Re: [PATCH] USB: Add quirk for WORLDE easykey.25 MIDI keyboard

From: Oliver Neukum
Date: Tue Jan 24 2017 - 03:31:16 EST

Am Dienstag, den 24.01.2017, 08:37 +0100 schrieb LukÃÅ LalinskÃ:
> On Tue, Jan 24, 2017 at 8:32 AM, Oliver Neukum <oneukum@xxxxxxxx>
> wrote:
> >
> > Am Montag, den 23.01.2017, 19:36 +0100 schrieb LukÃÅ LalinskÃ:
> > >
> > > I have uploaded both captures here -
> > >
> >
> > Indeed it is does not set a configuration. Either the capture
> > is incomplete or device and host violate the standard. A device
> > may be left unconfigured.
> Is this may or may not? I'm not familiar with USB, so I assumed if

You can leave a device unconfigured. In that case it stays in the
addressed state, where its power draw is strictly limited.
That is exactly what the kernel does when it is confronted with
a device that would overdraw the power budget.

> there is only one configuration and there is always one active, it
> does not need to be set explicitly because the correct one is already
> active.

No, it is not. Or rather it should not be. Can you please recheck
that you are capturing the whole exchange?

> > We need to read the descriptors even if we
> > see only one configuration to get the power budgeting right.
> Aren't those in the CONFIGURATION descriptors? Reading the STRING


> descriptor is probably only useful if you need to print the
> configuration details somewhere.

Also true.

> >
> > Does the device work without any .ini file?
> Yes. It's a standard MIDI device, no configuration is required.

So Windows by default does not read string descriptors. That is worth
a thought, but we need to check. Yet I am not sure how useful that is.
The first lsusb would crash the device. We'd need a quirk anyway.