Date: Tue, 22 May 2007 10:38:57 +0200
From: Cornelia Huck <cornelia.huck@de.ibm.com>
To: Kay Sievers <kay.sievers@vrfy.org>
Cc: Pierre Ossman <drzeus-list@drzeus.cx>, Greg KH <greg@kroah.com>,
       LKML <linux-kernel@vger.kernel.org>,
       Kristian =?ISO-8859-15?Q?H=F8gsberg?= <krh@bitplanet.net>
Subject: Re: Race free attributes in sysfs
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On Mon, 21 May 2007 21:28:15 +0200,
Kay Sievers <kay.sievers@vrfy.org> wrote:

> We could change the driver-core to suppress the creation of an attribute
> if the attribute's show() or store() method returns something like
> -ENOENT at registration time?
> The driver would pass _all_ possible attributes of the device at
> registration time, but the core would only create the attributes which
> are implemented for this particular device? Would that work for you?
> 
> There are already subsystems who need to do similar things internally
> (firewire), and it may be nice to add such functionality to the core.

This sounds a bit hackish (overloading the meaning of the show() and
store() methods).

> You can assign any number of attribute groups to the device. If they
> don't have a group name, they will all be created directly at the device
> level. Would that work for you?

What about generic "conditional attribute groups"? Add a check() method
which is called just before adding them, and only add them if check()
returned 0 (or doesn't exist)?
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