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[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: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
hifive-unleashed-5.1
David Brownell 2005-04-18 17:39:25 -07:00 committed by Greg K-H
parent 45f23f189c
commit a81e7ecca3
1 changed files with 4 additions and 21 deletions
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25
drivers/usb/core/message.c
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@ -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.