tty: rework break handling

Some hardware needs to do break handling itself and may have partial
support only. Make break_ctl return an error code. Add a tty driver flag
so you can indicate driver hardware side break support.

Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 12 insertions, 2 deletions

diff --git a/include/linux/tty_driver.h b/include/linux/tty_driver.h
index d2a003586761..e1065ac0d922 100644
--- a/include/linux/tty_driver.h
+++ b/include/linux/tty_driver.h
@@ -135,7 +135,7 @@
  *
  *      Optional:
  *
- * void (*break_ctl)(struct tty_stuct *tty, int state);
+ * int (*break_ctl)(struct tty_stuct *tty, int state);
  *
  *      This optional routine requests the tty driver to turn on or
  *      off BREAK status on the RS-232 port.  If state is -1,
@@ -146,6 +146,10 @@
  *      handle the following ioctls: TCSBRK, TCSBRKP, TIOCSBRK,
  *      TIOCCBRK.
  *
+ *      If the driver sets TTY_DRIVER_HARDWARE_BREAK then the interface
+ *      will also be called with actual times and the hardware is expected
+ *      to do the delay work itself. 0 and -1 are still used for on/off.
+ *
  *      Optional: Required for TCSBRK/BRKP/etc handling.
  *
  * void (*wait_until_sent)(struct tty_struct *tty, int timeout);
@@ -192,7 +196,7 @@ struct tty_operations {
         void (*stop)(struct tty_struct *tty);
         void (*start)(struct tty_struct *tty);
         void (*hangup)(struct tty_struct *tty);
-        void (*break_ctl)(struct tty_struct *tty, int state);
+        int (*break_ctl)(struct tty_struct *tty, int state);
         void (*flush_buffer)(struct tty_struct *tty);
         void (*set_ldisc)(struct tty_struct *tty);
         void (*wait_until_sent)(struct tty_struct *tty, int timeout);
@@ -285,12 +289,18 @@ extern struct tty_driver *tty_find_polling_driver(char *name, int *line);
  * TTY_DRIVER_DEVPTS_MEM -- don't use the standard arrays, instead
  *      use dynamic memory keyed through the devpts filesystem.  This
  *      is only applicable to the pty driver.
+ *
+ * TTY_DRIVER_HARDWARE_BREAK -- hardware handles break signals. Pass
+ *      the requested timeout to the caller instead of using a simple
+ *      on/off interface.
+ *
  */
 #define TTY_DRIVER_INSTALLED            0x0001
 #define TTY_DRIVER_RESET_TERMIOS        0x0002
 #define TTY_DRIVER_REAL_RAW             0x0004
 #define TTY_DRIVER_DYNAMIC_DEV          0x0008
 #define TTY_DRIVER_DEVPTS_MEM           0x0010
+#define TTY_DRIVER_HARDWARE_BREAK       0x0020
 
 /* tty driver types */
 #define TTY_DRIVER_TYPE_SYSTEM          0x0001