Re: [PATCH 1/3] sysfs: Fix is_visible() support for binary attributes

[Guenter Roeck]

On 09/08/2015 08:58 PM, Greg KH wrote:
> On Tue, Sep 08, 2015 at 06:10:16PM -0700, Guenter Roeck wrote:
> > Hi Emilio,
> >
> > On 09/08/2015 05:51 PM, Emilio López wrote:
> > > Hi Greg & Guenter,
> > [ ... ]
> > > > > > Unless I am missing something, this is not explained anywhere, but it is
> > > > > > not entirely trivial to understand. I think it should be documented.
> > >
> > > I agree. I couldn't find any mention of what this int was supposed to be by looking at Documentation/ (is_visible is not even mentioned :/) or include/linux/sysfs.h. Once we settle on something I'll document it before sending a v2.
> > In the include file ? No strong preference, though.
> >
> > > By the way, I wrote a quick coccinelle script to match is_visible() users which reference the index (included below), and it found references to drivers which do not seem to use any binary attributes, so I believe changing the index meaning shouldn't be an issue.
> > Good.
> >
> > > > > I agree, make i the number of the bin attribute and that should solve
> > > > > this issue.
> > > > No, that would conflict with the "normal" use of is_visible for non-binary
> > > > attributes, and make the index all but useless, since the is_visible function
> > > > would have to search through all the attributes anyway to figure out which one
> > > > is being checked.
> > >
> > > Yeah, using the same indexes would be somewhat pointless, although not many seem to be using it anyway (only 14 files matched). Others seem to be comparing the attr* instead. An alternative would be to use negative indexes for binary attributes and positive indexes for normal attributes.
> > ... and I probably wrote or reviewed a significant percentage of those ;-).
> >
> > Using negative numbers for binary attributes is an interesting idea.
> > Kind of unusual, though. Greg, any thoughts on that ?
>
> Ick, no, that's a mess, maybe we just could drop the index alltogether?

No, please don't. Having to manually compare dozens of index pointers would be
even more of a mess.

Guenter


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