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| -rw-r--r-- | Documentation/tty/tty_ldisc.rst | 39 |
1 files changed, 19 insertions, 20 deletions
diff --git a/Documentation/tty/tty_ldisc.rst b/Documentation/tty/tty_ldisc.rst index 8e48ab72f965..69dee9ca6540 100644 --- a/Documentation/tty/tty_ldisc.rst +++ b/Documentation/tty/tty_ldisc.rst @@ -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 +Registration +============ + +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(). -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. +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). + +.. kernel-doc:: drivers/tty/tty_ldisc.c + :identifiers: tty_register_ldisc tty_unregister_ldisc -Line Discipline Methods -======================= +Line Discipline Operations Reference +==================================== .. kernel-doc:: include/linux/tty_ldisc.h :identifiers: tty_ldisc_ops |