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Date: Mon, 3 Jun 2013 19:49:59 -0700
From: Greg KH <greg@...ah.com>
To: Tobias Winter <tobias@...uxdingsda.de>,
Bjørn Mork <bjorn@...k.no>,
Rob Landley <rob@...dley.net>
Cc: linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC] raise the maximum number of usb-serial devices to 512
On Mon, May 27, 2013 at 02:28:51PM +0200, Bjørn Mork wrote:
> But, IMHO, a nicer approach would be to make the allocation completely
> dynamic, using e.g. the idr subsystem. Static tables are always feel
> like straight jackets to me, no matter how big they are :)
You are right, I didn't change the code to use idr (it predates idr by
about a decade or so), because I thought we needed the "rage" logic that
the usb-serial minor reservation does.
But I'm not so sure anymore, so here's a patch to change to use the idr
code, and should remove all minor number limitations (well 65k is the
limit the tty core should be setting I think.)
Tobias, can you test this patch out? Note, I only compiled it, did not
get the chance to actually run it, so it might not work at all.
thanks,
greg k-h
Subject: [PATCH] usb: serial: remove minor number limitation of 255
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
drivers/usb/serial/usb-serial.c | 86 +++++++++++++++++-----------------------
1 file changed, 38 insertions(+), 48 deletions(-)
diff --git a/drivers/usb/serial/usb-serial.c b/drivers/usb/serial/usb-serial.c
index 4753c00..74b6f08 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@...uxfoundation.org>"
@@ -49,7 +50,7 @@
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);
@@ -61,59 +62,52 @@ static LIST_HEAD(usb_serial_driver_list);
struct usb_serial *usb_serial_get_by_index(unsigned index)
{
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, index);
mutex_unlock(&table_lock);
+ if (!port)
+ return NULL;
+
+ serial = port->serial;
+ kref_get(&serial->kref);
return serial;
}
-static struct usb_serial *get_free_serial(struct usb_serial *serial,
- int num_ports, unsigned int *minor)
+static int get_free_port(struct usb_serial_port *port)
{
- unsigned int i, j;
- int good_spot;
-
- dev_dbg(&serial->interface->dev, "%s %d\n", __func__, num_ports);
+ int i;
- *minor = 0;
mutex_lock(&table_lock);
- for (i = 0; i < SERIAL_TTY_MINORS; ++i) {
- if (serial_table[i])
- continue;
+ i = idr_alloc(&serial_minors, port, 0, 0, GFP_KERNEL);
+ if (i < 0)
+ return -EEXIST;
+ port->number = i;
+ mutex_unlock(&table_lock);
+ return i;
+}
- 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;
+static int get_free_serial(struct usb_serial *serial, int num_ports,
+ unsigned int *minor)
+{
+ unsigned int i;
+ unsigned int x;
- *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) {
- serial_table[i] = serial;
- serial->port[j++]->number = i;
- }
- mutex_unlock(&table_lock);
- return serial;
+ dev_dbg(&serial->interface->dev, "%s %d\n", __func__, num_ports);
+
+ *minor = 0xffffffff;
+ for (i = 0; i < num_ports; ++i) {
+ x = get_free_port(serial->port[i]);
+ if (x < 0)
+ goto error;
+ if (*minor == 0xffffffff)
+ *minor = x;
}
- mutex_unlock(&table_lock);
- return NULL;
+ return 0;
+error:
+ // FIXME unwind the already allocated minors
+ return -ENODEV;
}
static void return_serial(struct usb_serial *serial)
@@ -122,7 +116,7 @@ static void return_serial(struct usb_serial *serial)
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]->number);
mutex_unlock(&table_lock);
}
@@ -1041,7 +1035,7 @@ static int usb_serial_probe(struct usb_interface *interface,
*/
serial->disconnected = 1;
- if (get_free_serial(serial, num_ports, &minor) == NULL) {
+ if (get_free_serial(serial, num_ports, &minor)) {
dev_err(ddev, "No more free serial devices\n");
goto probe_error;
}
@@ -1225,7 +1219,6 @@ 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);
@@ -1233,9 +1226,6 @@ 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__);
--
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