Messages in this thread | | | From | "Zengtao (B)" <> | Subject | RE: [PATCH] usb: hub: try old enumeration scheme first for high speed devices | Date | Tue, 14 Aug 2018 07:35:00 +0000 |
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Hi alan:
>-----Original Message----- >From: linux-usb-owner@vger.kernel.org >[mailto:linux-usb-owner@vger.kernel.org] On Behalf Of Alan Stern >Sent: Friday, August 10, 2018 10:20 PM >To: Roger Quadros <rogerq@ti.com> >Cc: Zengtao (B) <prime.zeng@hisilicon.com>; gregkh@linuxfoundation.org; >mathias.nyman@linux.intel.com; drinkcat@chromium.org; >felipe.balbi@linux.intel.com; drake@endlessm.com; mike.looijmans@topic.nl; >joe@perches.com; linux-usb@vger.kernel.org; linux-kernel@vger.kernel.org >Subject: Re: [PATCH] usb: hub: try old enumeration scheme first for high speed >devices > >On Fri, 10 Aug 2018, Roger Quadros wrote: > >> Hi, >> >> On 10/08/18 18:01, Zeng Tao wrote: >> > The new scheme is required just to support legacy low and full-speed >> > devices. For high speed devices, it will slower the enumeration speed. >> > So in this patch we try the "old" enumeration scheme first for high >> > speed devices. >> >> How slow does it get? Is it significant? >> Do we risk breaking existing HS devices that work? I don't think we >> can be sure till we run this through testing. > >Indeed. I am extremely skeptical about a patch like this, unless somebody can >show that Windows uses the "old" scheme for high-speed devices.
Yes, this is what the windows has done, you can refer to https://blogs.msdn.microsoft.com/usbcoreblog/2013/04/11/usb-2-1-2-0-1-1-device-enumeration-changes-in-windows-8/
> >Alan Stern
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