xiaoxiang781216 opened a new pull request, #19184:
URL: https://github.com/apache/nuttx/pull/19184
## Summary
Add lightweight job-control/controlling-terminal support for serial and PTY
drivers on systems without a real POSIX session/process-group model.
NuttX currently treats each task as its own process group. This patch keeps
that model (`pgrp == pid`) and adds the missing APIs/ioctls needed by portable
software such as dropbear/socat:
- Add `TIOCGPGRP`, `TIOCSPGRP`, and `TIOCGSID` ioctl numbers.
- Extend `serial.c` and `pty.c` to support:
- `TIOCSCTTY`: `arg > 0` preserves the existing NuttX convention of
passing an explicit target PID (used by NSH for foreground commands), while
`arg == 0` follows POSIX-style flag semantics and selects the calling task.
- `TIOCGPGRP` / `TIOCGSID`: return the current foreground PID.
- `TIOCSPGRP`: set the foreground PID (or caller when pgrp is zero).
- Add libc wrappers:
- `tcgetpgrp()`, `tcsetpgrp()`, `tcgetsid()` over the new ioctls.
- `setsid()`, `getsid()`, `setpgid()` stubs consistent with the existing
single-member process-group model.
- Document the behavior and limitations in
`Documentation/components/drivers/character/serial.rst`.
## Rationale
This avoids regressing existing NSH behavior where `TIOCSCTTY` is used to
register a spawned foreground command as the Ctrl-C/Ctrl-Z signal target, while
also supporting the POSIX-style `ioctl(fd, TIOCSCTTY, 0)` pattern used by
dropbear and similar software.
Group-broadcast signaling (`kill(-pgrp, signo)`) remains unsupported, so
TTY-generated signals still target a single foreground PID.
## Testing
- `git diff apache/master..HEAD | ./tools/checkpatch.sh -` completed
successfully. The script reports only that `cmake-format` is not installed in
this environment.
- Cherry-picked cleanly onto current `apache/master` after resolving
declaration/list-order conflicts with upstream `gettid()` / unistd Make.defs
changes.
A full `sim:nsh` build could not be completed from this local workspace
because the checked-out `apps/` tree is not an upstream-compatible apps tree
(`apps/examples/Kconfig` is missing). The patch itself is confined to NuttX
serial/libc code and documentation.
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