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Re: term & user space console
From: |
Thomas Bushnell, BSG |
Subject: |
Re: term & user space console |
Date: |
18 Dec 2001 13:44:08 -0800 |
User-agent: |
Gnus/5.0808 (Gnus v5.8.8) Emacs/20.7 |
tb@becket.net (Thomas Bushnell, BSG) writes:
> > The pty interface does also not handle START and STOP. It stores
> > the state in flags, but it does not make use of it in any way.
>
> That's a bug.
There should be no bug here. Output happens under the control of
pty_io_read, and it does in fact check USER_OUTPUT_SUSP; if the flag
is set, then it doesn't allow the read to continue.
> It's really the responsibility of the bottom handler. For START and
> STOP, it's important to use the underlying filesystem *if* it
> implements the calls, otherwise, just do it in the bottom handler.
> (The reason is that buffering may be going on further down.) I would
> suggest trying the appropriate ioctl calls; if they fail, then do it
> in the bottom handler. Probably the same strategy should be used for
> Mach devices.
Ok, what I wrote here was confusing and wrong.
For START and STOP, the deal is that the upper half sets
USER_SUSPEND_OUTPUT, and calls suspend_physical_output. That function
should, if needed, set a local bit (called "output_stopped" in the
existing drivers) and also tell the underlying thing to try and stop
output. The start_output function (and wherever else) are responsible
for making sure that if USER_SUSPEND_OUTPUT is set, no output happens.
- term & user space console, Marcus Brinkmann, 2001/12/17
- Re: term & user space console, Thomas Bushnell, BSG, 2001/12/18
- Re: term & user space console,
Thomas Bushnell, BSG <=
- Re: term & user space console, Thomas Bushnell, BSG, 2001/12/18
- Re: term & user space console, Roland McGrath, 2001/12/19