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>

drivers/staging/serqt_usb2/serqt_usb2.c

@@ -906,7 +906,7 @@ static int qt_open(struct tty_struct *tty,
 			qt_submit_urb_from_open(serial, port);
 	}
 
-	dev_dbg(&port->dev, "serial number is %d\n", port->serial->minor);
+	dev_dbg(&port->dev, "minor number is %d\n", port->minor);
 	dev_dbg(&port->dev,
 		"Bulkin endpoint is %d\n", port->bulk_in_endpointAddress);
 	dev_dbg(&port->dev,
@@ -1002,7 +1002,7 @@ static void qt_close(struct usb_serial_port *port)
 	status = 0;
 
 	tty = tty_port_tty_get(&port->port);
-	index = tty->index - serial->minor;
+	index = port->port_number;
 
 	qt_port = qt_get_port_private(port);
 	port0 = qt_get_port_private(serial->port[0]);
@@ -1129,12 +1129,11 @@ static int qt_ioctl(struct tty_struct *tty,
 {
 	struct usb_serial_port *port = tty->driver_data;
 	struct quatech_port *qt_port = qt_get_port_private(port);
-	struct usb_serial *serial = get_usb_serial(port, __func__);
 	unsigned int index;
 
 	dev_dbg(&port->dev, "%s cmd 0x%04x\n", __func__, cmd);
 
-	index = tty->index - serial->minor;
+	index = port->port_number;
 
 	if (cmd == TIOCMIWAIT) {
 		while (qt_port != NULL) {
@@ -1180,7 +1179,7 @@ static void qt_set_termios(struct tty_struct *tty,
 	int baud, divisor, remainder;
 	int status;
 
-	index = tty->index - port->serial->minor;
+	index = port->port_number;
 
 	switch (cflag & CSIZE) {
 	case CS5:
@@ -1296,7 +1295,7 @@ static void qt_break(struct tty_struct *tty, int break_state)
 	u16 index, onoff;
 	unsigned int result;
 
-	index = tty->index - serial->minor;
+	index = port->port_number;
 
 	qt_port = qt_get_port_private(port);
 
@@ -1325,7 +1324,7 @@ static inline int qt_real_tiocmget(struct tty_struct *tty,
 	int status;
 	unsigned int index;
 
-	index = tty->index - serial->minor;
+	index = port->port_number;
 	status =
 	    BoxGetRegister(port->serial, index, MODEM_CONTROL_REGISTER, &mcr);
 	if (status >= 0) {
@@ -1364,7 +1363,7 @@ static inline int qt_real_tiocmset(struct tty_struct *tty,
 	int status;
 	unsigned int index;
 
-	index = tty->index - serial->minor;
+	index = port->port_number;
 	status =
 	    BoxGetRegister(port->serial, index, MODEM_CONTROL_REGISTER, &mcr);
 	if (status < 0)

drivers/usb/serial/ark3116.c

@@ -413,7 +413,7 @@ static int ark3116_ioctl(struct tty_struct *tty,
 		/* XXX: Some of these values are probably wrong. */
 		memset(&serstruct, 0, sizeof(serstruct));
 		serstruct.type = PORT_16654;
-		serstruct.line = port->serial->minor;
+		serstruct.line = port->minor;
 		serstruct.port = port->port_number;
 		serstruct.custom_divisor = 0;
 		serstruct.baud_base = 460800;

drivers/usb/serial/console.c

@@ -108,18 +108,18 @@ static int usb_console_setup(struct console *co, char *options)
 	 * no need to check the index here: if the index is wrong, console
 	 * code won't call us
 	 */
-	serial = usb_serial_get_by_index(co->index);
-	if (serial == NULL) {
+	port = usb_serial_port_get_by_minor(co->index);
+	if (port == NULL) {
 		/* no device is connected yet, sorry :( */
 		pr_err("No USB device connected to ttyUSB%i\n", co->index);
 		return -ENODEV;
 	}
+	serial = port->serial;
 
 	retval = usb_autopm_get_interface(serial->interface);
 	if (retval)
 		goto error_get_interface;
 
-	port = serial->port[co->index - serial->minor];
 	tty_port_tty_set(&port->port, NULL);
 
 	info->port = port;

drivers/usb/serial/f81232.c

@@ -294,7 +294,7 @@ static int f81232_ioctl(struct tty_struct *tty,
 	case TIOCGSERIAL:
 		memset(&ser, 0, sizeof ser);
 		ser.type = PORT_16654;
-		ser.line = port->serial->minor;
+		ser.line = port->minor;
 		ser.port = port->port_number;
 		ser.baud_base = 460800;
 

drivers/usb/serial/io_edgeport.c

@@ -1569,7 +1569,7 @@ static int get_serial_info(struct edgeport_port *edge_port,
 	memset(&tmp, 0, sizeof(tmp));
 
 	tmp.type		= PORT_16550A;
-	tmp.line		= edge_port->port->serial->minor;
+	tmp.line		= edge_port->port->minor;
 	tmp.port		= edge_port->port->port_number;
 	tmp.irq			= 0;
 	tmp.flags		= ASYNC_SKIP_TEST | ASYNC_AUTO_IRQ;

drivers/usb/serial/io_ti.c

@@ -2363,7 +2363,7 @@ static int get_serial_info(struct edgeport_port *edge_port,
 	memset(&tmp, 0, sizeof(tmp));
 
 	tmp.type		= PORT_16550A;
-	tmp.line		= edge_port->port->serial->minor;
+	tmp.line		= edge_port->port->minor;
 	tmp.port		= edge_port->port->port_number;
 	tmp.irq			= 0;
 	tmp.flags		= ASYNC_SKIP_TEST | ASYNC_AUTO_IRQ;

drivers/usb/serial/mos7720.c

@@ -1854,7 +1854,7 @@ static int get_serial_info(struct moschip_port *mos7720_port,
 	memset(&tmp, 0, sizeof(tmp));
 
 	tmp.type		= PORT_16550A;
-	tmp.line		= mos7720_port->port->serial->minor;
+	tmp.line		= mos7720_port->port->minor;
 	tmp.port		= mos7720_port->port->port_number;
 	tmp.irq			= 0;
 	tmp.flags		= ASYNC_SKIP_TEST | ASYNC_AUTO_IRQ;

drivers/usb/serial/mos7840.c

@@ -1057,7 +1057,7 @@ static int mos7840_open(struct tty_struct *tty, struct usb_serial_port *port)
 	 * structures were not set up at that time.)   */
 
 	dev_dbg(&port->dev, "port number is %d\n", port->port_number);
-	dev_dbg(&port->dev, "minor number is %d\n", port->serial->minor);
+	dev_dbg(&port->dev, "minor number is %d\n", port->minor);
 	dev_dbg(&port->dev, "Bulkin endpoint is %d\n", port->bulk_in_endpointAddress);
 	dev_dbg(&port->dev, "BulkOut endpoint is %d\n", port->bulk_out_endpointAddress);
 	dev_dbg(&port->dev, "Interrupt endpoint is %d\n", port->interrupt_in_endpointAddress);
@@ -2068,7 +2068,7 @@ static int mos7840_get_serial_info(struct moschip_port *mos7840_port,
 	memset(&tmp, 0, sizeof(tmp));
 
 	tmp.type = PORT_16550A;
-	tmp.line = mos7840_port->port->serial->minor;
+	tmp.line = mos7840_port->port->minor;
 	tmp.port = mos7840_port->port->port_number;
 	tmp.irq = 0;
 	tmp.flags = ASYNC_SKIP_TEST | ASYNC_AUTO_IRQ;
@@ -2246,9 +2246,8 @@ static int mos7840_port_probe(struct usb_serial_port *port)
 	 * usb-serial.c:get_free_serial() and cannot therefore be used
 	 * to index device instances */
 	mos7840_port->port_num = pnum + 1;
-	dev_dbg(&port->dev, "port->serial->minor = %d\n", port->serial->minor);
+	dev_dbg(&port->dev, "port->minor = %d\n", port->minor);
 	dev_dbg(&port->dev, "mos7840_port->port_num = %d\n", mos7840_port->port_num);
-	dev_dbg(&port->dev, "serial->minor = %d\n", serial->minor);
 
 	if (mos7840_port->port_num == 1) {
 		mos7840_port->SpRegOffset = 0x0;

drivers/usb/serial/opticon.c

@@ -348,7 +348,7 @@ static int get_serial_info(struct usb_serial_port *port,
 
 	/* fake emulate a 16550 uart to make userspace code happy */
 	tmp.type		= PORT_16550A;
-	tmp.line		= port->serial->minor;
+	tmp.line		= port->minor;
 	tmp.port		= 0;
 	tmp.irq			= 0;
 	tmp.flags		= ASYNC_SKIP_TEST | ASYNC_AUTO_IRQ;

drivers/usb/serial/pl2303.c

@@ -639,7 +639,7 @@ static int pl2303_ioctl(struct tty_struct *tty,
 	case TIOCGSERIAL:
 		memset(&ser, 0, sizeof ser);
 		ser.type = PORT_16654;
-		ser.line = port->serial->minor;
+		ser.line = port->minor;
 		ser.port = port->port_number;
 		ser.baud_base = 460800;
 

drivers/usb/serial/quatech2.c

@@ -465,7 +465,7 @@ static int get_serial_info(struct usb_serial_port *port,
 		return -EFAULT;
 
 	memset(&tmp, 0, sizeof(tmp));
-	tmp.line		= port->serial->minor;
+	tmp.line		= port->minor;
 	tmp.port		= 0;
 	tmp.irq			= 0;
 	tmp.flags		= ASYNC_SKIP_TEST | ASYNC_AUTO_IRQ;

drivers/usb/serial/ssu100.c

@@ -323,7 +323,7 @@ static int get_serial_info(struct usb_serial_port *port,
 		return -EFAULT;
 
 	memset(&tmp, 0, sizeof(tmp));
-	tmp.line		= port->serial->minor;
+	tmp.line		= port->minor;
 	tmp.port		= 0;
 	tmp.irq			= 0;
 	tmp.flags		= ASYNC_SKIP_TEST | ASYNC_AUTO_IRQ;

drivers/usb/serial/ti_usb_3410_5052.c

@@ -1308,7 +1308,7 @@ static int ti_get_serial_info(struct ti_port *tport,
 	memset(&ret_serial, 0, sizeof(ret_serial));
 
 	ret_serial.type = PORT_16550A;
-	ret_serial.line = port->serial->minor;
+	ret_serial.line = port->minor;
 	ret_serial.port = port->port_number;
 	ret_serial.flags = tport->tp_flags;
 	ret_serial.xmit_fifo_size = TI_WRITE_BUF_SIZE;

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__);

drivers/usb/serial/usb_wwan.c

@@ -124,7 +124,7 @@ static int get_serial_info(struct usb_serial_port *port,
 		return -EFAULT;
 
 	memset(&tmp, 0, sizeof(tmp));
-	tmp.line            = port->serial->minor;
+	tmp.line            = port->minor;
 	tmp.port            = port->port_number;
 	tmp.baud_base       = tty_get_baud_rate(port->port.tty);
 	tmp.close_delay	    = port->port.close_delay / 10;

drivers/usb/serial/whiteheat.c

@@ -461,7 +461,7 @@ static int whiteheat_ioctl(struct tty_struct *tty,
 	case TIOCGSERIAL:
 		memset(&serstruct, 0, sizeof(serstruct));
 		serstruct.type = PORT_16654;
-		serstruct.line = port->serial->minor;
+		serstruct.line = port->minor;
 		serstruct.port = port->port_number;
 		serstruct.flags = ASYNC_SKIP_TEST | ASYNC_AUTO_IRQ;
 		serstruct.xmit_fifo_size = kfifo_size(&port->write_fifo);

include/linux/usb/serial.h

@@ -21,7 +21,6 @@
 
 #define SERIAL_TTY_MAJOR	188	/* Nice legal number now */
 #define SERIAL_TTY_MINORS	254	/* loads of devices :) */
-#define SERIAL_TTY_NO_MINOR	255	/* No minor was assigned */
 
 /* The maximum number of ports one device can grab at once */
 #define MAX_NUM_PORTS		8
@@ -142,7 +141,6 @@ static inline void usb_set_serial_port_data(struct usb_serial_port *port,
  * @dev: pointer to the struct usb_device for this device
  * @type: pointer to the struct usb_serial_driver for this device
  * @interface: pointer to the struct usb_interface for this device
- * @minor: the starting minor number for this device
  * @num_ports: the number of ports this device has
  * @num_interrupt_in: number of interrupt in endpoints we have
  * @num_interrupt_out: number of interrupt out endpoints we have
@@ -161,7 +159,7 @@ struct usb_serial {
 	unsigned char			disconnected:1;
 	unsigned char			suspending:1;
 	unsigned char			attached:1;
-	unsigned char			minor;
+	unsigned char			minors_reserved:1;
 	unsigned char			num_ports;
 	unsigned char			num_port_pointers;
 	char				num_interrupt_in;
@@ -321,7 +319,7 @@ static inline void usb_serial_console_disconnect(struct usb_serial *serial) {}
 #endif
 
 /* Functions needed by other parts of the usbserial core */
-extern struct usb_serial *usb_serial_get_by_index(unsigned int minor);
+extern struct usb_serial_port *usb_serial_port_get_by_minor(unsigned int minor);
 extern void usb_serial_put(struct usb_serial *serial);
 extern int usb_serial_generic_open(struct tty_struct *tty,
 	struct usb_serial_port *port);