TTY: pty, switch to tty_alloc_driver

Switch to the new driver allocation interface, as this is one of the
special call-sites. Here, we need TTY_DRIVER_DYNAMIC_ALLOC to not
allocate tty_driver->ports, cdevs and potentially other structures
because we reserve too many lines in pty. Instead, it provides the
tty_port<->tty_struct link in tty->ops->install already.
Signed-off-by: NJiri Slaby <jslaby@suse.cz>
Acked-by: NAlan Cox <alan@linux.intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/pty.c

@@ -444,11 +444,17 @@ static void __init legacy_pty_init(void)
 	if (legacy_count <= 0)
 		return;
 
-	pty_driver = alloc_tty_driver(legacy_count);
+	pty_driver = tty_alloc_driver(legacy_count,
+			TTY_DRIVER_RESET_TERMIOS |
+			TTY_DRIVER_REAL_RAW |
+			TTY_DRIVER_DYNAMIC_ALLOC);
 	if (!pty_driver)
 		panic("Couldn't allocate pty driver");
 
-	pty_slave_driver = alloc_tty_driver(legacy_count);
+	pty_slave_driver = tty_alloc_driver(legacy_count,
+			TTY_DRIVER_RESET_TERMIOS |
+			TTY_DRIVER_REAL_RAW |
+			TTY_DRIVER_DYNAMIC_ALLOC);
 	if (!pty_slave_driver)
 		panic("Couldn't allocate pty slave driver");
 
@@ -465,7 +471,6 @@ static void __init legacy_pty_init(void)
 	pty_driver->init_termios.c_lflag = 0;
 	pty_driver->init_termios.c_ispeed = 38400;
 	pty_driver->init_termios.c_ospeed = 38400;
-	pty_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW;
 	pty_driver->other = pty_slave_driver;
 	tty_set_operations(pty_driver, &master_pty_ops_bsd);
 
@@ -479,8 +484,6 @@ static void __init legacy_pty_init(void)
 	pty_slave_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 	pty_slave_driver->init_termios.c_ispeed = 38400;
 	pty_slave_driver->init_termios.c_ospeed = 38400;
-	pty_slave_driver->flags = TTY_DRIVER_RESET_TERMIOS |
-					TTY_DRIVER_REAL_RAW;
 	pty_slave_driver->other = pty_driver;
 	tty_set_operations(pty_slave_driver, &slave_pty_ops_bsd);
 
@@ -673,10 +676,20 @@ static struct file_operations ptmx_fops;
 
 static void __init unix98_pty_init(void)
 {
-	ptm_driver = alloc_tty_driver(NR_UNIX98_PTY_MAX);
+	ptm_driver = tty_alloc_driver(NR_UNIX98_PTY_MAX,
+			TTY_DRIVER_RESET_TERMIOS |
+			TTY_DRIVER_REAL_RAW |
+			TTY_DRIVER_DYNAMIC_DEV |
+			TTY_DRIVER_DEVPTS_MEM |
+			TTY_DRIVER_DYNAMIC_ALLOC);
 	if (!ptm_driver)
 		panic("Couldn't allocate Unix98 ptm driver");
-	pts_driver = alloc_tty_driver(NR_UNIX98_PTY_MAX);
+	pts_driver = tty_alloc_driver(NR_UNIX98_PTY_MAX,
+			TTY_DRIVER_RESET_TERMIOS |
+			TTY_DRIVER_REAL_RAW |
+			TTY_DRIVER_DYNAMIC_DEV |
+			TTY_DRIVER_DEVPTS_MEM |
+			TTY_DRIVER_DYNAMIC_ALLOC);
 	if (!pts_driver)
 		panic("Couldn't allocate Unix98 pts driver");
 
@@ -693,8 +706,6 @@ static void __init unix98_pty_init(void)
 	ptm_driver->init_termios.c_lflag = 0;
 	ptm_driver->init_termios.c_ispeed = 38400;
 	ptm_driver->init_termios.c_ospeed = 38400;
-	ptm_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW |
-		TTY_DRIVER_DYNAMIC_DEV | TTY_DRIVER_DEVPTS_MEM;
 	ptm_driver->other = pts_driver;
 	tty_set_operations(ptm_driver, &ptm_unix98_ops);
 
@@ -708,8 +719,6 @@ static void __init unix98_pty_init(void)
 	pts_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
 	pts_driver->init_termios.c_ispeed = 38400;
 	pts_driver->init_termios.c_ospeed = 38400;
-	pts_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW |
-		TTY_DRIVER_DYNAMIC_DEV | TTY_DRIVER_DEVPTS_MEM;
 	pts_driver->other = ptm_driver;
 	tty_set_operations(pts_driver, &pty_unix98_ops);
 

include/linux/tty_driver.h

@@ -391,6 +391,9 @@ static inline struct tty_driver *tty_driver_kref_get(struct tty_driver *d)
  *	the requested timeout to the caller instead of using a simple
  *	on/off interface.
  *
+ * TTY_DRIVER_DYNAMIC_ALLOC -- do not allocate structures which are
+ *	needed per line for this driver as it would waste memory.
+ *	The driver will take care.
  */
 #define TTY_DRIVER_INSTALLED		0x0001
 #define TTY_DRIVER_RESET_TERMIOS	0x0002
@@ -398,6 +401,7 @@ static inline struct tty_driver *tty_driver_kref_get(struct tty_driver *d)
 #define TTY_DRIVER_DYNAMIC_DEV		0x0008
 #define TTY_DRIVER_DEVPTS_MEM		0x0010
 #define TTY_DRIVER_HARDWARE_BREAK	0x0020
+#define TTY_DRIVER_DYNAMIC_ALLOC	0x0040
 
 /* tty driver types */
 #define TTY_DRIVER_TYPE_SYSTEM		0x0001