Re: udev and the kernel's idea of a device

[Daniel Stekloff <dsteklof@us.ibm.com>]

On Tuesday 06 April 2004 02:06 pm, Greg KH wrote:
> On Tue, Apr 06, 2004 at 04:49:24PM -0400, Bill Nottingham wrote:
> > > > > As it is very simple
> > > > > to translate from the kernel device name to the real /dev name at
> > > > > any point in time using udevinfo, why is that not sufficient?
> > > >
> > > > Requires integrating udevinfo into various random userland apps...
> > > > it's certainly doable, but it just doesn't seem very clean.
> > >
> > > I agree, but what random userland apps are you talking about?
> >
> > Off the top of my head, iostat, cdrom capability checkers, fbset
> > and friends, etc. But, in the long run, see below.
>
> But those apps want to know the /dev node, right?  They don't get errors
> back from the kernel with the kernel device name (well, I don't know
> what iostat uses, but I think the later version use sysfs...).  Things
> like fbset want to know where the fb device is at in /dev, not the other
> way around.
>
> Or am I confused too?
>
> > > Can you think of a cleaner suggestion?
> >
> > Drill HAL throughout the entire OS. :)
>
> Yeah, that's the "correct" solution, but until then I imagine you need
> to get real work done :)


Our error log analysis application takes the information prefixed to an error 
message by dev_printk() macros and uses it as a key to query specific device 
information. We are using Martin Schwenke's lsvpd package to get all the 
Vital Product Data (VPD) about a device. His package currently builds a db of 
system devices, pulling information from various places like sysfs and 
sg3_utils, and provides commands for retrieving that information. 

We are working with Martin to increase the usability of lsvpd and its device 
database. Martin plans to hook lsvpd up to hotplug events for adding and 
removing devices. He also plans to store device name information for those 
devices named by udev. Finally, we plan to help him create an API for 
querying device information so we have *one* place to go for getting a 
device's vital data. 

I had originally thought an API would be needed for udev, but it can be done 
outside udev. Udev is for naming certain devices. What we need is an API for 
retrieving information from *all* system devices. 

For more information:

Error Log Analysis: http://evlog.sourceforge.net/ela.html

lsvpd: http://linux-diag.sourceforge.net/Lsvpd.html

Thanks,

Dan


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