tty: The big operations rework
- Operations are now a shared const function block as with most other Linux
objects
- Introduce wrappers for some optional functions to get consistent behaviour
- Wrap put_char which used to be patched by the tty layer
- Document which functions are needed/optional
- Make put_char report success/fail
- Cache the driver->ops pointer in the tty as tty->ops
- Remove various surplus lock calls we no longer need
- Remove proc_write method as noted by Alexey Dobriyan
- Introduce some missing sanity checks where certain driver/ldisc
combinations would oops as they didn't check needed methods were present
[akpm@linux-foundation.org: fix fs/compat_ioctl.c build]
[akpm@linux-foundation.org: fix isicom]
[akpm@linux-foundation.org: fix arch/ia64/hp/sim/simserial.c build]
[akpm@linux-foundation.org: fix kgdb]
Signed-off-by: Alan Cox <alan@redhat.com>
Acked-by: Greg Kroah-Hartman <gregkh@suse.de>
Cc: Jason Wessel <jason.wessel@windriver.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/tty_driver.h b/include/linux/tty_driver.h
index 21f69ac..f80d73b 100644
--- a/include/linux/tty_driver.h
+++ b/include/linux/tty_driver.h
@@ -12,11 +12,15 @@
* This routine is called when a particular tty device is opened.
* This routine is mandatory; if this routine is not filled in,
* the attempted open will fail with ENODEV.
+ *
+ * Required method.
*
* void (*close)(struct tty_struct * tty, struct file * filp);
*
* This routine is called when a particular tty device is closed.
*
+ * Required method.
+ *
* int (*write)(struct tty_struct * tty,
* const unsigned char *buf, int count);
*
@@ -26,7 +30,9 @@
* number of characters actually accepted for writing. This
* routine is mandatory.
*
- * void (*put_char)(struct tty_struct *tty, unsigned char ch);
+ * Optional: Required for writable devices.
+ *
+ * int (*put_char)(struct tty_struct *tty, unsigned char ch);
*
* This routine is called by the kernel to write a single
* character to the tty device. If the kernel uses this routine,
@@ -34,10 +40,18 @@
* done stuffing characters into the driver. If there is no room
* in the queue, the character is ignored.
*
+ * Optional: Kernel will use the write method if not provided.
+ *
+ * Note: Do not call this function directly, call tty_put_char
+ *
* void (*flush_chars)(struct tty_struct *tty);
*
* This routine is called by the kernel after it has written a
* series of characters to the tty device using put_char().
+ *
+ * Optional:
+ *
+ * Note: Do not call this function directly, call tty_driver_flush_chars
*
* int (*write_room)(struct tty_struct *tty);
*
@@ -45,6 +59,10 @@
* will accept for queuing to be written. This number is subject
* to change as output buffers get emptied, or if the output flow
* control is acted.
+ *
+ * Required if write method is provided else not needed.
+ *
+ * Note: Do not call this function directly, call tty_write_room
*
* int (*ioctl)(struct tty_struct *tty, struct file * file,
* unsigned int cmd, unsigned long arg);
@@ -53,22 +71,29 @@
* device-specific ioctl's. If the ioctl number passed in cmd
* is not recognized by the driver, it should return ENOIOCTLCMD.
*
+ * Optional
+ *
* long (*compat_ioctl)(struct tty_struct *tty, struct file * file,
* unsigned int cmd, unsigned long arg);
*
* implement ioctl processing for 32 bit process on 64 bit system
+ *
+ * Optional
*
* void (*set_termios)(struct tty_struct *tty, struct ktermios * old);
*
* This routine allows the tty driver to be notified when
- * device's termios settings have changed. Note that a
- * well-designed tty driver should be prepared to accept the case
- * where old == NULL, and try to do something rational.
+ * device's termios settings have changed.
+ *
+ * Optional: Called under the termios lock
+ *
*
* void (*set_ldisc)(struct tty_struct *tty);
*
* This routine allows the tty driver to be notified when the
* device's termios settings have changed.
+ *
+ * Optional: Called under BKL (currently)
*
* void (*throttle)(struct tty_struct * tty);
*
@@ -86,17 +111,27 @@
*
* This routine notifies the tty driver that it should stop
* outputting characters to the tty device.
+ *
+ * Optional:
+ *
+ * Note: Call stop_tty not this method.
*
* void (*start)(struct tty_struct *tty);
*
* This routine notifies the tty driver that it resume sending
* characters to the tty device.
+ *
+ * Optional:
+ *
+ * Note: Call start_tty not this method.
*
* void (*hangup)(struct tty_struct *tty);
*
* This routine notifies the tty driver that it should hangup the
* tty device.
*
+ * Required:
+ *
* void (*break_ctl)(struct tty_stuct *tty, int state);
*
* This optional routine requests the tty driver to turn on or
@@ -106,18 +141,26 @@
*
* If this routine is implemented, the high-level tty driver will
* handle the following ioctls: TCSBRK, TCSBRKP, TIOCSBRK,
- * TIOCCBRK. Otherwise, these ioctls will be passed down to the
- * driver to handle.
+ * TIOCCBRK.
+ *
+ * Optional: Required for TCSBRK/BRKP/etc handling.
*
* void (*wait_until_sent)(struct tty_struct *tty, int timeout);
*
* This routine waits until the device has written out all of the
* characters in its transmitter FIFO.
*
+ * Optional: If not provided the device is assumed to have no FIFO
+ *
+ * Note: Usually correct to call tty_wait_until_sent
+ *
* void (*send_xchar)(struct tty_struct *tty, char ch);
*
* This routine is used to send a high-priority XON/XOFF
* character to the device.
+ *
+ * Optional: If not provided then the write method is called under
+ * the atomic write lock to keep it serialized with the ldisc.
*/
#include <linux/fs.h>
@@ -132,7 +175,7 @@
void (*close)(struct tty_struct * tty, struct file * filp);
int (*write)(struct tty_struct * tty,
const unsigned char *buf, int count);
- void (*put_char)(struct tty_struct *tty, unsigned char ch);
+ int (*put_char)(struct tty_struct *tty, unsigned char ch);
void (*flush_chars)(struct tty_struct *tty);
int (*write_room)(struct tty_struct *tty);
int (*chars_in_buffer)(struct tty_struct *tty);
@@ -153,8 +196,6 @@
void (*send_xchar)(struct tty_struct *tty, char ch);
int (*read_proc)(char *page, char **start, off_t off,
int count, int *eof, void *data);
- int (*write_proc)(struct file *file, const char __user *buffer,
- unsigned long count, void *data);
int (*tiocmget)(struct tty_struct *tty, struct file *file);
int (*tiocmset)(struct tty_struct *tty, struct file *file,
unsigned int set, unsigned int clear);
@@ -190,48 +231,13 @@
struct tty_struct **ttys;
struct ktermios **termios;
struct ktermios **termios_locked;
- void *driver_state; /* only used for the PTY driver */
-
- /*
- * Interface routines from the upper tty layer to the tty
- * driver. Will be replaced with struct tty_operations.
- */
- int (*open)(struct tty_struct * tty, struct file * filp);
- void (*close)(struct tty_struct * tty, struct file * filp);
- int (*write)(struct tty_struct * tty,
- const unsigned char *buf, int count);
- void (*put_char)(struct tty_struct *tty, unsigned char ch);
- void (*flush_chars)(struct tty_struct *tty);
- int (*write_room)(struct tty_struct *tty);
- int (*chars_in_buffer)(struct tty_struct *tty);
- int (*ioctl)(struct tty_struct *tty, struct file * file,
- unsigned int cmd, unsigned long arg);
- long (*compat_ioctl)(struct tty_struct *tty, struct file * file,
- unsigned int cmd, unsigned long arg);
- void (*set_termios)(struct tty_struct *tty, struct ktermios * old);
- void (*throttle)(struct tty_struct * tty);
- void (*unthrottle)(struct tty_struct * tty);
- 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);
- void (*flush_buffer)(struct tty_struct *tty);
- void (*set_ldisc)(struct tty_struct *tty);
- void (*wait_until_sent)(struct tty_struct *tty, int timeout);
- void (*send_xchar)(struct tty_struct *tty, char ch);
- int (*read_proc)(char *page, char **start, off_t off,
- int count, int *eof, void *data);
- int (*write_proc)(struct file *file, const char __user *buffer,
- unsigned long count, void *data);
- int (*tiocmget)(struct tty_struct *tty, struct file *file);
- int (*tiocmset)(struct tty_struct *tty, struct file *file,
- unsigned int set, unsigned int clear);
-#ifdef CONFIG_CONSOLE_POLL
- int (*poll_init)(struct tty_driver *driver, int line, char *options);
- int (*poll_get_char)(struct tty_driver *driver, int line);
- void (*poll_put_char)(struct tty_driver *driver, int line, char ch);
-#endif
+ void *driver_state;
+ /*
+ * Driver methods
+ */
+
+ const struct tty_operations *ops;
struct list_head tty_drivers;
};