Re: ioctl(2) numbers

[Robert Swindells <rjs%fdy2.co.uk@localhost>]

Robert Elz <kre%munnari.OZ.AU@localhost> wrote:
>    Date:        Wed, 01 Aug 2018 10:56:28 +0100
>    From:        Robert Swindells <rjs%fdy2.co.uk@localhost>
>    Message-ID:  <x7sh3y2ywj.fsf%ren.fdy2.co.uk@localhost>
>
>  | Does it matter if ioctl(2) numbers overlap so long as they are in
>  | different groups ?
>
>To expand on thorpej's answer ... an "ioctl nulmber" is a 32 bit
>constant which we typically build from a character (8 bits) an
>integer (8 bits) and an argument size (13 bits), with 3 more bits
>of no-copy, copy-in, copy-out.
>
>If the 32 bit result is different from all others, all is fine. 

I understand how ioctl works.

I asked because it looked as if there was a convention within that file
that numbers be unique, even if they were in different groups.

Robert Swindells