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usbcore: help drivers to change device configs

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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: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Alan Stern 2006-08-21 12:08:19 -04:00 committed by Greg Kroah-Hartman
parent 3a3416b12f
commit 088dc270e1
2 changed files with 62 additions and 0 deletions
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59
drivers/usb/core/message.c
View File

@ -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);

3
include/linux/usb.h
View File

@ -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