On Mon, Aug 31, 2020 at 02:46:49PM +0300, Mathias Nyman wrote:
> Userspace drivers that use a SetConfiguration() request to "lightweight"
> reset a already configured usb device might cause data toggles to get out
> of sync between the device and host, and the device becomes unusable.
>
> The xHCI host requires endpoints to be dropped and added back to reset the
> toggle. USB core avoids these otherwise extra steps if the current active
> configuration is the same as the new requested configuration.
You should mention usb_reset_configuration() here. After all, that's
where most of the changes in this patch occur.
>
> A SetConfiguration() request will reset the device side data toggles.
> Make sure usb core drops and adds back the endpoints in this case.
>
> To avoid code duplication split the current usb_disable_device() function
> and reuse the endpoint specific part.
>
> Cc: stable <stable@xxxxxxxxxxxxxxx>
> Tested-by: Martin Thierer <mthierer@xxxxxxxxx>
> Signed-off-by: Mathias Nyman <mathias.nyman@xxxxxxxxxxxxxxx>
> ---
> @@ -1589,8 +1579,12 @@ int usb_reset_configuration(struct usb_device *dev)
> USB_REQ_SET_CONFIGURATION, 0,
> config->desc.bConfigurationValue, 0,
> NULL, 0, USB_CTRL_SET_TIMEOUT);
> - if (retval < 0)
> - goto reset_old_alts;
> + if (retval < 0) {
> + retval = usb_hcd_alloc_bandwidth(dev, NULL, NULL, NULL);
> + usb_enable_lpm(dev);
> + mutex_unlock(hcd->bandwidth_mutex);
> + return retval;
That's not right; we want to return the original error code. Not 0,
which usb_hcd_alloc_bandwidth() will probably give us. Just remove
the "retval =" from the call above.
Alan Stern
