linux/drivers/usb/core/file.c
Ivan Orlov 015fbddefc USB: make usb class a const structure
Now that the driver core allows for struct class to be in read-only
memory, remove the usb_class structure and create the usbmisc_class
const class structure declared at build time which places it into
read-only memory, instead of having it to be dynamically allocated
at load time.

Additionally, now we register usb class at startup and unregister it
when shutting down, so we don't have to count uses of the class.
Therefore we don't need the 'usb_class' structure anymore. Due to this
fact, remove all static functions related to class initialization and
deinitialization. We can't use them in 'usb.c' since they are static
and we don't really need them anymore.

Since we have to register the class in usb_init function in 'usb.c'
and use it in 'file.c' as well, declare the usbmisc_class structure
as 'export' in the 'usb.h' file.

Debatable moment: the class registration and unregistration functions
could be extracted to the 'file.c'. I think we don't want to do this
since it would be one-line functions. They would make the code paths
more confusing and add calling overhead.

Suggested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ivan Orlov <ivan.orlov0322@gmail.com>
Link: https://lore.kernel.org/r/20230621202514.1223670-1-ivan.orlov0322@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2023-07-25 17:49:30 +02:00

194 lines
5.1 KiB
C

// SPDX-License-Identifier: GPL-2.0
/*
* drivers/usb/core/file.c
*
* (C) Copyright Linus Torvalds 1999
* (C) Copyright Johannes Erdfelt 1999-2001
* (C) Copyright Andreas Gal 1999
* (C) Copyright Gregory P. Smith 1999
* (C) Copyright Deti Fliegl 1999 (new USB architecture)
* (C) Copyright Randy Dunlap 2000
* (C) Copyright David Brownell 2000-2001 (kernel hotplug, usb_device_id,
* more docs, etc)
* (C) Copyright Yggdrasil Computing, Inc. 2000
* (usb_device_id matching changes by Adam J. Richter)
* (C) Copyright Greg Kroah-Hartman 2002-2003
*
* Released under the GPLv2 only.
*/
#include <linux/module.h>
#include <linux/errno.h>
#include <linux/rwsem.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/usb.h>
#include "usb.h"
#define MAX_USB_MINORS 256
static const struct file_operations *usb_minors[MAX_USB_MINORS];
static DECLARE_RWSEM(minor_rwsem);
static int usb_open(struct inode *inode, struct file *file)
{
int err = -ENODEV;
const struct file_operations *new_fops;
down_read(&minor_rwsem);
new_fops = fops_get(usb_minors[iminor(inode)]);
if (!new_fops)
goto done;
replace_fops(file, new_fops);
/* Curiouser and curiouser... NULL ->open() as "no device" ? */
if (file->f_op->open)
err = file->f_op->open(inode, file);
done:
up_read(&minor_rwsem);
return err;
}
static const struct file_operations usb_fops = {
.owner = THIS_MODULE,
.open = usb_open,
.llseek = noop_llseek,
};
static char *usb_devnode(const struct device *dev, umode_t *mode)
{
struct usb_class_driver *drv;
drv = dev_get_drvdata(dev);
if (!drv || !drv->devnode)
return NULL;
return drv->devnode(dev, mode);
}
const struct class usbmisc_class = {
.name = "usbmisc",
.devnode = usb_devnode,
};
int usb_major_init(void)
{
int error;
error = register_chrdev(USB_MAJOR, "usb", &usb_fops);
if (error)
printk(KERN_ERR "Unable to get major %d for usb devices\n",
USB_MAJOR);
return error;
}
void usb_major_cleanup(void)
{
unregister_chrdev(USB_MAJOR, "usb");
}
/**
* usb_register_dev - register a USB device, and ask for a minor number
* @intf: pointer to the usb_interface that is being registered
* @class_driver: pointer to the usb_class_driver for this device
*
* This should be called by all USB drivers that use the USB major number.
* If CONFIG_USB_DYNAMIC_MINORS is enabled, the minor number will be
* dynamically allocated out of the list of available ones. If it is not
* enabled, the minor number will be based on the next available free minor,
* starting at the class_driver->minor_base.
*
* This function also creates a usb class device in the sysfs tree.
*
* usb_deregister_dev() must be called when the driver is done with
* the minor numbers given out by this function.
*
* Return: -EINVAL if something bad happens with trying to register a
* device, and 0 on success.
*/
int usb_register_dev(struct usb_interface *intf,
struct usb_class_driver *class_driver)
{
int retval = 0;
int minor_base = class_driver->minor_base;
int minor;
char name[20];
#ifdef CONFIG_USB_DYNAMIC_MINORS
/*
* We don't care what the device tries to start at, we want to start
* at zero to pack the devices into the smallest available space with
* no holes in the minor range.
*/
minor_base = 0;
#endif
if (class_driver->fops == NULL)
return -EINVAL;
if (intf->minor >= 0)
return -EADDRINUSE;
dev_dbg(&intf->dev, "looking for a minor, starting at %d\n", minor_base);
down_write(&minor_rwsem);
for (minor = minor_base; minor < MAX_USB_MINORS; ++minor) {
if (usb_minors[minor])
continue;
usb_minors[minor] = class_driver->fops;
intf->minor = minor;
break;
}
if (intf->minor < 0) {
up_write(&minor_rwsem);
return -EXFULL;
}
/* create a usb class device for this usb interface */
snprintf(name, sizeof(name), class_driver->name, minor - minor_base);
intf->usb_dev = device_create(&usbmisc_class, &intf->dev,
MKDEV(USB_MAJOR, minor), class_driver,
"%s", kbasename(name));
if (IS_ERR(intf->usb_dev)) {
usb_minors[minor] = NULL;
intf->minor = -1;
retval = PTR_ERR(intf->usb_dev);
}
up_write(&minor_rwsem);
return retval;
}
EXPORT_SYMBOL_GPL(usb_register_dev);
/**
* usb_deregister_dev - deregister a USB device's dynamic minor.
* @intf: pointer to the usb_interface that is being deregistered
* @class_driver: pointer to the usb_class_driver for this device
*
* Used in conjunction with usb_register_dev(). This function is called
* when the USB driver is finished with the minor numbers gotten from a
* call to usb_register_dev() (usually when the device is disconnected
* from the system.)
*
* This function also removes the usb class device from the sysfs tree.
*
* This should be called by all drivers that use the USB major number.
*/
void usb_deregister_dev(struct usb_interface *intf,
struct usb_class_driver *class_driver)
{
if (intf->minor == -1)
return;
dev_dbg(&intf->dev, "removing %d minor\n", intf->minor);
device_destroy(&usbmisc_class, MKDEV(USB_MAJOR, intf->minor));
down_write(&minor_rwsem);
usb_minors[intf->minor] = NULL;
up_write(&minor_rwsem);
intf->usb_dev = NULL;
intf->minor = -1;
}
EXPORT_SYMBOL_GPL(usb_deregister_dev);