On 06/16/2015 12:39 PM, George Dunlap wrote:
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
Is that an xHCI host controller? If so that might be how the system
represents the 2 logical (USB2/USB3) root hubs - each as its own
separate bus.
-George
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Ross Philipson
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