From 088dc270e1da03744d977cbd9edd4311af142348 Mon Sep 17 00:00:00 2001
From: Alan Stern <stern@rowland.harvard.edu>
Date: Mon, 21 Aug 2006 12:08:19 -0400
Subject: [PATCH] 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: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---
drivers/usb/core/message.c | 59 ++++++++++++++++++++++++++++++++++++++
include/linux/usb.h | 3 ++
2 files changed, 62 insertions(+)
diff --git a/drivers/usb/core/message.c b/drivers/usb/core/message.c
index 49cfd7928a1c7c..333b22c68aa4f3 100644
--- a/drivers/usb/core/message.c
+++ b/drivers/usb/core/message.c
@@ -1493,6 +1493,65 @@ free_interfaces:
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);
diff --git a/include/linux/usb.h b/include/linux/usb.h
index 26d8a5f36896a7..f104efa04d797e 100644
--- a/include/linux/usb.h
+++ b/include/linux/usb.h
@@ -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
--
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