In article <17583.2981.613185.784283@srapc2586.sra.co.jp>,
SODA Noriyuki  <soda@sra.co.jp> wrote:
>>>>>> On Fri, 7 Jul 2006 18:05:34 -0700,
>      Jason Thorpe <thorpej@shagadelic.org> said:
>
>>> this is false.  we have added more info to several sysctl's that
>>> could have been ioctl's and it did not require versioning the
>>> interface.  see KERN_PROC2.
>
>> I was pretty much speaking about ioctls.
>
>How ioctls differ from sysctl?
>It's just same with sysctl from this point of view.
>i.e. You can just assign different ioctl number.

The ioctl number has the size encoded in the ioctl. In sysctl it is separate.
So if you change the struct size in an ioctl, the ioctl number will change.
In the sysctl case, the size is passed in separately.

christos