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tty: make tty_ldisc docs up-to-date

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Some of the docs in this document were a bit obsolete. Clean it up a bit
and make it correspond to the current state.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20211126081611.11001-21-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Jiri Slaby 2021-11-26 09:16:08 +01:00 committed by Greg Kroah-Hartman
parent 7e6c0b22f4
commit 6f05358661
1 changed files with 19 additions and 20 deletions
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39
Documentation/tty/tty_ldisc.rst
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@ -6,31 +6,30 @@ TTY Line Discipline
.. contents:: :local:
Line disciplines are registered with tty_register_ldisc() passing the
discipline number and the ldisc structure. At the point of registration the
discipline must be ready to use and it is possible it will get used before
the call returns success. If the call returns an error then it won't get
called. Do not re-use ldisc numbers as they are part of the userspace ABI
and writing over an existing ldisc will cause demons to eat your computer.
After the return the ldisc data has been copied so you may free your own
copy of the structure. You must not re-register over the top of the line
discipline even with the same data or your computer again will be eaten by
demons.
Registration
============
In order to remove a line discipline call tty_unregister_ldisc().
In ancient times this always worked. In modern times the function will
return -EBUSY if the ldisc is currently in use. Since the ldisc referencing
code manages the module counts this should not usually be a concern.
Line disciplines are registered with tty_register_ldisc() passing the ldisc
structure. At the point of registration the discipline must be ready to use and
it is possible it will get used before the call returns success. If the call
returns an error then it won’t get called. Do not re-use ldisc numbers as they
are part of the userspace ABI and writing over an existing ldisc will cause
demons to eat your computer. You must not re-register over the top of the line
discipline even with the same data or your computer again will be eaten by
demons. In order to remove a line discipline call tty_unregister_ldisc().
Heed this warning: the reference count field of the registered copies of the
tty_ldisc structure in the ldisc table counts the number of lines using this
discipline. The reference count of the tty_ldisc structure within a tty
counts the number of active users of the ldisc at this instant. In effect it
counts the number of threads of execution within an ldisc method (plus those
about to enter and exit although this detail matters not).
discipline. The reference count of the tty_ldisc structure within a tty counts
the number of active users of the ldisc at this instant. In effect it counts
the number of threads of execution within an ldisc method (plus those about to
enter and exit although this detail matters not).
Line Discipline Methods
=======================
.. kernel-doc:: drivers/tty/tty_ldisc.c
:identifiers: tty_register_ldisc tty_unregister_ldisc
Line Discipline Operations Reference
====================================
.. kernel-doc:: include/linux/tty_ldisc.h
:identifiers: tty_ldisc_ops