From: Ian Jackson <Ian.Jackson@eu.citrix.com>
To: George Dunlap <George.Dunlap@eu.citrix.com>
Cc: "Jürgen Groß" <jgross@suse.com>, "Wei Liu" <wei.liu2@citrix.com>,
"Ian Campbell" <ian.campbell@citrix.com>,
"Ian Jackson" <Ian.Jackson@eu.citrix.com>,
"Chunyan Liu" <cyliu@suse.com>,
"xen-devel@lists.xen.org" <xen-devel@lists.xen.org>,
"Jim Fehlig" <jfehlig@suse.com>,
"Simon Cao" <caobosimon@gmail.com>
Subject: Re: [PATCH V4 3/7] libxl: add pvusb API [and 1 more messages]
Date: Tue, 16 Jun 2015 14:37:50 +0100 [thread overview]
Message-ID: <21888.9902.709503.386019@mariner.uk.xensource.com> (raw)
In-Reply-To: <21888.1058.681450.470806@mariner.uk.xensource.com>, <CAFLBxZbnN3KnH3vYmsBTJoKRuF=V7QheCnoDbxmafwHwgMnM3A@mail.gmail.com>
George Dunlap writes ("Re: [Xen-devel] [PATCH V4 3/7] libxl: add pvusb API"):
> Remember that the path you gave in your previous e-mail isn't the path
> for the *usb device*, it's the path for the *block device*. It
> contains a PCI address, but it looks like it also contains part of the
> USB topology. Are you sure that's actually a stable interface, or
> does it just happen that on your hardware the discovery always happens
> in the same order?
The block device is (in path terms) underneath the usb device,
obviously. Not all of that path is relevant to identifying the
USB device.
> On my system /sys/bus/usb/devices/2-3.3 is a link to
> /sys/devices/pci0000:00/0000:00:1d.7/usb2/2-3/2-3.3/. This contains
> the pci bus address, but it also contains the bus number, which we've
> just said may be unstable across reboots.
You mean the 2 in `usb2' ? I think that bus number is the bus number
within the controller, not globally.
> I suppose it might be possible to specify <buspci,port> -- the pci
> address of the root bus, and the topology from there. In theory I
> guess that should be stable?
Yes. The whole point of paths like this is that they are stable if
the physical topology doesn't change. So on my netbook
/dev/disk/by-path/pci-0000:00:1d.7-usb-0:1:1.0-scsi-0:0:0:0-part1
always refers to the 1st MBR partition on logical device 0 on the USB
storage device plugged into the USB port physically on the front left
of the computer.
> In any case, at the moment you're essentially inventing from whole
> cloth a new way of specifying USB devices that (as far as I know)
> isn't supported by any other program that uses USB.
If you can't specify the device by hardware path, you can't specify it
deterministically.
And as you can see it _is_ supported by other programs that use USB.
"mount" can use it!
I think the hardware path to the controller, at least, should be
treated as an opaque OS-specific string. It might have a different
format on BSD.
Ian.
next prev parent reply other threads:[~2015-06-16 13:37 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
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 ` Ian Jackson [this message]
2015-06-16 14:41 ` [PATCH V4 3/7] libxl: add pvusb API [and 1 more messages] 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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