USB: UDC core: Add udc_async_callbacks gadget op
The Gadget API has a theoretical race when a gadget driver is unbound. Although the pull-up is turned off before the driver's ->unbind callback runs, if the USB cable were to be unplugged at just the wrong moment there would be nothing to prevent the UDC driver from invoking the ->disconnect callback after the unbind has finished. In theory, other asynchronous callbacks could also happen during the time before the UDC driver's udc_stop routine is called, and the gadget driver would not be prepared to handle any of them. We need a way to tell UDC drivers to stop issuing asynchronous (that is, ->suspend, ->resume, ->disconnect, ->reset, or ->setup) callbacks at some point after the pull-up has been turned off and before the ->unbind callback runs. This patch adds a new ->udc_async_callbacks callback to the usb_gadget_ops structure for precisely this purpose, and it adds the corresponding support to the UDC core. Later patches in this series add support for udc_async_callbacks to several UDC drivers. Acked-by:Felipe Balbi <balbi@kernel.org> Signed-off-by:
Alan Stern <stern@rowland.harvard.edu> Link: https://lore.kernel.org/r/20210520202144.GC1216852@rowland.harvard.edu Signed-off-by:
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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