946ef68ad4
Some UDC drivers (like the DWC3) expect that the response to a setup() request is queued from within the setup function itself so that it is available as soon as setup() has completed. Upon receiving a setup request the function fs driver creates an event that is made available to userspace. And only once userspace has acknowledged that event the response to the setup request is queued. So it violates the requirement of those UDC drivers and random failures can be observed. This is basically a race condition and if userspace is able to read the event and queue the response fast enough all is good. But if it is not, for example because other processes are currently scheduled to run, the USB host that sent the setup request will observe an error. To avoid this the gadget framework provides the USB_GADGET_DELAYED_STATUS return code. If a setup() callback returns this value the UDC driver is aware that response is not yet available and can uses the appropriate methods to handle this case. Since in the case of function fs the response will never be available when the setup() function returns make sure that this status code is used. This fixed random occasional failures that were previously observed on a DWC3 based system under high system load. Signed-off-by: Lars-Peter Clausen <lars@metafoo.de> Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.