Subject: Re: Functional VOP_IOCTL
To: Bill Studenmund <>
From: Konrad Schroder <>
List: tech-kern
Date: 02/24/2003 18:19:18
On Mon, 24 Feb 2003, Bill Studenmund wrote:

> See the use of F_FSCTL in sys/fcntl.h, _FCNO() & friends, and
> _FCNO_FSPRIV() and friends.
> Oh, one thing we probably want to do is, by convention, build the "num"
> parameters like IOCTLs - the upper 8 bits designate subsystem ('L' for LFS
> :-) and the lower 8 bits designate operation. That way something close to

Shouldn't the _FCN*_FSPRIV() macros take three arguments, then ---
subsystem, subsystem-specific command number, and size --- like _IO*()?

> the right thing happens with layered file systems - FCNTLs not in their
> subsystem get passed down.

Until you mount two unionfss on top of one another and want to affect the
lower one :^)
						Konrad Schroder