[dm-devel] Re: [RFC] device-mapper ioctl interface

[Greg KH]

On Mon, Jun 09, 2003 at 10:03:50PM +0200, Daniel Phillips wrote:
> On Friday 06 June 2003 19:17, Greg KH wrote:
> > On Thu, Jun 05, 2003 at 10:39:43AM +0100, Joe Thornber wrote:
> > > Here's the header file for the the proposed new ioctl interface for
> > > dm.  We've tried to change as little as possible to minimise code
> > > changes in LVM2 and EVMS.
> >
> > Minor comment:
> > 	- please do not use uint_32t types in kernel header files.  Use
> > 	  the proper __u32 type which is guarenteed to be the proper
> > 	  size across the user/kernel boundry.
> 
> We even have a flavor without the __'s:
> 
>    http://lxr.linux.no/source/include/asm-i386/types.h?v=2.5.56#L47
> 
> A little easier on the eyes, imho.

But they are not the same.
 - "__" means this variable will be the same size across the
   kernel/userspace boundry.
 - without the "__" means this variable will only be this size within
   the kernel.

Use "__" for variables being seen by userspace.  Otherwise use the
types without "__".

Hope this helps,

greg k-h