On 2021-10-13 16:00, Robert Elz wrote:
Date: Tue, 12 Oct 2021 09:42:55 -0400
From: matthew sporleder <msporleder%gmail.com@localhost>
Message-ID: <CAHKF-AtpTrW_MnOq5WeB1njpzCuQBjcyexaM_X1LeEmXrjw=UQ%mail.gmail.com@localhost>
| Do you mean modem like a telephone modem or modem like a serial port?
I meant telephone modems - they're what most uses DTR as a functional
signal, and it is disabling that signal that all this is about. (There
were other devices that behaved similarly, but they're even less likely to
be seen now.)
The serial port is the system interface to the modem (that is the interface
in question - modems that are implemented on ISA/EISA/PCI/PCIe/... cards
are entirely different beasts, though I believe that some of those, probably
even most, present a system interface that looks like a serial port, and
most likely manipulating the fake DTR on that fake serial port would have
similar effects).
And yes, I know that these things are not quite as commonly used these
days as they were in the 1970's and 80's ...
Right. And the point of the DTR is that if it is dropped, then the modem is supposed to hang up the line. But this requires that the signal stays low for some amount of time, as modems or telephone lines weren't that fast to react.
And yeah, this might not be a common piece of hardware anymore, but I'm a bit unsure what the purpose/point of the change is.
Sure, if all serial port drivers were to implement this at close, then getty certainly could skip it. But the OP at the same time also question if people are using getty at all, in which case, what is the problem with the delay in getty in the first place?
And if the serial driver just don't allow a new open to complete until some defined time after the close, then an additional delay in getty don't really cause any problems at all.
Do we have any confidence that all serial drivers actually do enforce this delay at close? I'm thinking of stuff like VAXen here, which actually might have a few serial lines more or less all the time, as opposed to PCs, where I can believe it's not that common anymore.
Johnny
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|| on a psychedelic trip
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