pattern matching in udev

pattern matching in udev

[Stephane Chauveau]

Hello,

did anyone considered the idea of using pattern matching in udev.

The current mecanism is nice but it requires an exact match. 

For example, I have a USB dual memory card reader which
produces 2 devices (such as /block/sda and /block/sdb). They
have the same characteristics (model, vendor,...). The only
difference is their bus 'id'  (N:0:0:0 and N:0:0:1 with N a scsi
host number). 

LABEL is useless because the 'keys' are identical and TOPOLOGY
is also not what I want because the scsi host are not constant.

The current solution is to use CALLOUT but a better way to do it
would be to add some simple pattern matching capabilities to udev.

For example using the usual * and ? :
 
LABEL, BUS="scsi", vendor="ImageMate CF-SM ", ID="*:0:0:0" ,  NAME="mem0-%n"
LABEL, BUS="scsi", vendor="ImageMate CF-SM ", ID="*:0:0:1" ,  NAME="mem1-%n"

Or even better using regular expressions that could be reused to build
the final name:

REGEXP "<$bus><$vendor><$id>"="<scsi><ImageMate.*><.*:0:0:\(.*\)>",
             NAME="mem\1-%n"

S. Chauveau






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Re: pattern matching in udev

[Patrick Mansfield]

On Sat, Nov 29, 2003 at 09:58:20PM +0100, Stephane Chauveau wrote:

> LABEL is useless because the 'keys' are identical and TOPOLOGY
> is also not what I want because the scsi host are not constant.
> 
> The current solution is to use CALLOUT but a better way to do it
> would be to add some simple pattern matching capabilities to udev.

Yes, that sounds like a good idea.

> For example using the usual * and ? :
>  
> LABEL, BUS="scsi", vendor="ImageMate CF-SM ", ID="*:0:0:0" ,  NAME="mem0-%n"
> LABEL, BUS="scsi", vendor="ImageMate CF-SM ", ID="*:0:0:1" ,  NAME="mem1-%n"

> Or even better using regular expressions that could be reused to build
> the final name:
> 
> REGEXP "<$bus><$vendor><$id>"="<scsi><ImageMate.*><.*:0:0:\(.*\)>",
>              NAME="mem\1-%n"

IMO the pattern matching should be part of the TOPOLOGY plus PLACE.

The scsi naming also requires a parent, your example above is only valid
if you have one host adapter connected (or one usb mass storage device
attached), there could exist another sd on *:0:0:0.

The matching should be capable of including the parent path, or more
easily but uglier, the whole sysfs path. 

For example:

Two usb mass storage at LUN 0 and LUN1:

/sysfs/devices/pci0000:00/0000:00:07.2/usb1/1-1/1-1:1.0/host0/0:0:0:0
/sysfs/devices/pci0000:00/0000:00:07.2/usb1/1-1/1-1:1.0/host0/0:0:0:1

And a system with a scsi host adapter with a single device at LUN 0:

/sysfs/devices/pci0000:01/0000:01:0c.0/host1/1:0:0:0

Could be named via:

TOPOLOGY, BUS="usb", place="pci0000:00/0000:00:07.2/usb1/1-1/1-1:1.0/*/*:0:0:0", NAME="mem0-%n"

TOPOLOGY, BUS="usb", place="pci0000:00/0000:00:07.2/usb1/1-1/1-1:1.0/*/*:0:0:1", NAME="mem1-%n"

TOPOLOGY, BUS="usb", place="pci0000:01/0000:01:0c.0/*/*:0:0:0" NAME="disk1%n"

-- Patrick Mansfield


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Re: pattern matching in udev

[Greg KH]

On Sat, Nov 29, 2003 at 09:58:20PM +0100, Stephane Chauveau wrote:
> The current solution is to use CALLOUT but a better way to do it
> would be to add some simple pattern matching capabilities to udev.
> 
> For example using the usual * and ? :
> 
> LABEL, BUS="scsi", vendor="ImageMate CF-SM ", ID="*:0:0:0" ,  NAME="mem0-%n"
> LABEL, BUS="scsi", vendor="ImageMate CF-SM ", ID="*:0:0:1" ,  NAME="mem1-%n"

Yes, using '*' in this manner would be nice to have.  Care to hack up
the strncmp_wildcard() function to achieve this?

> Or even better using regular expressions that could be reused to build
> the final name:
> 
> REGEXP "<$bus><$vendor><$id>"="<scsi><ImageMate.*><.*:0:0:\(.*\)>",
>             NAME="mem\1-%n"

Ick, if you want to do something like this, CALLOUT to a perl script :)

thanks,

greg k-h


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Re: pattern matching in udev

[Olaf Hering]

 On Wed, Dec 03, Patrick Mansfield wrote:

> On Wed, Dec 03, 2003 at 08:19:44PM +0100, Stephane Chauveau wrote:
> > > > REGEXP "<$bus><$vendor><$id>"="<scsi><ImageMate.*><.*:0:0:\(.*\)>",
> > > >              NAME="mem\1-%n"
> > >
> > > IMO the pattern matching should be part of the TOPOLOGY plus PLACE. 
> > >
> > > The scsi naming also requires a parent, your example above is only valid
> > > if you have one host adapter connected (or one usb mass storage device
> > > attached), there could exist another sd on *:0:0:0.
> > 
> > Not really because my example matches the $bus, the $id and the $vendor.
> 
> There could be another identical scsi device with the same id and vendor.
> 
> I thought the PCI sysfs id's were constant for a given hardware, but I'm
> told they can change with PCI hotplug, so the full sysfs path I mentioned
> previously will not be constant across boots with PCI hotplugging.

You cant have everything. How do you describe a filesystem to mount:
Its either the location, then the content may change, or it is the
content, then the location can change (content in the sense of fs UUID).

And in the case of pci cards, there is no need for PCI hotplug. Just
open your PC and move the SCSI card from slot a to slot b. result:
device node doesnt match if you go for location.


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

sUse lINUX ag, n√úRNBERG


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Re: pattern matching in udev

[Chauveau S.]

Patrick Mansfield wrote:

>On Wed, Dec 03, 2003 at 08:19:44PM +0100, Stephane Chauveau wrote:
>  
>
>>>>REGEXP "<$bus><$vendor><$id>"="<scsi><ImageMate.*><.*:0:0:\(.*\)>",
>>>>             NAME="mem\1-%n"
>>>>        
>>>>
>>>IMO the pattern matching should be part of the TOPOLOGY plus PLACE. 
>>>
>>>The scsi naming also requires a parent, your example above is only valid
>>>if you have one host adapter connected (or one usb mass storage device
>>>attached), there could exist another sd on *:0:0:0.
>>>      
>>>
>>Not really because my example matches the $bus, the $id and the $vendor.
>>    
>>
>
>There could be another identical scsi device with the same id and vendor.
>
>I thought the PCI sysfs id's were constant for a given hardware, but I'm
>told they can change with PCI hotplug, so the full sysfs path I mentioned
>previously will not be constant across boots with PCI hotplugging.
>  
>

I agree that matching  the vendor is not enough but this is because my 
example is incorrect.
What I call '$vendor' is my example is in fact the '$model'.
The 'ImageMate' is an external USB memory card reader so the PCI or the 
SCSI ids are
not constant and cannot be used at all (except the last bit to 
differenciate the 2 slots on the
card reader). The only way to identify a USB device is to match the 
'model' and the usb
device 'id'

Your remark about having identical devices is especially relevant in 
case of USB (or other
hot-plugable) devices. For example, how could udev handle 2 identical 
USB joysticks?
Ideally, udev should be able to create a device 'js0' for the 1st 
joystick plugged in, 'js1'
for the second, etc.
One accepatble way could be to use the USB topology! the joystick 
plugged in the nth
USB slot would be 'jsn' but that won't work with wireless devices.

>  
>
>>A single method capable of pattern matching on all the available informations 
>>could be used to replace all the methods currently in implemented in udev 
>>(except maybe REPLACE which has a different purpose). 
>>    
>>
>
>-- Patrick Mansfield
>
>  
>
Stephane Chauveau



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Re: pattern matching in udev

[Ihno Krumreich]

On Thu, Dec 04, 2003 at 10:51:32AM +0100, Olaf Hering wrote:
>  On Wed, Dec 03, Patrick Mansfield wrote:
> 
> > On Wed, Dec 03, 2003 at 08:19:44PM +0100, Stephane Chauveau wrote:
> > > > > REGEXP "<$bus><$vendor><$id>"="<scsi><ImageMate.*><.*:0:0:\(.*\)>",
> > > > >              NAME="mem\1-%n"
> > > >
> > > > IMO the pattern matching should be part of the TOPOLOGY plus PLACE. 
> > > >
> > > > The scsi naming also requires a parent, your example above is only valid
> > > > if you have one host adapter connected (or one usb mass storage device
> > > > attached), there could exist another sd on *:0:0:0.
> > > 
> > > Not really because my example matches the $bus, the $id and the $vendor.
> > 
> > There could be another identical scsi device with the same id and vendor.
> > 
> > I thought the PCI sysfs id's were constant for a given hardware, but I'm
> > told they can change with PCI hotplug, so the full sysfs path I mentioned
> > previously will not be constant across boots with PCI hotplugging.
> 
> You cant have everything. How do you describe a filesystem to mount:
> Its either the location, then the content may change, or it is the
> content, then the location can change (content in the sense of fs UUID).
> 
> And in the case of pci cards, there is no need for PCI hotplug. Just
> open your PC and move the SCSI card from slot a to slot b. result:
> device node doesnt match if you go for location.

I think the primary goal should be that adding and removing of
devices (or controllers) does not change the name of
the old/remaning devices.
If you open the PC and redistribute the PCI-Cards to the PCI-slots
you can expect that something changed.

Ihno

-- 
Best regards/Mit freundlichen Grüßen

Ihno Krumreich

"Never trust a computer you can lift."
--
Ihno Krumreich            ihno@suse.de
SuSE Linux AG             Projectmanager S390 & zSeries
Deutschherrnstr. 15-19    +49-911-74053-439
90429 Nürnberg            http://www.suse.de


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Re: pattern matching in udev

[Olaf Hering]

 On Thu, Dec 04, Ihno Krumreich wrote:

> If you open the PC and redistribute the PCI-Cards to the PCI-slots
> you can expect that something changed.

Again, if you cared about location, then you lost. If you had used the
fs UUID as example then everything would continue to work.

Its up to the admin to decide what is important. You cant have both at
the same time.

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

sUse lINUX ag, n√úRNBERG


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