Re: [PATCH] [PNP] 'modalias' sysfs export

[Adam Belay <ambx1@neo.rr.com>]

On Sat, Mar 11, 2006 at 05:38:47PM -0800, Andrew Morton wrote:
> Pierre Ossman <drzeus-list@drzeus.cx> wrote:
> >
> >  Here is a patch for doing multi line modalias for PNP devices. This will
> >  break udev, so that needs to be updated first.
> > 
> >  I had a longer look at the card part and it seems that module aliases
> >  cannot be reliably used for it. Not without restructuring the system at
> >  least. The possible combinations explode when you notice that the driver
> >  ids needs to be just at subset of the card, without any ordering.
> > 
> >  If I got my calculations right, a PNP card would have to have roughly
> >  2^(2n) aliases, where n is the number of device ids. So right now, I
> >  lean towards only adding modalias support for the non-card part of the
> >  PNP layer.
> > 
> >  Andrew, do you want a fix for the patch in -mm or can you remove the
> >  part of it that modifies drivers/pnp/card.c by yourself?
> 
> I assume you mean that the drivers/pnp/card.c patch of
> pnp-modalias-sysfs-export.patch needs to be removed and this patch applies
> on top of the result.
> 
> But I don't want to break udev.

I think supporting multiple IDs per node is a reasonable expectation to
have from udev (even for subsystems beyond PnP).  Kay, would this be
difficult to add?

However, I'm a little confused as to why we're exporting these "modalias"
strings from a kernel interface in the first place.  Wouldn't it be better
from an abstraction barrier standpoint to have userspace generate such
strings from information it gathered through bus-specific interfaces? As
can be seen from this example, when the modalias (or essentially a device
identification key) is imposed at the kernel level driver model interface,
one has to make policy decisions (e.g. what legacy features such as isapnp
are we going to only psuedo-support).

Thanks,
Adam
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