um: switch line.c tty drivers to dynamic device creation

Current code doesn't update the symlinks in /sys/dev/char when we add/remove
tty lines.  Fixing that allows to stop messing with ->valid before the driver
registration, which is a Good Thing(tm) - we shouldn't have it set before we
really have the things set up and ready for line_open().

We need tty_driver available to call tty_{un,}register_device(), so we just
stash a reference to it into struct line_driver.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Richard Weinberger <richard@nod.at>

arch/um/drivers/line.c

@@ -485,6 +485,7 @@ static int setup_one_line(struct line *lines, int n, char *init,
 			  const struct chan_opts *opts, char **error_out)
 {
 	struct line *line = &lines[n];
+	struct tty_driver *driver = line->driver->driver;
 	int err = -EINVAL;
 
 	mutex_lock(&line->count_lock);
@@ -498,6 +499,7 @@ static int setup_one_line(struct line *lines, int n, char *init,
 		if (line->valid) {
 			line->valid = 0;
 			kfree(line->init_str);
+			tty_unregister_device(driver, n);
 			parse_chan_pair(NULL, line, n, opts, error_out);
 			err = 0;
 		}
@@ -507,9 +509,19 @@ static int setup_one_line(struct line *lines, int n, char *init,
 			*error_out = "Failed to allocate memory";
 			return -ENOMEM;
 		}
+		if (line->valid)
+			tty_unregister_device(driver, n);
 		line->init_str = new;
 		line->valid = 1;
 		err = parse_chan_pair(new, line, n, opts, error_out);
+		if (!err) {
+			struct device *d = tty_register_device(driver, n, NULL);
+			if (IS_ERR(d)) {
+				*error_out = "Failed to register device";
+				err = PTR_ERR(d);
+				parse_chan_pair(NULL, line, n, opts, error_out);
+			}
+		}
 		if (err) {
 			line->init_str = NULL;
 			line->valid = 0;
@@ -640,15 +652,15 @@ int line_remove(struct line *lines, unsigned int num, int n, char **error_out)
 	return setup_one_line(lines, n, "none", NULL, error_out);
 }
 
-struct tty_driver *register_lines(struct line_driver *line_driver,
+int register_lines(struct line_driver *line_driver,
 		   const struct tty_operations *ops,
 		   struct line *lines, int nlines)
 {
-	int i;
 	struct tty_driver *driver = alloc_tty_driver(nlines);
+	int err;
 
 	if (!driver)
-		return NULL;
+		return -ENOMEM;
 
 	driver->driver_name = line_driver->name;
 	driver->name = line_driver->device_name;
@@ -656,24 +668,21 @@ struct tty_driver *register_lines(struct line_driver *line_driver,
 	driver->minor_start = line_driver->minor_start;
 	driver->type = line_driver->type;
 	driver->subtype = line_driver->subtype;
-	driver->flags = TTY_DRIVER_REAL_RAW;
+	driver->flags = TTY_DRIVER_REAL_RAW | TTY_DRIVER_DYNAMIC_DEV;
 	driver->init_termios = tty_std_termios;
 	tty_set_operations(driver, ops);
 
-	if (tty_register_driver(driver)) {
+	err = tty_register_driver(driver);
+	if (err) {
 		printk(KERN_ERR "register_lines : can't register %s driver\n",
 		       line_driver->name);
 		put_tty_driver(driver);
-		return NULL;
-	}
-
-	for(i = 0; i < nlines; i++) {
-		if (!lines[i].valid)
-			tty_unregister_device(driver, i);
+		return err;
 	}
 
+	line_driver->driver = driver;
 	mconsole_register_dev(&line_driver->mc);
-	return driver;
+	return 0;
 }
 
 static DEFINE_SPINLOCK(winch_handler_lock);

arch/um/drivers/line.h

@@ -15,7 +15,7 @@
 #include "chan_user.h"
 #include "mconsole_kern.h"
 
-/* There's only one modifiable field in this - .mc.list */
+/* There's only two modifiable fields in this - .mc.list and .driver */
 struct line_driver {
 	const char *name;
 	const char *device_name;
@@ -28,6 +28,7 @@ struct line_driver {
 	const int write_irq;
 	const char *write_irq_name;
 	struct mc_device mc;
+	struct tty_driver *driver;
 };
 
 struct line {
@@ -78,7 +79,7 @@ extern char *add_xterm_umid(char *base);
 extern int line_setup_irq(int fd, int input, int output, struct line *line,
 			  void *data);
 extern void line_close_chan(struct line *line);
-extern struct tty_driver *register_lines(struct line_driver *line_driver,
+extern int register_lines(struct line_driver *line_driver,
 			  const struct tty_operations *driver,
 			  struct line *lines, int nlines);
 extern void lines_init(struct line *lines, int nlines, struct chan_opts *opts);

arch/um/drivers/ssl.c

@@ -20,12 +20,6 @@
 
 static const int ssl_version = 1;
 
-/* Referenced only by tty_driver below - presumably it's locked correctly
- * by the tty driver.
- */
-
-static struct tty_driver *ssl_driver;
-
 #define NR_PORTS 64
 
 static void ssl_announce(char *dev_name, int dev)
@@ -164,7 +158,7 @@ static void ssl_console_write(struct console *c, const char *string,
 static struct tty_driver *ssl_console_device(struct console *c, int *index)
 {
 	*index = c->index;
-	return ssl_driver;
+	return driver.driver;
 }
 
 static int ssl_console_setup(struct console *co, char *options)
@@ -187,6 +181,7 @@ static struct console ssl_cons = {
 static int ssl_init(void)
 {
 	char *new_title;
+	int err;
 	int i;
 
 	printk(KERN_INFO "Initializing software serial port version %d\n",
@@ -196,16 +191,16 @@ static int ssl_init(void)
 		char *s = conf[i];
 		if (!s)
 			s = def_conf;
-		if (s && strcmp(s, "none") != 0) {
+		if (s && strcmp(s, "none") != 0)
 			serial_lines[i].init_str = s;
-			serial_lines[i].valid = 1;
-		}
 		spin_lock_init(&serial_lines[i].lock);
 		mutex_init(&serial_lines[i].count_lock);
 		serial_lines[i].driver = &driver;
 	}
-	ssl_driver = register_lines(&driver, &ssl_ops, serial_lines,
+	err = register_lines(&driver, &ssl_ops, serial_lines,
 				    ARRAY_SIZE(serial_lines));
+	if (err)
+		return err;
 
 	new_title = add_xterm_umid(opts.xterm_title);
 	if (new_title != NULL)

arch/um/drivers/stdio_console.c

@@ -27,12 +27,6 @@
 
 #define MAX_TTYS (16)
 
-/* Referenced only by tty_driver below - presumably it's locked correctly
- * by the tty driver.
- */
-
-static struct tty_driver *console_driver;
-
 static void stdio_announce(char *dev_name, int dev)
 {
 	printk(KERN_INFO "Virtual console %d assigned device '%s'\n", dev,
@@ -137,7 +131,7 @@ static void uml_console_write(struct console *console, const char *string,
 static struct tty_driver *uml_console_device(struct console *c, int *index)
 {
 	*index = c->index;
-	return console_driver;
+	return driver.driver;
 }
 
 static int uml_console_setup(struct console *co, char *options)
@@ -160,6 +154,7 @@ static struct console stdiocons = {
 static int stdio_init(void)
 {
 	char *new_title;
+	int err;
 	int i;
 
 	for (i = 0; i < MAX_TTYS; i++) {
@@ -168,18 +163,16 @@ static int stdio_init(void)
 			s = def_conf;
 		if (!s)
 			s = i ? CONFIG_CON_CHAN : CONFIG_CON_ZERO_CHAN;
-		if (s && strcmp(s, "none") != 0) {
+		if (s && strcmp(s, "none") != 0)
 			vts[i].init_str = s;
-			vts[i].valid = 1;
-		}
 		spin_lock_init(&vts[i].lock);
 		mutex_init(&vts[i].count_lock);
 		vts[i].driver = &driver;
 	}
-	console_driver = register_lines(&driver, &console_ops, vts,
+	err = register_lines(&driver, &console_ops, vts,
 					ARRAY_SIZE(vts));
-	if (console_driver == NULL)
-		return -1;
+	if (err)
+		return err;
 	printk(KERN_INFO "Initialized stdio console driver\n");
 
 	new_title = add_xterm_umid(opts.xterm_title);