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Commit 088dc270 authored by Alan Stern's avatar Alan Stern Committed by Greg Kroah-Hartman
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usbcore: help drivers to change device configs 



It's generally a bad idea for USB interface drivers to try to change a
device's configuration, and usbcore doesn't provide any way for them
to do it.  However in a few exceptional circumstances it can make
sense.  This patch (as767) adds a roundabout mechanism to help drivers
that may need it.

Signed-off-by: default avatarAlan Stern <stern@rowland.harvard.edu>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent 3a3416b1

drivers/usb/core/message.c

+59 −0
Original line number Diff line number Diff line
@@ -1493,6 +1493,65 @@ int usb_set_configuration(struct usb_device *dev, int configuration) 
	return 0;

}



struct set_config_request {

	struct usb_device	*udev;

	int			config;

	struct work_struct	work;

};



/* Worker routine for usb_driver_set_configuration() */

static void driver_set_config_work(void *_req)

{

	struct set_config_request *req = _req;



	usb_lock_device(req->udev);

	usb_set_configuration(req->udev, req->config);

	usb_unlock_device(req->udev);

	usb_put_dev(req->udev);

	kfree(req);

}



/**

 * usb_driver_set_configuration - Provide a way for drivers to change device configurations

 * @udev: the device whose configuration is being updated

 * @config: the configuration being chosen.

 * Context: In process context, must be able to sleep

 *

 * Device interface drivers are not allowed to change device configurations.

 * This is because changing configurations will destroy the interface the

 * driver is bound to and create new ones; it would be like a floppy-disk

 * driver telling the computer to replace the floppy-disk drive with a

 * tape drive!

 *

 * Still, in certain specialized circumstances the need may arise.  This

 * routine gets around the normal restrictions by using a work thread to

 * submit the change-config request.

 *

 * Returns 0 if the request was succesfully queued, error code otherwise.

 * The caller has no way to know whether the queued request will eventually

 * succeed.

 */

int usb_driver_set_configuration(struct usb_device *udev, int config)

{

	struct set_config_request *req;



	req = kmalloc(sizeof(*req), GFP_KERNEL);

	if (!req)

		return -ENOMEM;

	req->udev = udev;

	req->config = config;

	INIT_WORK(&req->work, driver_set_config_work, req);



	usb_get_dev(udev);

	if (!schedule_work(&req->work)) {

		usb_put_dev(udev);

		kfree(req);

		return -EINVAL;

	}

	return 0;

}

EXPORT_SYMBOL_GPL(usb_driver_set_configuration);



// synchronous request completion model

EXPORT_SYMBOL(usb_control_msg);

EXPORT_SYMBOL(usb_bulk_msg);

include/linux/usb.h

+3 −0
Original line number Diff line number Diff line
@@ -1099,6 +1099,9 @@ extern int usb_clear_halt(struct usb_device *dev, int pipe); 
extern int usb_reset_configuration(struct usb_device *dev);

extern int usb_set_interface(struct usb_device *dev, int ifnum, int alternate);



/* this request isn't really synchronous, but it belongs with the others */

extern int usb_driver_set_configuration(struct usb_device *udev, int config);



/*

 * timeouts, in milliseconds, used for sending/receiving control messages

 * they typically complete within a few frames (msec) after they're issued