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Date: Sat, 8 Jun 2013 12:03:47 +0200
From: Johan Hovold <jhovold@...il.com>
To: Greg KH <gregkh@...uxfoundation.org>
Cc: Tobias Winter <tobias@...uxdingsda.de>,
Bjørn Mork <bjorn@...k.no>,
Rob Landley <rob@...dley.net>,
Johan Hovold <jhovold@...il.com>, linux-usb@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/3] USB: serial: make minor allocation dynamic
On Fri, Jun 07, 2013 at 11:04:28AM -0700, Greg KH wrote:
> From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Changes v2 - v3:
> - fixed up comments about usb_serial_get_by_minor()
> - fixed error case in usb_serial_get_by_minor()
> - folded get_free_port() into get_free_serial()
> - renamed get_free_serial() to allocate_minors()
> - fixed console.c build breakage
> - properly pass in minor port number to usb_serial_console_init()
> --- 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>"
> @@ -49,72 +50,64 @@
> 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 *serial = NULL;
This isn't necessary anymore.
> + struct usb_serial_port *port;
>
> mutex_lock(&table_lock);
> - serial = serial_table[index];
> + port = idr_find(&serial_minors, minor);
> + if (!port)
> + goto exit;
>
> - if (serial) {
> - mutex_lock(&serial->disc_mutex);
> - if (serial->disconnected) {
> - mutex_unlock(&serial->disc_mutex);
> - serial = NULL;
> - } else {
> - kref_get(&serial->kref);
> - }
> + 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)
Perhaps rename this one release_minors to match allocate_minors (much
better name btw)?
> @@ -123,8 +116,9 @@ static void return_serial(struct usb_ser
>
> 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;
This isn't strictly needed as the serial struct release_serial is only
called once when the struct is about to be freed.
> }
>
> static void destroy_serial(struct kref *kref)
> @@ -136,7 +130,7 @@ static void destroy_serial(struct kref *
> serial = to_usb_serial(kref);
>
> /* return the minor range that this device had */
> - if (serial->minor != SERIAL_TTY_NO_MINOR)
> + if (serial->minors_reserved)
> return_serial(serial);
>
> if (serial->attached && serial->type->release)
All three patches look good otherwise. The port-number disambiguation
was indeed long overdue. Feel free to add
Reviewed-by: Johan Hovold <jhovold@...il.com>
Thanks,
Johan
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