linux-kernel - Re: [PATCH] usb-core: Add MS_INTR

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Date:   Mon, 13 Mar 2017 21:44:45 -0400 (EDT)
From:   Alan Stern <stern@...land.harvard.edu>
To:     Samuel Thibault <samuel.thibault@...-lyon.org>
cc:     Dave Mielke <dave@...lke.cc>, <gregkh@...uxfoundation.org>,
        <linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <kevin.derome@...tech.eu>, <clause.andreabush@...il.com>,
        <mengualjeanphi@...e.fr>
Subject: Re: [PATCH] usb-core: Add MS_INTR_BINTERVAL USB quirk

On Mon, 13 Mar 2017, Samuel Thibault wrote:

> Alan Stern, on dim. 12 mars 2017 21:40:33 -0400, wrote:
> > On Sun, 12 Mar 2017, Dave Mielke wrote:
> > > [quoted lines by Alan Stern on 2017/03/12 at 21:31 -0400]
> > > 
> > > >A device's speed is only partially related to its USB version.  A
> > > >USB-1.1 device can run at low speed or full speed.  A USB-2 device can
> > > >run at low, full, or high speed.  And a USB-3 device can run at low,
> > > >full, high, or Super speed.
> > > 
> > > Yes, I did know this, so maybe I misunderstood what you were wondering about. 
> > > Were you wondering why 64ms was too long?
> > 
> > No, I was wondering why an HID device would run at high speed.  Both
> > you and Samuel implied that this was because it was a USB-2 device.  
> > But that is not an adequate answer, because it is perfectly valid for a 
> > USB-2 device to run at full speed.
> 
> to_usb_device(ddev)->speed really is USB_SPEED_HIGH, otherwise the quirk
> wouldn't work :)

Indeed; I believe you.  It's just odd and a little noteworthy, that's
all.

Alan Stern