4d644abf25
Commit 1b9ba000 ("Allow function drivers to pause control
transfers") states that USB_GADGET_DELAYED_STATUS is only
supported if data phase is 0 bytes.
It seems that when the length is not 0 bytes, there is no
need to explicitly delay the data stage since the transfer
is not completed until the user responds. However, when the
length is 0, there is no data stage and the transfer is
finished once setup() returns, hence there is a need to
explicitly delay completion.
This manifests as the following bugs:
Prior to 946ef68ad4e4 ('Let setup() return
USB_GADGET_DELAYED_STATUS'), when setup is 0 bytes, ffs
would require user to queue a 0 byte request in order to
clear setup state. However, that 0 byte request was actually
not needed and would hang and cause errors in other setup
requests.
After the above commit, 0 byte setups work since the gadget
now accepts empty queues to ep0 to clear the delay, but all
other setups hang.
Fixes: 946ef68ad4e4 ("Let setup() return USB_GADGET_DELAYED_STATUS")
Signed-off-by: Jerry Zhang <zhangjerry@google.com>
Cc: stable <stable@vger.kernel.org>
Acked-by: Felipe Balbi <felipe.balbi@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
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https://www.kernel.org/doc/html/latest/
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.