ioctl number change / backwards compatibility doubt

Greg KH greg at
Sun Jan 23 06:04:48 EST 2022

On Sun, Jan 23, 2022 at 08:55:30PM +1300, Paulo Miguel Almeida wrote:
> > > 1: Given the driver's history and ioctl number conflit, is the backwards
> > > compatibility something to be kept or not to be taken into consideration
> > > as ioctl numbering rules weren't followed?
> > 
> > Try to find out who is using these ioctls.  If you can change the
> > userspace tool at the same time, all is fine.  If not, then there can be
> > problems.
> Apologies for the delay, I had emailed the original author and I was waiting 
> for his reply before I could answer this. It turns out I haven't gotten
> an official answer from him yet. (I do understand that he might be busy)
> I googled a fair bit of time and I'm 99% confident that there isn't such
> userspace/lib tool so I guess this will have done the hard way :(

If there is no tool, why was the ioctl code written at all?  Something
had to call it.

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