Re: Does sysfs really provides persistent hardware path to devices?

Re: Does sysfs really provides persistent hardware path to devices?

[Andrey Borzenkov]

On Thursday 25 September 2003 01:18, Greg KH wrote:
> On Sun, Aug 31, 2003 at 02:54:06PM +0400, Andrey Borzenkov wrote:
> > 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
>
> Heh, so are the pci ids in that link too :)
>

I am not sure if you are just making fun here. No, in _this_ link pci ids are 
not unstable because I do not have hotpug PCI. But SCSI hosts are unstable:

{pts/0}% LC_ALL=C ll /sys/class/scsi_host/*/device
lrwxrwxrwx    1 root     root           71 Jan 17 22:59 
/sys/class/scsi_host/host7/device -> 
../../../devices/pci0000:00/0000:00:1f.4/usb2/2-2/2-2.4/2-2.4:1.0/host7/
lrwxrwxrwx    1 root     root           29 Jan 17 23:19 
/sys/class/scsi_host/host8/device -> ../../../devices/legacy/host8/

after unplugging and replugging USB stick:

pts/0}% LC_ALL=C ll /sys/class/scsi_host/*/device
lrwxrwxrwx    1 root     root           29 Jan 17 23:19 
/sys/class/scsi_host/host8/device -> ../../../devices/legacy/host8/
lrwxrwxrwx    1 root     root           71 Jan 17 23:25 
/sys/class/scsi_host/host9/device -> 
../../../devices/pci0000:00/0000:00:1f.4/usb2/2-2/2-2.4/2-2.4:1.0/host9/

host7 became host9

[... skipped as obsolete now...]
>
> And yes, we should add wild card matching for topology rules, it's on
> the todo list, I haven't had much time to work on udev lately.
>
> > > 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 :)))
>
> Ok, do you have any other ideas of how to do this?
>

given current sysfs implementation - using wildcards remains the only 
solution. I for now am using this trivial script:

pts/0}% cat /etc/udev/scripts/removables
#!/usr/bin/perl

my $devpath, $base;

$base = $1 if ($ARGV[0] =~ /(.*\D)\d*$/);
$devpath = readlink "/sys/block/$base/device";

if ($devpath =~ 
m|/devices/pci0000:00/0000:00:1f.4/usb2/2-2/2-2.4/2-2.4:1.0/host\d+/\d+:0:0:0|) 
{
        print "flash0";
} elsif ($devpath =~ 
m|/devices/pci0000:00/0000:00:1f.4/usb2/2-2/2-2.1/2-2.1:1.0/host\d+/\d+:0:0:0|) 
{
        print "flash1";
} elsif ($devpath =~ m|/devices/legacy/host\d+/\d+:0:4:0|) {
        print "jaz";
} else {
        exit(1);
}

1;

with config

KERNEL="sd*" PROGRAM="/etc/udev/scripts/removables %k" SYMLINK="%c/%D"

> And patches for udev are always welcome :)
>

as example shows it probably can be done without serious patches. The only 
problem is to make devpath available; at this point udev already computed it. 
If you think it makes sense, patch will follow.

regards

-andrey



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Re: Does sysfs really provides persistent hardware path to devices?

[Greg KH]

On Sat, Jan 17, 2004 at 11:34:13PM +0300, Andrey Borzenkov wrote:
> On Thursday 25 September 2003 01:18, Greg KH wrote:

Heh, nothing like a long time between responses :)

> > On Sun, Aug 31, 2003 at 02:54:06PM +0400, Andrey Borzenkov wrote:
> > > 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
> >
> > Heh, so are the pci ids in that link too :)
> >
> 
> I am not sure if you are just making fun here. No, in _this_ link pci ids are 
> not unstable because I do not have hotpug PCI.

Your PCI ids could change over reboots for a number of different
reasons (bios changes, adding or removing cards, phase of the moon,
etc.)  My point is, PCI ids can not be guananteed to be stable for
everyone.

> But SCSI hosts are unstable:

Exactly.

> given current sysfs implementation - using wildcards remains the only 
> solution. I for now am using this trivial script:

You know that udev now supports wildcards in its pattern matching,
right?

> pts/0}% cat /etc/udev/scripts/removables
> #!/usr/bin/perl
> 
> my $devpath, $base;
> 
> $base = $1 if ($ARGV[0] =~ /(.*\D)\d*$/);
> $devpath = readlink "/sys/block/$base/device";
> 
> if ($devpath =~ 
> m|/devices/pci0000:00/0000:00:1f.4/usb2/2-2/2-2.4/2-2.4:1.0/host\d+/\d+:0:0:0|) 
> {
>         print "flash0";

ick, isn't there a unique sysfs id in this location for this device that
you can query off of?  model?  vendor?  scsi uuid?

> } elsif ($devpath =~ 
> m|/devices/pci0000:00/0000:00:1f.4/usb2/2-2/2-2.1/2-2.1:1.0/host\d+/\d+:0:0:0|) 
> {
>         print "flash1";
> } elsif ($devpath =~ m|/devices/legacy/host\d+/\d+:0:4:0|) {
>         print "jaz";
> } else {
>         exit(1);
> }
> 
> 1;
> 
> with config
> 
> KERNEL="sd*" PROGRAM="/etc/udev/scripts/removables %k" SYMLINK="%c/%D"

I just removed %D from udev too :)

> > And patches for udev are always welcome :)
> >
> 
> as example shows it probably can be done without serious patches. The only 
> problem is to make devpath available; at this point udev already computed it. 
> If you think it makes sense, patch will follow.

I could see making devpath available as a % modifier.

thanks,

greg k-h


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Re: Does sysfs really provides persistent hardware path to devices?

[Kay Sievers]

On Sat, Jan 17, 2004 at 01:34:16PM -0800, Greg KH wrote:
> On Sat, Jan 17, 2004 at 11:34:13PM +0300, Andrey Borzenkov wrote:
> > as example shows it probably can be done without serious patches. The only 
> > problem is to make devpath available; at this point udev already computed it. 
> > If you think it makes sense, patch will follow.
> 
> I could see making devpath available as a % modifier.

It's available in the environment. PROGRAM="/bin/sh -c set>/tmp/set" shows:

  ACTION­d
  DEVPATH=/class/video4linux/video0
  DIRSTACK=()
  EUID=0
  GROUPS=()
  HOME=/
  ...


thanks,
Kay


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Re: Does sysfs really provides persistent hardware path to devices?

[Kay Sievers]

On Sun, Jan 18, 2004 at 02:03:12AM +0100, Kay Sievers wrote:
> On Sat, Jan 17, 2004 at 01:34:16PM -0800, Greg KH wrote:
> > On Sat, Jan 17, 2004 at 11:34:13PM +0300, Andrey Borzenkov wrote:
> > > as example shows it probably can be done without serious patches. The only 
> > > problem is to make devpath available; at this point udev already computed it. 
> > > If you think it makes sense, patch will follow.
> > 
> > I could see making devpath available as a % modifier.
> 
> It's available in the environment. PROGRAM="/bin/sh -c set>/tmp/set" shows:
> 
>   ACTION­d
>   DEVPATH=/class/video4linux/video0
>   DIRSTACK=()
>   EUID=0
>   GROUPS=()
>   HOME=/
>   ...

Oh, sorry, better to read the whole text :)
You mean the "device" path, right?

Kay


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Re: Does sysfs really provides persistent hardware path to devices?

[Olaf Hering]

 On Sat, Jan 17, Andrey Borzenkov wrote:

> > > 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 :)))
> >
> > Ok, do you have any other ideas of how to do this?
> >
> 
> given current sysfs implementation - using wildcards remains the only 
> solution. I for now am using this trivial script:
> 
> pts/0}% cat /etc/udev/scripts/removables
> #!/usr/bin/perl
> 
> my $devpath, $base;
> 
> $base = $1 if ($ARGV[0] =~ /(.*\D)\d*$/);
> $devpath = readlink "/sys/block/$base/device";
> 
> if ($devpath =~ 
> m|/devices/pci0000:00/0000:00:1f.4/usb2/2-2/2-2.4/2-2.4:1.0/host\d+/\d+:0:0:0|) 
> {
>         print "flash0";
> } elsif ($devpath =~ 
> m|/devices/pci0000:00/0000:00:1f.4/usb2/2-2/2-2.1/2-2.1:1.0/host\d+/\d+:0:0:0|) 
> {
>         print "flash1";
> } elsif ($devpath =~ m|/devices/legacy/host\d+/\d+:0:4:0|) {
>         print "jaz";
> } else {
>         exit(1);
> }

I'm not sure what you are trying to do. Working with the 'physical
location' of removeable devices will probably fail. The usb-storage
devices here have a serial field, I really hope it is unique, use it.

-- 
USB is for mice, FireWire is for men!

sUse lINUX ag, n√úRNBERG


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Re: Does sysfs really provides persistent hardware path to devices?

[Andries Brouwer]

On Mon, Jan 19, 2004 at 02:08:17PM +0100, Olaf Hering wrote:

> ... Working with the 'physical
> location' of removeable devices will probably fail. The usb-storage
> devices here have a serial field, I really hope it is unique, use it.

Too optimistic.
I have several devices with serial number 0.



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Re: Does sysfs really provides persistent hardware path to devices?

[Olaf Hering]

 On Mon, Jan 19, Andries Brouwer wrote:

> On Mon, Jan 19, 2004 at 02:08:17PM +0100, Olaf Hering wrote:
> 
> > ... Working with the 'physical
> > location' of removeable devices will probably fail. The usb-storage
> > devices here have a serial field, I really hope it is unique, use it.
> 
> Too optimistic.
> I have several devices with serial number 0.

Nice... Is 'serial' empty, or does it just have '0' in it? And would it
also fail to use vendor/device id for these beasts?

-- 
USB is for mice, FireWire is for men!

sUse lINUX ag, n√úRNBERG


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Re: Does sysfs really provides persistent hardware path to devices?

[Greg KH]

On Sun, Jan 18, 2004 at 03:05:18PM +0100, Kay Sievers wrote:
> On Sun, Jan 18, 2004 at 02:03:12AM +0100, Kay Sievers wrote:
> > On Sat, Jan 17, 2004 at 01:34:16PM -0800, Greg KH wrote:
> > > On Sat, Jan 17, 2004 at 11:34:13PM +0300, Andrey Borzenkov wrote:
> > > > as example shows it probably can be done without serious patches. The only 
> > > > problem is to make devpath available; at this point udev already computed it. 
> > > > If you think it makes sense, patch will follow.
> > > 
> > > I could see making devpath available as a % modifier.
> > 
> > It's available in the environment. PROGRAM="/bin/sh -c set>/tmp/set" shows:
> > 
> >   ACTION­d
> >   DEVPATH=/class/video4linux/video0
> >   DIRSTACK=()
> >   EUID=0
> >   GROUPS=()
> >   HOME=/
> >   ...
> 
> Oh, sorry, better to read the whole text :)
> You mean the "device" path, right?

No, I think he wanted DEVPATH, or that's what I thought he ment...

thanks,

greg k-h


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Re: Does sysfs really provides persistent hardware path to devices?

[Andrey Borzenkov]

On Monday 19 January 2004 16:08, Olaf Hering wrote:
>  On Sat, Jan 17, Andrey Borzenkov wrote:
> > > > 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 :)))
> > >
> > > Ok, do you have any other ideas of how to do this?
> >
> > given current sysfs implementation - using wildcards remains the only
> > solution. I for now am using this trivial script:
> >
> > pts/0}% cat /etc/udev/scripts/removables
> > #!/usr/bin/perl
> >
> > my $devpath, $base;
> >
> > $base = $1 if ($ARGV[0] =~ /(.*\D)\d*$/);
> > $devpath = readlink "/sys/block/$base/device";
> >
> > if ($devpath =~
> > m|/devices/pci0000:00/0000:00:1f.4/usb2/2-2/2-2.4/2-2.4:1.0/host\d+/\d+:0
> >:0:0|) {
> >         print "flash0";
> > } elsif ($devpath =~
> > m|/devices/pci0000:00/0000:00:1f.4/usb2/2-2/2-2.1/2-2.1:1.0/host\d+/\d+:0
> >:0:0|) {
> >         print "flash1";
> > } elsif ($devpath =~ m|/devices/legacy/host\d+/\d+:0:4:0|) {
> >         print "jaz";
> > } else {
> >         exit(1);
> > }
>
> I'm not sure what you are trying to do.

I am trying to assign name for a USB slot on my PCs front so that when I plug 
in USB stick or USB drive or whatever I get the same name. Always.

> Working with the 'physical 
> location' of removeable devices will probably fail.

why? The 'physical location' is the only thing that is unlikely to change 
unless you physically change you hardware.

Anyway - it appears that udev (as of 022 now) still does not support doing it. 
Once more - I want to make sure that SCSI disk plugged in specific USB slot 
(that does not ever change) always gets the same name. So that I always know 
how to access it.

naive user would think that something like

KERNEL="sd*" BUS="usb" PLACE="2.4:1.0" SYMLINK="flash0/sd%n"

would work. Surely it does not. When udev sees "sd*" it does not see bus USB. 
When udev sees bus USB it does not see "sd*". It does (probably) see sd* on 
bus SCSI but it does not help me in any way because I have no way to 
associate SCSI ID with USB port. While kernel does know that "sda" is a child 
of USB port 2.4:0.1 I do not see any way to express it in udev.

Could somebody explain what am I doing wrong. Thank you. 

> The usb-storage 
> devices here have a serial field, I really hope it is unique, use it.

Sigh ... let me quote:

> I have 6 different firewire hard drives, and an iPod, a usb stick, a usb
> stick/camera combo, and a bunch of flash memory products (CF, SM, SD) so
> such a thing would be incredibly useful to me.  I'm always modifying my
> fstab to keep things in order.

so you suggest him to add every device separately? And if he has half a dozen 
friends having half a dozen devices each - do you suggest adding yet another 
40 lines for all of them? And keep it in sync with all updates and upgrades?

On the contrary he likely has just a couple of USB ports and one firewire and 
he just needs three lines for *any* device which is ever going to be plugged 
in. Or he would need if it was supported.

thank you

-andrey


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Re: Does sysfs really provides persistent hardware path to devices?

[Horst von Brand]

Andrey Borzenkov <arvidjaar@mail.ru> said:

[...]

> I am trying to assign name for a USB slot on my PCs front so that when I
> plug in USB stick or USB drive or whatever I get the same name. Always.

Not necessary: You can mount by volume label, or UUID (Yes, need a sane
filesystem for that... and MS-DOS ones aren't. Sorry.)

Dangerous: You plug a _different_ USB stick in, and think it is the same.

Besides, plugging your drive in "the same place" on USB is useful today,
with 1 or 2 conectors. Add hubs, and you are talking about hundreds of
places... better concentrate on getting the machine keep track of
bureaucratic details.
-- 
Dr. Horst H. von Brand                   User #22616 counter.li.org
Departamento de Informatica                     Fono: +56 32 654431
Universidad Tecnica Federico Santa Maria              +56 32 654239
Casilla 110-V, Valparaiso, Chile                Fax:  +56 32 797513


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