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Subjectdynamic pty driver...
I'm working on a dynamic pty driver.  The purpose being to allow the
creation of ptys by normal users (no more suid root screen!) and to allow
the creation of an almost unlimited number of ptys without wasting a bunch
of RAM for huge arrays on small systems or trying to switch to 16-bit minors
or anything like that. The ptys would not have associated files/devices and
they'd be made using a syscall similar to pipe() (should I make a new
syscall or just an ioctl()?). Another possibility would be to add another
filetype for mknod(), S_IFPTY that normal users could create, but this
doesn't seem reasonable to me and I am unlikely to bother to implement it.
It would be trivial to modify rxvt, screen, etc. to use these instead of
/dev/pty* and /dev/tty[p-za-e]?.

It looks like the best way to do this is to make a different
tty_driver struct for every pty. I'm not sure what major/minor to give
them...I was thinking I could probably just make all of them 5,0 (/dev/tty),
but this would cause ps to see 5,0 as the tty device in /proc/<pid>/stat so
it would list all processes on dptys as being run on /dev/tty...not the most
useful solution. I was also considering possibly not adding the tty_driver
structs to the actual tty_driver linked list. All the tables would be
dynamically allocated with the tty_driver struct and would be created with
only one entry.

I was just wondering if anyone had any comments, suggestions, etc.,
before I go implementing (I haven't done much deep kernel hacking in the
past and the whole tty layout is just now beginning to somewhat make a
little sense).

FYI, this idea is not my own but was suggested to me by Alan Cox (I
think...it's been a while).

Greg Alexander - also <gralexan@indiana.edu> - http://sietch.home.ml.org/
----
"People are very flexible and learn to adjust to strange
surroundings -- they can become accustomed to read Lisp and
Fortran programs, for example."
-- Leon Sterling and Ehud Shapiro, Art of Prolog, MIT Press

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