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

[Greg KH <gregkh@linuxfoundation.org>]

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?

thanks,

greg k-h