From: Juergen Gross <jgross@suse.com>
To: George Dunlap <george.dunlap@eu.citrix.com>,
Ian Campbell <ian.campbell@citrix.com>,
Ian Jackson <Ian.Jackson@eu.citrix.com>
Cc: Jim Fehlig <jfehlig@suse.com>, Simon Cao <caobosimon@gmail.com>,
Wei Liu <wei.liu2@citrix.com>, Chunyan Liu <cyliu@suse.com>,
"xen-devel@lists.xen.org" <xen-devel@lists.xen.org>
Subject: Re: [PATCH V4 3/7] libxl: add pvusb API
Date: Thu, 18 Jun 2015 15:03:05 +0200 [thread overview]
Message-ID: <5582C189.5010602@suse.com> (raw)
In-Reply-To: <5582B4BE.1070202@eu.citrix.com>
On 06/18/2015 02:08 PM, George Dunlap wrote:
> On 06/17/2015 12:24 PM, Ian Campbell wrote:
>> On Tue, 2015-06-16 at 12:44 +0100, Ian Jackson wrote:
>>> George Dunlap writes ("Re: [Xen-devel] [PATCH V4 3/7] libxl: add pvusb API"):
>>>> On Tue, Jun 16, 2015 at 12:19 PM, Juergen Gross <jgross@suse.com> wrote:
>>>>> I'm pretty sure this is just a matter of timing during boot: the busses
>>>>> are all (or at least some of them) queried at the same time and the
>>>>> first answering gets number 1, the next 2, and so on. And timing seems
>>>>> to be different enough to result in unstable bus numbers.
>>>>
>>>> Right -- I meant "stable in topology within one boot", but at least
>>>> two of you have now understood me to mean "across reboots" by default,
>>>> so that's obviously a detail that needs to be specified. :-)
>>>
>>> I think "stable in topology within one boot" is nearly vacuous (or are
>>> we expecting buses or devices to spontaneously renumber themselves for
>>> no reason) and also nearly useless.
>>>
>>> We definitely need _some_ way for a user to identify a specific device
>>> uniquely in a way that is reliable from one boot to the next. vid:pid
>>> is one way to do this, but not always sufficient.
>>
>> We should perhaps separate out the "end user" from the "libxl
>> user" (i.e. the toolstack application) in our deliberations here.
>>
>> We have the option of settling on a single way of describing a device to
>> libxl in the libxl API but allowing the toolstack to choose to present
>> the user with multiple different ways to specify things by providing a
>> suitable set of helper functions (in either libxlu or libxl proper) from
>> a variety of schemes to the one true way of describing a device.
>>
>> That sounds better to me than having the libxl API consist of the union
>> of all potentially useful ways to refer to a device.
>
> This was my original design. :-)
>
>> I'm not sure whether that also gives us the freedom to use something
>> which is only stable for a given boot at the libxl API layer though.
>
> I'm not sure why it doesn't -- as long as things don't change between
> the time the toostack converts a "stable name" into a specification and
> the time libxl uses it, it should be fine.
>
> One advantage of having a richer interface that Juergen pointed out
> previously was the ability to specify attaching devices automatically
> when they show yp; i.e., "If a device with this
> vendorid:deviceid:serialnumber shows up, please attach it to this VM".
>
> But we don't have that functionality now; and there's no reason we
> couldn't add extra ways of specifying devices in the future.
>
> This usb interface stuff is really becoming a morass. The core
> functionality is fairly independent of the interface. I'm inclined to
> say that we should start with a simple specification (only bus.addr),
> and try to get both pvusb and hvmusb in. Then we can talk about where
> to add additional specifications (including cross-boot stable
> specifcations).
+1
Juergen
next prev parent reply other threads:[~2015-06-18 13:03 UTC|newest]
Thread overview: 88+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-10 3:20 [PATCH V4 0/7] xen pvusb toolstack work Chunyan Liu
2015-06-10 3:20 ` [PATCH V4 1/7] libxl: export some functions for pvusb use Chunyan Liu
2015-06-11 16:08 ` Ian Jackson
2015-06-11 16:28 ` Wei Liu
2015-06-12 15:14 ` Ian Jackson
2015-06-10 3:20 ` [PATCH V4 2/7] libxl_read_file_contents: add new entry to read sysfs file Chunyan Liu
2015-06-11 16:16 ` Ian Jackson
2015-06-12 7:00 ` Chun Yan Liu
2015-06-12 15:11 ` Ian Jackson
2015-06-10 3:20 ` [PATCH V4 3/7] libxl: add pvusb API Chunyan Liu
2015-06-11 15:00 ` Juergen Gross
2015-06-11 16:07 ` Ian Jackson
2015-06-11 16:42 ` Ian Jackson
2015-06-12 7:39 ` Chun Yan Liu
2015-06-12 8:06 ` Chun Yan Liu
2015-06-12 11:22 ` Ian Jackson
2015-06-15 14:17 ` George Dunlap
2015-06-15 14:25 ` Jürgen Groß
2015-06-15 14:34 ` George Dunlap
2015-06-15 18:26 ` Juergen Gross
2015-06-16 10:30 ` George Dunlap
2015-06-16 10:51 ` Juergen Gross
2015-06-16 11:11 ` George Dunlap
2015-06-16 11:19 ` Juergen Gross
2015-06-16 11:23 ` George Dunlap
2015-06-16 11:44 ` Ian Jackson
2015-06-17 11:24 ` Ian Campbell
2015-06-18 11:50 ` George Dunlap
2015-06-18 12:08 ` George Dunlap
2015-06-18 13:03 ` Juergen Gross [this message]
2015-06-22 13:29 ` Proposed plan for libxl USB interface (was Re: [PATCH V4 3/7] libxl: add pvusb API) George Dunlap
2015-06-22 14:14 ` Juergen Gross
2015-06-22 14:22 ` Ian Jackson
2015-06-23 2:42 ` Chun Yan Liu
2015-06-23 2:43 ` Chun Yan Liu
2015-06-23 2:44 ` Chun Yan Liu
2015-06-16 10:41 ` [PATCH V4 3/7] libxl: add pvusb API Ian Jackson
2015-06-16 10:56 ` Jürgen Groß
2015-06-16 11:03 ` George Dunlap
2015-06-16 11:10 ` Ian Jackson
2015-06-16 11:25 ` Juergen Gross
2015-06-16 11:45 ` George Dunlap
2015-06-16 12:02 ` Ian Jackson
2015-06-16 13:19 ` George Dunlap
2015-06-16 13:32 ` Juergen Gross
2015-06-16 13:37 ` [PATCH V4 3/7] libxl: add pvusb API [and 1 more messages] Ian Jackson
2015-06-16 14:41 ` George Dunlap
2015-06-16 15:58 ` Sander Eikelenboom
2015-06-16 15:59 ` Ian Jackson
2015-06-16 16:34 ` George Dunlap
2015-06-17 3:59 ` Juergen Gross
2015-06-17 10:27 ` George Dunlap
2015-06-18 6:24 ` Chun Yan Liu
2015-06-16 11:45 ` [PATCH V4 3/7] libxl: add pvusb API Ian Jackson
2015-06-16 13:06 ` Juergen Gross
2015-06-16 13:09 ` George Dunlap
2015-06-16 13:23 ` Juergen Gross
2015-06-16 13:29 ` George Dunlap
2015-06-16 13:49 ` Juergen Gross
2015-06-16 14:06 ` George Dunlap
2015-06-16 14:20 ` Juergen Gross
2015-06-16 14:37 ` George Dunlap
2015-06-17 11:34 ` Ian Campbell
2015-06-17 11:40 ` Juergen Gross
2015-06-18 6:20 ` Chun Yan Liu
2015-06-18 7:02 ` Juergen Gross
2015-06-18 8:50 ` Ian Campbell
2015-06-18 13:02 ` Juergen Gross
2015-06-16 15:38 ` George Dunlap
2015-06-16 11:01 ` George Dunlap
2015-06-16 11:12 ` Ian Jackson
2015-06-16 11:21 ` George Dunlap
2015-06-16 16:32 ` Ian Jackson
2015-06-16 16:39 ` George Dunlap
2015-06-16 16:51 ` Ross Philipson
2015-06-17 4:03 ` Jürgen Groß
2015-06-17 13:48 ` Ross Philipson
2015-06-15 17:47 ` George Dunlap
2015-06-23 10:18 ` Chun Yan Liu
2015-06-23 11:29 ` George Dunlap
2015-06-24 2:26 ` Chun Yan Liu
2015-06-10 3:20 ` [PATCH V4 4/7] libxl: add libxl_device_usb_assignable_list API Chunyan Liu
2015-06-10 3:20 ` [PATCH V4 5/7] xl: add pvusb commands Chunyan Liu
2015-06-12 7:37 ` Juergen Gross
2015-06-12 8:03 ` Chun Yan Liu
2015-06-12 8:22 ` Juergen Gross
2015-06-10 3:20 ` [PATCH V4 6/7] xl: add usb-assignable-list command Chunyan Liu
2015-06-10 3:20 ` [PATCH V4 7/7] domcreate: support pvusb in configuration file Chunyan Liu
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