[MODERATED] Re: [PATCH 4/4] walnut 4

On Thu, Mar 07, 2019 at 02:56:31PM +0100, speck for Greg KH wrote:
> sysfs files have the ability to be "shown" or not, on their own.  There
> is a "is_visable()" callback for every sysfs group.
> 
> This allows you to set a whole bunch of groups to a device, and then,
> when the device is created, the kobject core will call back to you and
> ask "should I show this file?"  At that point in time, you can do your
> check for "boot_cpu_has(...)" and the like to see if you really should
> be showing the file or not.
> 
> This saves you all the horrid mess of the merge_attr() function, trying
> to overload NULL pointers here in this attribute list, and other such
> hacks.
> 
> I guess no one stopped to think why _only_ the perf cpu code has a
> function like merge_attr(), and how the rest of the kernel could get
> away without needing a hack like that :(
> 
> Anyway, rant over.  I'll see if I can squeze this into the 4.9.y tree as
> it was before the major revamp of the perf cpu sysfs files.
> 
> In the future, someone should just switch all of this to attribute
> groups, like the rest of the kernel uses, so no such crazyness is
> needed.

Right; that would be a really nice cleanup. I suppose nobody who touched
all that (very much including me) knew about that is_visible() thing.

I'll try and not forget and make someone clean that up.