From: George Dunlap <George.Dunlap@eu.citrix.com>
To: Ian Jackson <Ian.Jackson@eu.citrix.com>
Cc: "Jürgen Groß" <jgross@suse.com>, "Wei Liu" <wei.liu2@citrix.com>,
"Ian Campbell" <ian.campbell@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 17:34:21 +0100 [thread overview]
Message-ID: <CAFLBxZZ=6uQ_SGeJ1bGySv87MJGbj1qzb+++DDYGmga8iv7W8w@mail.gmail.com> (raw)
In-Reply-To: <21888.18408.443895.592922@mariner.uk.xensource.com>
On Tue, Jun 16, 2015 at 4:59 PM, Ian Jackson <Ian.Jackson@eu.citrix.com> wrote:
> George Dunlap writes ("Re: [Xen-devel] [PATCH V4 3/7] libxl: add pvusb API [and 1 more messages]"):
>> > 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.
>>
>> That would be great if it were true, but I'm not convinced that the
>> above path doesn't include a globally-enumerated bus number, which might
>> change across reboots if it's enumerated in a different order.
>>
>> It may be that the format above is *not* based on the sysfs path of the
>> device; that the '0' immediately after the USB means "the first (and
>> perhaps only) controller at this PCI address". In which case, yes,
>> having a string like this might be a unique identifier for a particular
>> port that would be stable across reboots. That needs some investigation.
>
> That does seem to be the case:
What seems to be the case -- that it contains the global bus, or not?
> Looking at the output of udevadm monitor --property for sdc1 (on
> another plug):
>
> DEVPATH=/devices/pci0000:00/0000:00:1d.7/usb1/1-1/1-1:1.0/host22/target22:0:0/22:0:0:0/block/sdc/sdc1
> ID_PATH=pci-0000:00:1d.7-usb-0:1:1.0-scsi-0:0:0:0
> ID_PATH_TAG=pci-0000_00_1d_7-usb-0_1_1_0-scsi-0_0_0_0
>
> I don't know where that ID_PATH comes from.
It looks like that's constructed in udev:
http://cgit.freedesktop.org/systemd/systemd/tree/src/udev/udev-builtin-path_id.c
See handle_usb() (line 542) in particular.
If I'm reading it right, what it basically does it take the
[bus]-[port], and replace it with usb-0:[port]. (IOW, the '0' is
hard-coded.)
Also, if I'm reading it right, this won't work properly for Juergen's
system that has two USB devices at the same pci address -- they'll
both end up resolving to [pciaddr]-usb-0:[whatever].
Juergen -- can you give this a try? Run "udevadm info" on the two USB
busses that share the same PCI slot, and see if the ID_PATH is the
same for both?
-George
next prev parent reply other threads:[~2015-06-16 16:34 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 ` [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 [this message]
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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