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USB: don't send Set-Interface after reset

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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>
This commit is contained in:
Alan Stern 2009-02-26 10:21:02 -05:00 committed by Greg Kroah-Hartman
parent 77aa2b5878
commit 4fe0387afa
1 changed files with 16 additions and 7 deletions
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23
drivers/usb/core/hub.c
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@ -3393,10 +3393,10 @@ static int usb_reset_and_verify_device(struct usb_device *udev)
udev->descriptor = descriptor; /* for disconnect() calls */
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;
ret = usb_set_interface(udev, desc->bInterfaceNumber,
desc->bAlternateSetting);
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",