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Subject[PATCH] USB: Only enable autosuspend by default on certain device classes
We're seeing a large number of problems with devices not appreciating 
USB autosuspend, especially printers and scanners. According to
http://www.microsoft.com/whdc/system/bus/USB/USBFAQ_intro.mspx only a
subset of drivers support it in Windows XP, meaning that most devices
are probably untested in this situation. This patch alters the behaviour
to match that of Windows. Userspace can still whitelist devices as
appropriate, and the set of classes supporting autosuspend probably
covers pretty much every driver likely to be found on any portable
device.

Signed-off-by: Matthew Garrett <mjg59@srcf.ucam.org>

---
diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index caaa46f..12ba789 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -1278,6 +1278,22 @@ int usb_new_device(struct usb_device *udev)
{
int err;

+#ifdef CONFIG_USB_SUSPEND
+ /* Disable autosuspend for most devices - Windows only enables it
+ for a small subset of classes, so most hardware hasn't been tested
+ with it. Userspace can always reenable at a later point */
+
+ switch (udev->descriptor.bDeviceClass) {
+ case USB_CLASS_HID:
+ case USB_CLASS_COMM:
+ case USB_CLASS_WIRELESS_CONTROLLER:
+ case USB_CLASS_HUB:
+ break;
+ default:
+ udev->autosuspend_disabled = 1;
+ }
+#endif
+
/* Determine quirks */
usb_detect_quirks(udev);

--
Matthew Garrett | mjg59@srcf.ucam.org
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