[PATCH] tty layer comment the locking assumptions and functions somewhat

Doesn't fix them but does show up some interesting areas that need review
and fixing.

Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 57 insertions, 2 deletions

diff --git a/drivers/char/tty_ioctl.c b/drivers/char/tty_ioctl.c
index f19cf9d7792d..4ad47d321bd4 100644
--- a/drivers/char/tty_ioctl.c
+++ b/drivers/char/tty_ioctl.c
@@ -36,6 +36,18 @@
 #define TERMIOS_WAIT    2
 #define TERMIOS_TERMIO  4
 
+
+/**
+ *      tty_wait_until_sent     -       wait for I/O to finish
+ *      @tty: tty we are waiting for
+ *      @timeout: how long we will wait
+ *
+ *      Wait for characters pending in a tty driver to hit the wire, or
+ *      for a timeout to occur (eg due to flow control)
+ *
+ *      Locking: none
+ */
+
 void tty_wait_until_sent(struct tty_struct * tty, long timeout)
 {
         DECLARE_WAITQUEUE(wait, current);
@@ -94,6 +106,18 @@ static void unset_locked_termios(struct termios *termios,
                         old->c_cc[i] : termios->c_cc[i];
 }
 
+/**
+ *      change_termios          -       update termios values
+ *      @tty: tty to update
+ *      @new_termios: desired new value
+ *
+ *      Perform updates to the termios values set on this terminal. There
+ *      is a bit of layering violation here with n_tty in terms of the
+ *      internal knowledge of this function.
+ *
+ *      Locking: termios_sem
+ */
+
 static void change_termios(struct tty_struct * tty, struct termios * new_termios)
 {
         int canon_change;
@@ -155,6 +179,19 @@ static void change_termios(struct tty_struct * tty, struct termios * new_termios
         up(&tty->termios_sem);
 }
 
+/**
+ *      set_termios             -       set termios values for a tty
+ *      @tty: terminal device
+ *      @arg: user data
+ *      @opt: option information
+ *
+ *      Helper function to prepare termios data and run neccessary other
+ *      functions before using change_termios to do the actual changes.
+ *
+ *      Locking:
+ *              Called functions take ldisc and termios_sem locks
+ */
+
 static int set_termios(struct tty_struct * tty, void __user *arg, int opt)
 {
         struct termios tmp_termios;
@@ -284,6 +321,17 @@ static void set_sgflags(struct termios * termios, int flags)
         }
 }
 
+/**
+ *      set_sgttyb              -       set legacy terminal values
+ *      @tty: tty structure
+ *      @sgttyb: pointer to old style terminal structure
+ *
+ *      Updates a terminal from the legacy BSD style terminal information
+ *      structure.
+ *
+ *      Locking: termios_sem
+ */
+
 static int set_sgttyb(struct tty_struct * tty, struct sgttyb __user * sgttyb)
 {
         int retval;
@@ -369,9 +417,16 @@ static int set_ltchars(struct tty_struct * tty, struct ltchars __user * ltchars)
 }
 #endif
 
-/*
- * Send a high priority character to the tty.
+/**
+ *      send_prio_char          -       send priority character
+ *
+ *      Send a high priority character to the tty even if stopped
+ *
+ *      Locking: none
+ *
+ *      FIXME: overlapping calls with start/stop tty lose state of tty
  */
+
 static void send_prio_char(struct tty_struct *tty, char ch)
 {
         int     was_stopped = tty->stopped;