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Subject[PATCH 1/2] Introduce tty_unregister_ldisc()
Date
It's a bit strange to see tty_register_ldisc call in modules' exit functions.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
---
Documentation/tty.txt | 2 +-
drivers/char/tty_io.c | 35 ++++++++++++++++++++++++-----------
include/linux/tty.h | 1 +
3 files changed, 26 insertions(+), 12 deletions(-)
diff -uprN linux-tty_register_ldisc_000/Documentation/tty.txt linux-tty_register_ldisc_001/Documentation/tty.txt
--- linux-tty_register_ldisc_000/Documentation/tty.txt 2005-05-31 20:12:47.000000000 +0400
+++ linux-tty_register_ldisc_001/Documentation/tty.txt 2005-05-31 23:19:32.000000000 +0400
@@ -22,7 +22,7 @@ copy of the structure. You must not re-r
discipline even with the same data or your computer again will be eaten by
demons.

-In order to remove a line discipline call tty_register_ldisc passing NULL.
+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.
diff -uprN linux-tty_register_ldisc_000/drivers/char/tty_io.c linux-tty_register_ldisc_001/drivers/char/tty_io.c
--- linux-tty_register_ldisc_000/drivers/char/tty_io.c 2005-05-31 20:13:34.000000000 +0400
+++ linux-tty_register_ldisc_001/drivers/char/tty_io.c 2005-05-31 23:17:40.000000000 +0400
@@ -262,17 +262,10 @@ int tty_register_ldisc(int disc, struct
return -EINVAL;

spin_lock_irqsave(&tty_ldisc_lock, flags);
- if (new_ldisc) {
- tty_ldiscs[disc] = *new_ldisc;
- tty_ldiscs[disc].num = disc;
- tty_ldiscs[disc].flags |= LDISC_FLAG_DEFINED;
- tty_ldiscs[disc].refcount = 0;
- } else {
- if(tty_ldiscs[disc].refcount)
- ret = -EBUSY;
- else
- tty_ldiscs[disc].flags &= ~LDISC_FLAG_DEFINED;
- }
+ tty_ldiscs[disc] = *new_ldisc;
+ tty_ldiscs[disc].num = disc;
+ tty_ldiscs[disc].flags |= LDISC_FLAG_DEFINED;
+ tty_ldiscs[disc].refcount = 0;
spin_unlock_irqrestore(&tty_ldisc_lock, flags);

return ret;
@@ -280,6 +273,26 @@ int tty_register_ldisc(int disc, struct

EXPORT_SYMBOL(tty_register_ldisc);

+int tty_unregister_ldisc(int disc)
+{
+ unsigned long flags;
+ int ret = 0;
+
+ if (disc < N_TTY || disc >= NR_LDISCS)
+ return -EINVAL;
+
+ spin_lock_irqsave(&tty_ldisc_lock, flags);
+ if (tty_ldiscs[disc].refcount)
+ ret = -EBUSY;
+ else
+ tty_ldiscs[disc].flags &= ~LDISC_FLAG_DEFINED;
+ spin_unlock_irqrestore(&tty_ldisc_lock, flags);
+
+ return ret;
+}
+
+EXPORT_SYMBOL(tty_unregister_ldisc);
+
struct tty_ldisc *tty_ldisc_get(int disc)
{
unsigned long flags;
diff -uprN linux-tty_register_ldisc_000/include/linux/tty.h linux-tty_register_ldisc_001/include/linux/tty.h
--- linux-tty_register_ldisc_000/include/linux/tty.h 2005-05-31 20:15:51.000000000 +0400
+++ linux-tty_register_ldisc_001/include/linux/tty.h 2005-05-31 23:18:23.000000000 +0400
@@ -345,6 +345,7 @@ extern int tty_check_change(struct tty_s
extern void stop_tty(struct tty_struct * tty);
extern void start_tty(struct tty_struct * tty);
extern int tty_register_ldisc(int disc, struct tty_ldisc *new_ldisc);
+extern int tty_unregister_ldisc(int disc);
extern int tty_register_driver(struct tty_driver *driver);
extern int tty_unregister_driver(struct tty_driver *driver);
extern void tty_register_device(struct tty_driver *driver, unsigned index, struct device *dev);
-
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