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From: Kay Sievers <kay.sievers@vrfy.org>
To: linux-hotplug@vger.kernel.org
Subject: Re: udev enhancements
Date: Thu, 16 Dec 2004 21:55:02 +0000	[thread overview]
Message-ID: <1103234102.14134.170.camel@localhost.localdomain> (raw)
In-Reply-To: <41C1551F.6060601@suse.de>

On Thu, 2004-12-16 at 10:27 +0100, Hannes Reinecke wrote:
> I'm trying to figure out the best way to incorporating udev into some 
> system tools. Currently we're facing the following problem:
> 
> Any program dealing with device nodes (e.g. parted) need to figure out 
> some information about the device it handles:
> - partition naming: given a device name, generate the name of a
>    partition on that device.
> - number of partitions: each block device type has it's own maximal
>    number of partitions.
> 
> These information is mostly gathered from the device name. Of course, 
> you can't do that if you're using udev.

Why? You still know the sysfs path with the kernel device name in it.

> So, to retain the existing functionality we would need to add two major 
> improvements to udev:
> 
> - Build udevinfo as library. This way any program can just link to this 
> library and retrieve any information from there instead of rely on some 
> build-in logic. That should actually be quite simple ...

Why do you want to link against it? What's the problem with executing
it, which is much easier to maintain?

> - Add a 'dry-run' logic to udev/udevinfo: Given a devicename, how would 
> a partition on that device be named?

> The latter is the _really_ hard part. Currently there is no relationship 
> in udev between a device and the partitions associated to that device.
> I would love to see that, though, as it would simplify the rules and the 
> run-time behaviour of udev significantly.
> With the current setup we have to re-run any program fetching 
> information about the device (e.g. scsi_id) every time a new partition 
> has been detected. If we had a device->partition relationship, we could 
> re-use the information from the device and just paste the 
> partition-specific bits to the end.

You may just use a PROGRAM script on the partitions rule, that returns
the node name of the main block device.

Kay



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  parent reply	other threads:[~2004-12-16 21:55 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2004-12-16  9:27 udev enhancements Hannes Reinecke
2004-12-16 14:41 ` Harald Hoyer
2004-12-16 14:48 ` Olaf Hering
2004-12-16 21:55 ` Kay Sievers [this message]
2004-12-21 16:59 ` Greg KH

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