Subject: Re: [PATCH 34/54] Driver Core: add kobj_attribute handling
From: Kay Sievers <kay.sievers@vrfy.org>
To: Greg KH <gregkh@suse.de>
Cc: Cornelia Huck <cornelia.huck@de.ibm.com>, linux-kernel@vger.kernel.org
In-Reply-To: <20071105171133.GD12843@suse.de>
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Date: Mon, 05 Nov 2007 18:25:40 +0100
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On Mon, 2007-11-05 at 09:11 -0800, Greg KH wrote:
> On Mon, Nov 05, 2007 at 05:23:32PM +0100, Kay Sievers wrote:
> > On Mon, 2007-11-05 at 13:42 +0100, Cornelia Huck wrote:
> > > On Fri,  2 Nov 2007 16:59:12 -0700,
> > > Greg Kroah-Hartman <gregkh@suse.de> wrote:
> > > 
> > > > From: Kay Sievers <kay.sievers@vrfy.org>
> > > > 
> > > > Add kobj_sysfs_ops to replace subsys_sysfs_ops. There is no
> > > > need for special kset operations, we want to be able to use
> > > > simple attribute operations at any kobject, not only ksets.
> > > > 
> > > > The whole concept of any default sysfs attribute operations
> > > > will go away with the upcoming removal of subsys_sysfs_ops.
> > > > 
> > > > Signed-off-by: Kay Sievers <kay.sievers@vrfy.org>
> > > > Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
> > > > ---
> > > >  include/linux/kobject.h |   10 ++++++++++
> > > >  lib/kobject.c           |   29 +++++++++++++++++++++++++++++
> > > >  2 files changed, 39 insertions(+), 0 deletions(-)
> > > 
> > > How about adding some simple wrappers around the new kobj_attribute
> > > structure? This makes the layering clearer.
> > 
> > > +#define KOBJ_ATTR(_name,_mode,_show,_store)		\
> > > +	struct kobj_attribute kobj_attr_##_name =	\
> > > +		__ATTR(_name,_mode,_show,_store)
> > 
> > That sounds fine.
> > 
> > > +extern int __must_check kobject_create_file(struct kobject *,
> > > 
> > > 					    struct kobj_attribute *);
> > > +extern void kobject_remove_file(struct kobject *,struct kobj_attribute *);
> > 
> > That should usually be done by default attributes assigned to the ktype.
> > Do you have a good use case, where people need to create such attributes
> > individually instead?
> 
> The s390 code that was converted to use kobj_attributes :)
> 
> These look very useful, I'll go add them to the series unless Kay really
> objects.

I just want to hear a good reason to create attributes individually. :)
Especially in conjunction with kobject_register(), these attributes are
not available at uevent time, which is really really bad.

Default attributes just work fine, and have the proper error handling
built-in. Offering special functions for it, may just encourage people
to continue this "broken" way of creating attributes.

So I really object, unless we get a good example why it's needed. :)

Kay

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