Re: netfs part of a console server with server-client model

[Marcus Brinkmann]

On Sun, Jun 02, 2002 at 11:37:05PM +0200, Niels Möller wrote:
> Ooops, the term server is in the way as well. I just think that it
> would be nice to have a clean way to get from the tty to the raw
> display, preferably without too much knowledge about the layout of the
> directories provided by the console server.

Well, this is something that can be added easily at any time.  Even if you
have to restructure the directory layout, it is localised to a few functions
and structures in the code, so I am willing to punt this off until a real
need arises.
 
> Having all these little servers stacked on each other makes me think
> of STREAMS (with which I don't have much experience).

I don't know STREAMS, but having all these little servers stacked makes me
think of performance :)  A key stroke will go from the kernel to the input
device to the console server to the term server to the application and
echoed to the console server to the display device.  This includes a couple
of conversions (from scan code to UCS-4 to local encoding and from local
encoding back to UCS-4 and to the encoding used by the display driver) and
one notification message (for the asynchronous display device interface).

Eg, let's say 4 or 5 more RPCs per key stroke, and the same amount of
context switches.  I am not sure what the impact will be, but of course with
the client-server model things like collecting small changes into a single
notification message etc become possible and possibly interesting.  We will
have to see about that when it works.

> And the problem is, given a port to one end of such a stack, you want
> to send an rpc to some server further down, and get the result back.
> Performing a dir-lookup on the console, given only a term conencted to
> the console, is one example.

I am more interested in learning about possible uses of this interface
rather than the implementation details.  Do you know about any particular
program that needs this (eg one that doesn't talk directly to term?).
It can not be a portable program, it must use something like /dev/vcsa in
the Linux kernel.

I know one such program, it is btty the braille terminal driver.  But this
is on the display driver end of our equation, and not on the application
using tty end.

Thanks,
Marcus

-- 
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Marcus Brinkmann              GNU    http://www.gnu.org    marcus@gnu.org
Marcus.Brinkmann@ruhr-uni-bochum.de
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