Re: [PATCH] [RFC] usb: gadget: hid: Add "single_ep" option

[Felipe Balbi <balbi@kernel.org>]

Hi,

Benjamin Herrenschmidt <benh@kernel.crashing.org> writes:

> On Fri, 2019-08-09 at 08:31 +0300, Felipe Balbi wrote:
>> Hi,
>> 
>> Benjamin Herrenschmidt <benh@kernel.crashing.org> writes:
>> 
>> > Some host drivers really do not like keyboards having an OUT
>> > endpoint.
>> > 
>> > For example, most UEFI forked from EDK2 before 2006 (or was it 2008
>> > ?)
>> > have a bug, they'll try to use the *last* interrupt EP in the
>> > descriptor list and just assume it's an IN endpoint. Newer UEFIs
>> > use the *first* interrupt endpoint instead. None of them checks the
>> > direction :-(
>> > 
>> > This adds a "single_ep" option to f_hid which allows to specify
>> > that
>> > only the IN path should be created. This should be used for
>> > keyboards
>> > if they are ever to be used with such systems as host.
>> > 
>> > Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
>> 
>> Could you come up with a slightly more descriptive name? single_ep
>> doesn't give me any hint of which endpoint will be left around.
>> 
>> Perhaps call it 'disable_output_report'?
>
> Sure. Or more concice "input_only" maybe ?

that works too. Another option would to introduce two options,
has_input_report and has_output_report and have them true by default.

Then user can even produce an output-only HID device, like these odd
USB-controlled relays.

-- 
balbi