[openib-general] Re: [PATCHv2] kDAPL: remove DAT_RETURN

[Grant Grundler]

Caitlin,
there has been sufficient discussion about user vs kernel space
on this list in the past. I'll recap key points. But you'll want
to use google (or something) to read some of the previous
discussion on this topic.

On Fri, May 13, 2005 at 11:52:34AM -0700, Caitlin Bestler wrote:
> What about kernel clients that are compiled separately from the kernel
> that want to be OS neutral and use kdat.h as published by the DAT
> Collaborative?

There is no such thing as OS neutral code when we are talking about
kernel support.  Some code ports more easily between OSs.

Open source community is sensitive to this issue only because
the support model is different.

> Secondly, many routines are identical in user and kernel (in fact the
> common directory is bigger than either the udapl or kdapl directory
> on the sourceforge implementation) requiring that this code be
> maintained in parallel for the kernel and partner udapl librarires
> seems like a lot of extra long term work.

kernel and user space do not have the same requirements.
kernel is ultimately responsible for enforcing userspace policies
(e.g. security, fairness, access rights, etc).
Some of the code can be shared with userspace, but don't expect
that shared code to be OS agnostic as well.

Bottomline is some of the code will need to be maintained in parallel.

grant