Subject: Re: Per-thread user <-> kernel communication area
To: Bill Stouder-Studenmund <>
From: David Laight <>
List: tech-kern
Date: 11/09/2007 08:55:54
On Thu, Nov 08, 2007 at 04:33:08PM -0800, Bill Stouder-Studenmund wrote:
> 2) What thoughts do you have for versioning this stuff? Specifically, I 
> can see a utility in eventually having the app communicate some things to 
> the kernel via this page. How do we avoid having either side end up 
> waiting for something the other doesn't know to do?
> A sub-comment of the above, once we've added more stuff, how would we 
> handle obsoleting stuff? Say we add something then, after having actually 
> tried it, realize that it's unworkable. How do we get rid of it?

A thought on that is to encode a series of offsets at the start of the page?
At least then individual features can be added/removed without completely
breaking everything.

Possibly even an array of fixed size type+value pairs - where the value
might be an offset into the page.

The layout would be fixed for the kernel, but userspace would have to
scan it (probably once only?) to determine if a specific structure


David Laight: