From mboxrd@z Thu Jan 1 00:00:00 1970 From: Greg KH Subject: Re: [Patch V4 1/3] usb: Add Xen pvUSB protocol description Date: Fri, 24 Jul 2015 11:57:47 -0700 Message-ID: <20150724185747.GB21453@kroah.com> References: <1435042405-14235-1-git-send-email-jgross@suse.com> <1435042405-14235-2-git-send-email-jgross@suse.com> <20150722234640.GA29425@kroah.com> <55B067D7.3030904@suse.com> <20150723043653.GA31524@kroah.com> <55B08DB9.60902@suse.com> <20150723190801.GC11060@kroah.com> <55B1B628.7090200@suse.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <55B1B628.7090200-IBi9RG/b67k@public.gmane.org> Sender: linux-usb-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Juergen Gross Cc: linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, xen-devel-GuqFBffKawuULHF6PoxzQEEOCMrvLtNR@public.gmane.org, konrad.wilk-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org, david.vrabel-Sxgqhf6Nn4DQT0dZR+AlfA@public.gmane.org, boris.ostrovsky-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org, linux-usb-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: xen-devel@lists.xenproject.org On Fri, Jul 24, 2015 at 05:51:04AM +0200, Juergen Gross wrote: > On 07/23/2015 09:08 PM, Greg KH wrote: > >On Thu, Jul 23, 2015 at 08:46:17AM +0200, Juergen Gross wrote: > >>On 07/23/2015 06:36 AM, Greg KH wrote: > >>>On Thu, Jul 23, 2015 at 06:04:39AM +0200, Juergen Gross wrote: > >>>>On 07/23/2015 01:46 AM, Greg KH wrote: > >>>>>On Tue, Jun 23, 2015 at 08:53:23AM +0200, Juergen Gross wrote: > >>>>>>Add the definition of pvUSB protocol used between the pvUSB frontend in > >>>>>>a Xen domU and the pvUSB backend in a Xen driver domain (usually Dom0). > >>>>>> > >>>>>>This header was originally provided by Fujitsu for Xen based on Linux > >>>>>>2.6.18. > >>>>>> > >>>>>>Changes are: > >>>>>>- adapt to Linux style guide > >>>>>> > >>>>>>Signed-off-by: Juergen Gross > >>>>>>--- > >>>>>> include/xen/interface/io/usbif.h | 252 +++++++++++++++++++++++++++++++++++++++ > >>>>> > >>>>>Why is this a different interface than the existing ones we have today > >>>>>(i.e. usbip?) Where is it documented? Do the Xen developers / > >>>> > >>>>The interface definition is living in the Xen git repository for several > >>>>years now: > >>>> > >>>>git://xenbits.xen.org/xen.git -> xen/include/public/io/usbif.h > >>> > >>>That's header file, not a document describing the api here. > >> > >>I suppose you want to tell me I should add something like: > >> > >>Documentation/DocBook/usb/API-struct-urb.html > > > >Somewhere that people can refer to that describes this public-facing API > >that "must not ever be broken or changed". If you want to put it in a > >documentation file, or a .h file, I don't care. > > > >>>>It is used e.g. in SUSE's xen kernel since 2.6.18. > >>> > >>>I am very aware of the amount of Xen crap in SuSE's kernel, don't use > >>>that as an excuse for me to merge it to mainline :) > >> > >>:-) > >> > >>Wasn't meant as an excuse, just a hint why the interface can't be the > >>same as for usbip. We have to ensure compatibility with those kernels > > > >This shouldn't be a kernel/kernel compability issue, as the api talks > >between Xen and the OS, not between different OSs, right? > > Depends on where the backend is living. It's the backend the frontend is > talking to. > > There is a backend in SUSE's kernels up to SLE12. So compatibility is > to be maintained to those kernels. Note, just because a distro merged an out of tree patch, does not mean that mainline has to accept the same api as-is :) > Looks as if in future there will be one in qemu. So there's only one other backend talking to this, in one distro? > >>and possibly other operating systems (BSD?, Windows?) which already > >>might be using pvUSB with a Dom0 based on the SUSE xen kernel. > > > >Are there other operating system drivers today that use this API? Is > >this an API in the Xen core today that we have to support? > > Yes. Yes to both? Which other operating systems have such a driver? > >Some more background / descriptions would be nice to have. > > I guess a documentation file giving a brief explanation about the > interfaces of Xen wouldn't be a bad idea. This could avoid discussions > like this. Yes it would. > It shouldn't define each interface, but the classes of interfaces which > are existing (between kernel and hypervisor, frontends and backends) > and the stability requirements. Headers like the one we are discussing > here could then refer to this document. Why shouldn't the protocol be documented? thanks, greg k-h -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html