uart: Support EARLY_PRINTF on x86 for port-mapped COM ports
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Authored by imp on Oct 19 2023, 6:26 PM.

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emaste

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rGa113f9dd9886: uart: Support EARLY_PRINTF on x86 for port-mapped COM ports

Summary

Support early printf for the ns8250 uart driver. Adding
options UART_NS8250_EARLY_PORT=0xYYY
options EARLY_PRINTF
to your kernel config will enable it. The code is rather simple minded,
so caveat emptor. This will enable printf before cninit. cninit
automatically disables this and switches to the real routine. It only
works for port-mapped COM ports, and only if you know the port's address
at compile time. It's intended for be a debugging aide, not a general
purpose thing.

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rG FreeBSD src repository

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Build Status

Buildable 54100
Build 50990: arc lint + arc unit

Event Timeline

imp requested review of this revision.Oct 19 2023, 6:26 PM

imp created this revision.

Harbormaster completed remote builds in B54100: Diff 129126.Oct 19 2023, 6:26 PM

emaste added a subscriber: emaste.Oct 20 2023, 1:29 PM

emaste added inline comments.Oct 20 2023, 1:31 PM

sys/conf/options
665	a comment that it's x86-only?
sys/dev/uart/uart_dev_ns8250.c
91	`u_int` to match inb/outb?

make more x86 specific and clear that it's x86 specific so it doesn't interfere
on other architectures. Opted to do that vs #ifdefing based on
UART_NS8250_EARLY_PORT being defined.

Harbormaster completed remote builds in B54111: Diff 129157.Oct 20 2023, 2:34 PM