From: Oliver Neukum <oneukum@suse.com>
To: "Lukáš Lalinský" <lukas@oxygene.sk>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org
Subject: Re: [PATCH] USB: Add quirk for WORLDE easykey.25 MIDI keyboard
Date: Tue, 24 Jan 2017 09:30:51 +0100 [thread overview]
Message-ID: <1485246651.12785.4.camel@suse.com> (raw)
In-Reply-To: <CAGUtLj8cWp-WPx8up90CHYDJ-Xvgc6Wmb3FsQYnn_ThY4htOPw@mail.gmail.com>
Am Dienstag, den 24.01.2017, 08:37 +0100 schrieb Lukáš Lalinský:
> On Tue, Jan 24, 2017 at 8:32 AM, Oliver Neukum <oneukum@suse.com>
> wrote:
> >
> > Am Montag, den 23.01.2017, 19:36 +0100 schrieb Lukáš Lalinský:
> > >
> > > I have uploaded both captures here -
> > > https://gist.github.com/lalinsky/83148a827d5cd43e79e377d8e1b5ed0d
> >
> > 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
True.
> 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.
Regards
Oliver
next prev parent reply other threads:[~2017-01-24 8:31 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-20 18:46 [PATCH] USB: Add quirk for WORLDE easykey.25 MIDI keyboard Lukáš Lalinský
2017-01-21 9:08 ` Greg Kroah-Hartman
2017-01-23 18:36 ` Lukáš Lalinský
2017-01-24 7:32 ` Oliver Neukum
2017-01-24 7:37 ` Lukáš Lalinský
2017-01-24 8:30 ` Oliver Neukum [this message]
2017-01-24 8:31 ` Lukáš Lalinský
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