusb.c`:
- Line 1112: The pttkick pipe is opened non-blocking (pipe2(o->pttkick,
O_NONBLOCK)) but both kickptt() (writer) and the pttkick read handler treat res
<= 0 as fatal; change both to ignore expected non-blocking conditions by
checking errno: in kickptt() when write returns -1, if errno is EAGAIN or
EWOULDBLOCK simply return/skip without logging an error, and in the pttkick read
handler (around the current read at ~line 1161) when read returns -1, if errno
is EAGAIN or EWOULDBLOCK do not treat it as an error (just return/continue);
keep other error/EOF handling unchanged.

In `@channels/chan_usbradio.c`:
- Line 1084: The non-blocking pipe created with pipe2(o->pttkick, O_NONBLOCK)
requires kickptt() to treat EAGAIN/EWOULDBLOCK as benign backpressure rather
than a hard error; update the write() error handling inside kickptt() to check
errno and only log/handle true failures, while silently ignoring or returning
success on errno == EAGAIN || errno == EWOULDBLOCK (and keep existing handling
for other errno values), and ensure the code references o->pttkick and the
kickptt() function when making this change so the non-blocking behavior is
correctly honored.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

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Configuration used: Path: .coderabbit.yaml

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📥 Commits

Reviewing files that changed from the base of the PR and between ce55d4b and bcfc13b.

📒 Files selected for processing (2)

• channels/chan_simpleusb.c
• channels/chan_usbradio.c

[mkmer]

We "could" block on the write side if something slows down the read side. Since we are polling, we really should never fail to read in the hidthread().