From: Andrey Borzenkov <arvidjaar@mail.ru>
To: Greg KH <greg@kroah.com>
Cc: jw schultz <jw@pegasys.ws>, linux-kernel@vger.kernel.org
Subject: Re: Does sysfs really provides persistent hardware path to devices?
Date: Sun, 31 Aug 2003 14:54:06 +0400 [thread overview]
Message-ID: <200308311453.00122.arvidjaar@mail.ru> (raw)
In-Reply-To: <20030818204218.GA3220@kroah.com>
On Tuesday 19 August 2003 00:42, Greg KH wrote:
> On Mon, Aug 18, 2003 at 10:21:22AM +0400, "Andrey Borzenkov" wrote:
> > just to show what I expected from sysfs - here is entry from Solaris
> > /devices:
> >
> > brw-r----- 1 root sys 32,240 Jan 24 2002
> > /devices/pci@16,4000/scsi@5,1/sd@0,0:a
> >
> > this entry identifies disk partition 0 on drive with SCSI ID 0, LUN 0
> > connected to bus 1 of controller in slot 5 of PCI bus identified
> > by 16. Now you can use whatever policy you like to give human
> > meaningful name to this entry. And if you have USB it will continue
> > further giving you exact topology starting from the root of your
> > device tree.
> >
> > and this path does not contain single logical id so it is not subject
> > to change if I add the same controller somewhere else.
> >
> > hopefully it clarifies what I mean ...
>
> Hm, a bit. First, have you looked at what sysfs provides? Here's one
> of my machines and tell me if it has all the info you are looking for:
>
> $ tree /sys/bus/scsi/
> /sys/bus/scsi/
>
> |-- devices
> | `-- 0:0:0:0 ->
> | ../../../devices/pci0000:00/0000:00:1e.0/0000:02:05.0/host0/0:0:0:0
^ ^unstable
[...]
>
> Now, from that you can see exactly where my scsi device is in the pci
> tree, and you can see in the block directory, what block device is
> assigned to what physical device in the device tree. Then there are 4
> partitions on this disk, all what those specific paramaters.
>
> So, when sda shows up, udev can determine that it lives on a specific
> scsi device, located in a specific place in the pci space, and that it
> has some number of partitions, all of specific sizes, wich specific
> major/minor numbers. It can then create all of the /dev links based on
> this.
>
> Please, take a few minutes looking at the existing sysfs tree on Linux.
> If you then have any specific questions, I would be glad to answer
> them.
>
Now I have to ask - do we discuss udev-0.2 (what I currently have) or
udev-as-it-can-be-in-fututure?
In udev-0.2 I cannot do it. I can say I want
TOPOLOGY, BUS="scsi", place="0.0.0.0", NAME="jaz"
but the next time I plug in SCSI card the host number changes. Even after I
unplug USB stick and plug it again it gets new host number.
And the same applies to USB, PCI and whatever. Sysfs exports entity numbers as
kernel enumerates them; while Solaris exports persistent device tree leaving
enumeration to user-level tools. Which means that if hardware changes for
whatever reason enumeration changes as well and your config becomes invalid.
> Hope this helps,
>
Well, we did not move a tiny bit since the beginning of this thread :) You
still did not show me namedev configuration that implements persistent name
for a device based on its physical location :)))
-andrey
next prev parent reply other threads:[~2003-08-31 10:54 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-08-18 6:21 "Andrey Borzenkov"
2003-08-18 20:42 ` your mail Greg KH
2003-08-31 10:54 ` Andrey Borzenkov [this message]
2003-09-24 21:18 ` Does sysfs really provides persistent hardware path to devices? Greg KH
2004-01-17 20:34 ` Andrey Borzenkov
2004-01-17 21:34 ` Greg KH
2004-01-19 13:08 ` Olaf Hering
2004-01-19 13:59 ` Andries Brouwer
2004-01-19 14:04 ` Olaf Hering
2004-03-14 11:53 ` Andrey Borzenkov
2004-03-14 19:25 ` Horst von Brand
-- strict thread matches above, loose matches on Subject: below --
2003-08-19 17:56 David Brownell
2003-07-26 16:36 Andrey Borzenkov
2003-07-26 16:43 ` Randy.Dunlap
2003-07-26 16:50 ` Greg KH
2003-07-28 16:44 ` Andrey Borzenkov
2003-07-28 17:03 ` Greg KH
2003-08-17 16:41 ` Andrey Borzenkov
2003-08-17 18:28 ` Greg KH
2003-08-18 2:04 ` jw schultz
2003-08-18 20:47 ` Greg KH
2003-07-26 16:54 ` OSDL
2003-07-26 16:59 ` J.C. Wren
2003-07-26 17:07 ` Greg KH
2003-07-26 22:51 ` Dax Kelson
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