Subject: Re: creating new ioctls
To: Bill Studenmund <>
From: Colin Wood <>
List: tech-kern
Date: 08/05/1997 12:51:27
Bill Studenmund wrote:

> > Am I right in assuming that so long as the starting letter (in this
> > case "I") is unique across the system, you can create whole new groups
> > of ioctls?
> > 
> > I ask since I'm starting to hack on the random device, and would like
> > to have a few ioctls to get snapshots of some data while debugging and
> > in production.
> Actually, I think it only needs to be unique among all the interveening
> steps the ioctl covers. If you have a tty device, you need to look out
> for the 't' ioctls (tty subsystem). Socket devices need to watch out
> for the socket family, etc.
> The difference is that, if you made a character device which didn't use
> the tty system, you could re-use the 't' ioctl's. It'd be sick &
> confusing, but it'd work.
> Also, there is a 'u' hierarchy which is dedicated to whatever the
> driver wants to do.

Would you mind explaining just exactly what you mean by this last


Colin Wood                       
Component Design Engineer - MD6                 Intel Corporation
I speak only on my own behalf, not for my employer.