From mboxrd@z Thu Jan 1 00:00:00 1970 From: George Dunlap Subject: Re: [PATCH V4 3/7] libxl: add pvusb API Date: Tue, 16 Jun 2015 17:39:03 +0100 Message-ID: <55805127.1010105@eu.citrix.com> References: <1433906441-3280-1-git-send-email-cyliu@suse.com> <1433906441-3280-4-git-send-email-cyliu@suse.com> <21887.64856.265751.921367@mariner.uk.xensource.com> <21888.1191.40486.530231@mariner.uk.xensource.com> <21888.20366.133089.128189@mariner.uk.xensource.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <21888.20366.133089.128189@mariner.uk.xensource.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Ian Jackson Cc: Wei Liu , Ian Campbell , Chunyan Liu , "xen-devel@lists.xen.org" , Jim Fehlig , Simon Cao List-Id: xen-devel@lists.xenproject.org On 06/16/2015 05:32 PM, Ian Jackson wrote: > I have just discovered that the value used in /dev/disk/by-path is not > from sysfs, or at least, not directly. > > udev cobbles it together with a bunch of string mangling, from > information mostly from sysfs. There is no corresponding thing for > usb devices. > > So Linux, the kernel, does not actually provide a stable device name > string. This is obviously absurd, but I think fixing it is out of > scope. > > I suggest we provide a facility to allow a user to specify a fnmatch > glob pattern to be applied to the sysfs path. That way when they see > their device is > /devices/pci0000:00/0000:00:1d.7/usb1/1-1 > they can write > /devices/pci0000:00/0000:00:1d.7/usb*/*-1 > which will match exactly and only the right thing. What about Juergen's system that has two usbN directories in a single pci node? Quoting: --- Hmm, perhaps. On my system I've got: /sys/devices/pci0000:00/0000:00:14.0/usb3/ /sys/devices/pci0000:00/0000:00:14.0/usb4/ So two busses on one pci bus address. Are usb3 and usb4 always in this order or are they sometimes just numbered the other way round? --- Assuming that usb3 and usb4 are actually distinct busses, and they might both have something plugged into port; in which case a glob like this: devices/pci0000:00/0000:00:14.0/usb*/*-1 Might match both of the following: /sys/devices/pci0000:00/0000:00:14.0/usb3/3-1 /sys/devices/pci0000:00/0000:00:14.0/usb4/4-1 -George