PTY: add tty_port

This has *no* function in the PTY driver yet. However as the tty
buffers will move to the tty_port structure, we will need tty_port for
all TTYs in the system, PTY inclusive.

For PTYs this is ensured by allocating 2 tty_port's in pty_install,
i.e. where the tty->link is allocated. Both tty_port's are properly
assigned to each end of the tty.

Freeing is done at the same place where tty is freed, i.e. in
tty->ops->cleanup.

This means BTW that tty_port does not outlive TTY in PTY. This might
be a subject to change in the future if we see some problems.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 21 insertions, 4 deletions

diff --git a/drivers/tty/pty.c b/drivers/tty/pty.c
index 881888f0a445..b50fc1c01415 100644
--- a/drivers/tty/pty.c
+++ b/drivers/tty/pty.c
@@ -286,12 +286,15 @@ static int pty_common_install(struct tty_driver *driver, struct tty_struct *tty,
                 bool legacy)
 {
         struct tty_struct *o_tty;
+        struct tty_port *ports[2];
         int idx = tty->index;
         int retval = -ENOMEM;
 
         o_tty = alloc_tty_struct();
-        if (!o_tty)
-                goto err;
+        ports[0] = kmalloc(sizeof **ports, GFP_KERNEL);
+        ports[1] = kmalloc(sizeof **ports, GFP_KERNEL);
+        if (!o_tty || !ports[0] || !ports[1])
+                goto err_free_tty;
         if (!try_module_get(driver->other->owner)) {
                 /* This cannot in fact currently happen */
                 goto err_free_tty;
@@ -335,6 +338,10 @@ static int pty_common_install(struct tty_driver *driver, struct tty_struct *tty,
         /* Establish the links in both directions */
         tty->link   = o_tty;
         o_tty->link = tty;
+        tty_port_init(ports[0]);
+        tty_port_init(ports[1]);
+        o_tty->port = ports[0];
+        tty->port = ports[1];
 
         tty_driver_kref_get(driver);
         tty->count++;
@@ -348,11 +355,17 @@ err_deinit_tty:
         deinitialize_tty_struct(o_tty);
         module_put(o_tty->driver->owner);
 err_free_tty:
+        kfree(ports[0]);
+        kfree(ports[1]);
         free_tty_struct(o_tty);
-err:
         return retval;
 }
 
+static void pty_cleanup(struct tty_struct *tty)
+{
+        kfree(tty->port);
+}
+
 /* Traditional BSD devices */
 #ifdef CONFIG_LEGACY_PTYS
 
@@ -391,6 +404,7 @@ static const struct tty_operations master_pty_ops_bsd = {
         .unthrottle = pty_unthrottle,
         .set_termios = pty_set_termios,
         .ioctl = pty_bsd_ioctl,
+        .cleanup = pty_cleanup,
         .resize = pty_resize
 };
 
@@ -404,6 +418,7 @@ static const struct tty_operations slave_pty_ops_bsd = {
         .chars_in_buffer = pty_chars_in_buffer,
         .unthrottle = pty_unthrottle,
         .set_termios = pty_set_termios,
+        .cleanup = pty_cleanup,
         .resize = pty_resize
 };
 
@@ -555,6 +570,7 @@ static const struct tty_operations ptm_unix98_ops = {
         .set_termios = pty_set_termios,
         .ioctl = pty_unix98_ioctl,
         .shutdown = pty_unix98_shutdown,
+        .cleanup = pty_cleanup,
         .resize = pty_resize
 };
 
@@ -570,7 +586,8 @@ static const struct tty_operations pty_unix98_ops = {
         .chars_in_buffer = pty_chars_in_buffer,
         .unthrottle = pty_unthrottle,
         .set_termios = pty_set_termios,
-        .shutdown = pty_unix98_shutdown
+        .shutdown = pty_unix98_shutdown,
+        .cleanup = pty_cleanup,
 };
 
 /**