Commit a81e7ecc authored by David Brownell's avatar David Brownell Committed by Greg K-H
Browse files

[PATCH] USB: revert "fix" to usb_set_interface() 



This reverts a recent change to usb_set_interface().  The change worked
around a quirk in certain devices, but doing this in usbcore creates
needless regressions for other devices.  More appropriate fixes won't
put such handling in usbcore.

Basically it's tricky to do a full software reset of USB device state, since
the devices don't all act the same.  This adds a note to the kerneldoc for
the usb_reset_configuration() call to highlight the quirk this was working
around:  endpoint data toggles not being reset.

Signed-off-by: default avatarDavid Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent 45f23f18

drivers/usb/core/message.c

+4 −21
Original line number Diff line number Diff line
@@ -1133,29 +1133,10 @@ int usb_set_interface(struct usb_device *dev, int interface, int alternate) 
	/* prevent submissions using previous endpoint settings */

	usb_disable_interface(dev, iface);



	/* 9.1.1.5 says:

	 *

	 *	Configuring a device or changing an alternate setting

	 *	causes all of the status and configuration values

	 *	associated with endpoints in the affected interfaces to

	 *	be set to their default values. This includes setting

	 *	the data toggle of any endpoint using data toggles to

	 *	the value DATA0.

	 *

	 * Some devices take this too literally and don't reset the data

	 * toggles if the new altsetting is the same as the old one (the

	 * command isn't "changing" an alternate setting).  We will manually

	 * reset the toggles when the new and old altsettings are the same.

	 * Most devices won't need this, but fortunately it doesn't happen

	 * often.

	 */

	if (iface->cur_altsetting == alt)

		manual = 1;

	iface->cur_altsetting = alt;



	/* If the interface only has one altsetting and the device didn't

	 * accept the request (or whenever the old altsetting is the same

	 * as the new one), we attempt to carry out the equivalent action

	 * accept the request, we attempt to carry out the equivalent action

	 * by manually clearing the HALT feature for each endpoint in the

	 * new altsetting.

	 */
@@ -1202,7 +1183,9 @@ int usb_set_interface(struct usb_device *dev, int interface, int alternate) 
 *

 * Because this affects multiple interfaces, avoid using this with composite

 * (multi-interface) devices.  Instead, the driver for each interface may

 * use usb_set_interface() on the interfaces it claims.  Resetting the whole

 * use usb_set_interface() on the interfaces it claims.  Be careful though;

 * some devices don't support the SET_INTERFACE request, and others won't

 * reset all the interface state (notably data toggles).  Resetting the whole

 * configuration would affect other drivers' interfaces.

 *

 * The caller must own the device lock.

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