USB: don't send Set-Interface after reset (4fe0387a) · Commits · 戴 / test

This patch (as1221) changes the way usbcore reinitializes a device following a reset or a reset-resume. Currently we call usb_set_interface() for every interface in the active configuration; this is to put the interface into the same altsetting as before the reset and to make sure that the host's endpoint state matches the device's endpoint state. However, sending a Set-Interface request is a waste of time if an interface was already in altsetting 0 before the reset, since it is certainly in altsetting 0 afterward. In addition, many devices can't handle Set-Interface requests -- they crash when they receive them. So instead, the patch adds code to check each interface. If the interface wasn't in altsetting 0 before the reset, we go head with the Set-Interface request as before. But if it was then we skip sending the Set-Interface request, and we clear out the host-side endpoint state by calling usb_disable_interface() followed by usb_enable_interface(). The patch also adds a couple of new comments to explain what's going on. Signed-off-by:

Alan Stern <stern@rowland.harvard.edu> Signed-off-by:

Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/core/hub.c

+16 −7

Original line number	Diff line number	Diff line
		@@ -3394,9 +3394,9 @@ static int usb_reset_and_verify_device(struct usb_device *udev)
		goto re_enumerate;
		}

		/* Restore the device's previous configuration */
		if (!udev->actconfig)
		goto done;

		ret = usb_control_msg(udev, usb_sndctrlpipe(udev, 0),
		USB_REQ_SET_CONFIGURATION, 0,
		udev->actconfig->desc.bConfigurationValue, 0,
		@@ -3409,16 +3409,25 @@ static int usb_reset_and_verify_device(struct usb_device *udev)
		}
		usb_set_device_state(udev, USB_STATE_CONFIGURED);

		/* Put interfaces back into the same altsettings as before.
		* Don't bother to send the Set-Interface request for interfaces
		* that were already in altsetting 0; besides being unnecessary,
		* many devices can't handle it. Instead just reset the host-side
		* endpoint state.
		*/
		for (i = 0; i < udev->actconfig->desc.bNumInterfaces; i++) {
		struct usb_interface *intf = udev->actconfig->interface[i];
		struct usb_interface_descriptor *desc;

		/* set_interface resets host side toggle even
		* for altsetting zero. the interface may have no driver.
		*/
		desc = &intf->cur_altsetting->desc;
		if (desc->bAlternateSetting == 0) {
		usb_disable_interface(udev, intf, true);
		usb_enable_interface(udev, intf, true);
		ret = 0;
		} else {
		ret = usb_set_interface(udev, desc->bInterfaceNumber,
		desc->bAlternateSetting);
		}
		if (ret < 0) {
		dev_err(&udev->dev, "failed to restore interface %d "
		"altsetting %d (error=%d)\n",

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