tcflow(TCOON/TCOOFF) vs. received XON/XOFF characters

[Grant Edwards <grant.b.edwards@gmail.com>]

I'm working on the regression test appliction I use to test the serial
drivers I maintain, and I've run into a problem with interaction
between tcflow(TCOON/TCOOFF) and XON/XOFF using bog-standard 16x50
UARTs and the normal in-kernel driver.

When I call tcflow(TCOOFF) on a tty device and then write data to that
tty device, the data isn't sent. That's what I expect. But, when an
XON is then received by that port, it does not start the tx data.

Conversly, when a serial port receives an XOFF, it stops sending
data as it should, but a subsequent call to tcflow(TCOON) does not
casue it to start sending data.

Am I misunderstanding how tcflow(TCOxxx) is supposed to interact with
XON/XOFF flow control?

Or is something broken in the tty layer or uart driver?

-- 
Grant Edwards               grant.b.edwards        Yow! This is a NO-FRILLS
                                  at               flight -- hold th' CANADIAN
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