[ Upstream commit bcacbf06c8 ]
Currently the composite driver encodes the MaxPower field of
the configuration descriptor by reading the c->MaxPower of the
usb_configuration only if it is non-zero, otherwise it falls back
to using the value hard-coded in CONFIG_USB_GADGET_VBUS_DRAW.
However, there are cases when a configuration must explicitly set
bMaxPower to 0, particularly if its bmAttributes also has the
Self-Powered bit set, which is a valid combination.
This is specifically called out in the USB PD specification section
9.1, in which a PDUSB device "shall report zero in the bMaxPower
field after negotiating a mutually agreeable Contract", and also
verified by the USB Type-C Functional Test TD.4.10.2 Sink Power
Precedence Test.
The fix allows the c->MaxPower to be used for encoding the bMaxPower
even if it is 0, if the self-powered bit is also set. An example
usage of this would be for a ConfigFS gadget to be dynamically
updated by userspace when the Type-C connection is determined to be
operating in Power Delivery mode.
Co-developed-by: Ronak Vijay Raheja <rraheja@codeaurora.org>
Acked-by: Felipe Balbi <balbi@kernel.org>
Signed-off-by: Ronak Vijay Raheja <rraheja@codeaurora.org>
Signed-off-by: Jack Pham <jackp@codeaurora.org>
Link: https://lore.kernel.org/r/20210720080907.30292-1-jackp@codeaurora.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
03f4492dbf