1 files changed, 78 insertions, 0 deletions

diff --git a/drivers/char/pty.c b/drivers/char/pty.c
index ec09c1cd4fe9..328e8ac12306 100644
--- a/drivers/char/pty.c
+++ b/drivers/char/pty.c
@@ -23,6 +23,7 @@
 #include <linux/mm.h>
 #include <linux/init.h>
 #include <linux/sysctl.h>
+#include <linux/device.h>
 
 #include <asm/uaccess.h>
 #include <asm/system.h>
@@ -332,6 +333,8 @@ int pty_limit = NR_UNIX98_PTY_DEFAULT;
 static int pty_limit_min = 0;
 static int pty_limit_max = NR_UNIX98_PTY_MAX;
 
+static struct cdev ptmx_cdev;
+
 static struct ctl_table pty_table[] = {
         {
                 .ctl_name       = PTY_MAX,
@@ -408,6 +411,70 @@ static const struct tty_operations ptm_unix98_ops = {
         .shutdown = pty_shutdown
 };
 
+
+/**
+ *      ptmx_open               -       open a unix 98 pty master
+ *      @inode: inode of device file
+ *      @filp: file pointer to tty
+ *
+ *      Allocate a unix98 pty master device from the ptmx driver.
+ *
+ *      Locking: tty_mutex protects the init_dev work. tty->count should
+ *              protect the rest.
+ *              allocated_ptys_lock handles the list of free pty numbers
+ */
+
+static int __ptmx_open(struct inode *inode, struct file *filp)
+{
+        struct tty_struct *tty;
+        int retval;
+        int index;
+
+        nonseekable_open(inode, filp);
+
+        /* find a device that is not in use. */
+        index = devpts_new_index();
+        if (index < 0)
+                return index;
+
+        mutex_lock(&tty_mutex);
+        retval = tty_init_dev(ptm_driver, index, &tty, 1);
+        mutex_unlock(&tty_mutex);
+
+        if (retval)
+                goto out;
+
+        set_bit(TTY_PTY_LOCK, &tty->flags); /* LOCK THE SLAVE */
+        filp->private_data = tty;
+        file_move(filp, &tty->tty_files);
+
+        retval = devpts_pty_new(tty->link);
+        if (retval)
+                goto out1;
+
+        retval = ptm_driver->ops->open(tty, filp);
+        if (!retval)
+                return 0;
+out1:
+        tty_release_dev(filp);
+        return retval;
+out:
+        devpts_kill_index(index);
+        return retval;
+}
+
+static int ptmx_open(struct inode *inode, struct file *filp)
+{
+        int ret;
+
+        lock_kernel();
+        ret = __ptmx_open(inode, filp);
+        unlock_kernel();
+        return ret;
+}
+
+static struct file_operations ptmx_fops;
+
 static void __init unix98_pty_init(void)
 {
         ptm_driver = alloc_tty_driver(NR_UNIX98_PTY_MAX);
@@ -459,7 +526,18 @@ static void __init unix98_pty_init(void)
 
         pty_table[1].data = &ptm_driver->refcount;
         register_sysctl_table(pty_root_table);
+
+        /* Now create the /dev/ptmx special device */
+        tty_default_fops(&ptmx_fops);
+        ptmx_fops.open = ptmx_open;
+
+        cdev_init(&ptmx_cdev, &ptmx_fops);
+        if (cdev_add(&ptmx_cdev, MKDEV(TTYAUX_MAJOR, 2), 1) ||
+            register_chrdev_region(MKDEV(TTYAUX_MAJOR, 2), 1, "/dev/ptmx") < 0)
+                panic("Couldn't register /dev/ptmx driver\n");
+        device_create(tty_class, NULL, MKDEV(TTYAUX_MAJOR, 2), NULL, "ptmx");
 }
+
 #else
 static inline void unix98_pty_init(void) { }
 #endif