USB: serial: make minor allocation dynamic

This moves the allocation of minor device numbers from a static array to
be dynamic, using the idr interface.  This means that you could
potentially get "gaps" in a minor number range for a single USB serial
device with multiple ports, but all should still work properly.

We remove the 'minor' field from the usb_serial structure, as it no
longer makes any sense for it (use the field in the usb_serial_port
structure if you really want to know this number), and take the fact
that we were overloading a number in this field to determine if we had
initialized the minor numbers or not, and just use a flag variable
instead.

Note, we still have the limitation of 255 USB to serial devices in the
system, as that is all we are registering with the TTY layer at this
point in time.

Tested-by: Tobias Winter <tobias@linuxdingsda.de>
Reviewed-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 55 insertions, 68 deletions

diff --git a/drivers/usb/serial/usb-serial.c b/drivers/usb/serial/usb-serial.c
index a47fa715aaba..e2e131f85002 100644
--- a/drivers/usb/serial/usb-serial.c
+++ b/drivers/usb/serial/usb-serial.c
@@ -37,6 +37,7 @@
 #include <linux/usb.h>
 #include <linux/usb/serial.h>
 #include <linux/kfifo.h>
+#include <linux/idr.h>
 #include "pl2303.h"
 
 #define DRIVER_AUTHOR "Greg Kroah-Hartman <gregkh@linuxfoundation.org>"
@@ -49,82 +50,75 @@
    drivers depend on it.
 */
 
-static struct usb_serial *serial_table[SERIAL_TTY_MINORS];
+static DEFINE_IDR(serial_minors);
 static DEFINE_MUTEX(table_lock);
 static LIST_HEAD(usb_serial_driver_list);
 
 /*
- * Look up the serial structure.  If it is found and it hasn't been
- * disconnected, return with its disc_mutex held and its refcount
- * incremented.  Otherwise return NULL.
+ * Look up the serial port structure.  If it is found and it hasn't been
+ * disconnected, return with the parent usb_serial structure's disc_mutex held
+ * and its refcount incremented.  Otherwise return NULL.
  */
-struct usb_serial *usb_serial_get_by_index(unsigned index)
+struct usb_serial_port *usb_serial_port_get_by_minor(unsigned minor)
 {
 	struct usb_serial *serial;
+	struct usb_serial_port *port;
 
 	mutex_lock(&table_lock);
-	serial = serial_table[index];
-
-	if (serial) {
-		mutex_lock(&serial->disc_mutex);
-		if (serial->disconnected) {
-			mutex_unlock(&serial->disc_mutex);
-			serial = NULL;
-		} else {
-			kref_get(&serial->kref);
-		}
+	port = idr_find(&serial_minors, minor);
+	if (!port)
+		goto exit;
+
+	serial = port->serial;
+	mutex_lock(&serial->disc_mutex);
+	if (serial->disconnected) {
+		mutex_unlock(&serial->disc_mutex);
+		port = NULL;
+	} else {
+		kref_get(&serial->kref);
 	}
+exit:
 	mutex_unlock(&table_lock);
-	return serial;
+	return port;
 }
 
-static struct usb_serial *get_free_serial(struct usb_serial *serial,
-					int num_ports, unsigned int *minor)
+static int allocate_minors(struct usb_serial *serial, int num_ports)
 {
+	struct usb_serial_port *port;
 	unsigned int i, j;
-	int good_spot;
+	int minor;
 
 	dev_dbg(&serial->interface->dev, "%s %d\n", __func__, num_ports);
 
-	*minor = 0;
 	mutex_lock(&table_lock);
-	for (i = 0; i < SERIAL_TTY_MINORS; ++i) {
-		if (serial_table[i])
-			continue;
-
-		good_spot = 1;
-		for (j = 1; j <= num_ports-1; ++j)
-			if ((i+j >= SERIAL_TTY_MINORS) || (serial_table[i+j])) {
-				good_spot = 0;
-				i += j;
-				break;
-			}
-		if (good_spot == 0)
-			continue;
-
-		*minor = i;
-		j = 0;
-		dev_dbg(&serial->interface->dev, "%s - minor base = %d\n", __func__, *minor);
-		for (i = *minor; (i < (*minor + num_ports)) && (i < SERIAL_TTY_MINORS); ++i, ++j) {
-			serial_table[i] = serial;
-			serial->port[j]->minor = i;
-			serial->port[j]->port_number = i - *minor;
-		}
-		mutex_unlock(&table_lock);
-		return serial;
+	for (i = 0; i < num_ports; ++i) {
+		port = serial->port[i];
+		minor = idr_alloc(&serial_minors, port, 0, 0, GFP_KERNEL);
+		if (minor < 0)
+			goto error;
+		port->minor = minor;
+		port->port_number = i;
 	}
+	serial->minors_reserved = 1;
 	mutex_unlock(&table_lock);
-	return NULL;
+	return 0;
+error:
+	/* unwind the already allocated minors */
+	for (j = 0; j < i; ++j)
+		idr_remove(&serial_minors, serial->port[j]->minor);
+	mutex_unlock(&table_lock);
+	return minor;
 }
 
-static void return_serial(struct usb_serial *serial)
+static void release_minors(struct usb_serial *serial)
 {
 	int i;
 
 	mutex_lock(&table_lock);
 	for (i = 0; i < serial->num_ports; ++i)
-		serial_table[serial->minor + i] = NULL;
+		idr_remove(&serial_minors, serial->port[i]->minor);
 	mutex_unlock(&table_lock);
+	serial->minors_reserved = 0;
 }
 
 static void destroy_serial(struct kref *kref)
@@ -136,8 +130,8 @@ static void destroy_serial(struct kref *kref)
 	serial = to_usb_serial(kref);
 
 	/* return the minor range that this device had */
-	if (serial->minor != SERIAL_TTY_NO_MINOR)
-		return_serial(serial);
+	if (serial->minors_reserved)
+		release_minors(serial);
 
 	if (serial->attached && serial->type->release)
 		serial->type->release(serial);
@@ -186,13 +180,11 @@ static int serial_install(struct tty_driver *driver, struct tty_struct *tty)
 	struct usb_serial_port *port;
 	int retval = -ENODEV;
 
-	serial = usb_serial_get_by_index(idx);
-	if (!serial)
+	port = usb_serial_port_get_by_minor(idx);
+	if (!port)
 		return retval;
 
-	port = serial->port[idx - serial->minor];
-	if (!port)
-		goto error_no_port;
+	serial = port->serial;
 	if (!try_module_get(serial->type->driver.owner))
 		goto error_module_get;
 
@@ -219,7 +211,6 @@ static int serial_install(struct tty_driver *driver, struct tty_struct *tty)
  error_get_interface:
 	module_put(serial->type->driver.owner);
  error_module_get:
- error_no_port:
 	usb_serial_put(serial);
 	mutex_unlock(&serial->disc_mutex);
 	return retval;
@@ -453,14 +444,16 @@ static int serial_break(struct tty_struct *tty, int break_state)
 static int serial_proc_show(struct seq_file *m, void *v)
 {
 	struct usb_serial *serial;
+	struct usb_serial_port *port;
 	int i;
 	char tmp[40];
 
 	seq_puts(m, "usbserinfo:1.0 driver:2.0\n");
 	for (i = 0; i < SERIAL_TTY_MINORS; ++i) {
-		serial = usb_serial_get_by_index(i);
-		if (serial == NULL)
+		port = usb_serial_port_get_by_minor(i);
+		if (port == NULL)
 			continue;
+		serial = port->serial;
 
 		seq_printf(m, "%d:", i);
 		if (serial->type->driver.owner)
@@ -472,7 +465,7 @@ static int serial_proc_show(struct seq_file *m, void *v)
 			le16_to_cpu(serial->dev->descriptor.idVendor),
 			le16_to_cpu(serial->dev->descriptor.idProduct));
 		seq_printf(m, " num_ports:%d", serial->num_ports);
-		seq_printf(m, " port:%d", i - serial->minor + 1);
+		seq_printf(m, " port:%d", port->port_number);
 		usb_make_path(serial->dev, tmp, sizeof(tmp));
 		seq_printf(m, " path:%s", tmp);
 
@@ -614,7 +607,7 @@ static struct usb_serial *create_serial(struct usb_device *dev,
 	serial->interface = usb_get_intf(interface);
 	kref_init(&serial->kref);
 	mutex_init(&serial->disc_mutex);
-	serial->minor = SERIAL_TTY_NO_MINOR;
+	serial->minors_reserved = 0;
 
 	return serial;
 }
@@ -723,7 +716,6 @@ static int usb_serial_probe(struct usb_interface *interface,
 	struct usb_endpoint_descriptor *bulk_out_endpoint[MAX_NUM_PORTS];
 	struct usb_serial_driver *type = NULL;
 	int retval;
-	unsigned int minor;
 	int buffer_size;
 	int i;
 	int j;
@@ -1040,11 +1032,10 @@ static int usb_serial_probe(struct usb_interface *interface,
 	 */
 	serial->disconnected = 1;
 
-	if (get_free_serial(serial, num_ports, &minor) == NULL) {
-		dev_err(ddev, "No more free serial devices\n");
+	if (allocate_minors(serial, num_ports)) {
+		dev_err(ddev, "No more free serial minor numbers\n");
 		goto probe_error;
 	}
-	serial->minor = minor;
 
 	/* register all of the individual ports with the driver core */
 	for (i = 0; i < num_ports; ++i) {
@@ -1060,7 +1051,7 @@ static int usb_serial_probe(struct usb_interface *interface,
 
 	serial->disconnected = 0;
 
-	usb_serial_console_init(minor);
+	usb_serial_console_init(serial->port[0]->minor);
 exit:
 	module_put(type->driver.owner);
 	return 0;
@@ -1224,7 +1215,6 @@ static struct usb_driver usb_serial_driver = {
 
 static int __init usb_serial_init(void)
 {
-	int i;
 	int result;
 
 	usb_serial_tty_driver = alloc_tty_driver(SERIAL_TTY_MINORS);
@@ -1232,9 +1222,6 @@ static int __init usb_serial_init(void)
 		return -ENOMEM;
 
 	/* Initialize our global data */
-	for (i = 0; i < SERIAL_TTY_MINORS; ++i)
-		serial_table[i] = NULL;
-
 	result = bus_register(&usb_serial_bus_type);
 	if (result) {
 		pr_err("%s - registering bus driver failed\n", __func__);