Re: [Scst-devel] Fwd: Re: linuxcon 2010...

[Konrad Rzeszutek Wilk]

On Tuesday 24 August 2010 10:51:04 Chris Weiss wrote:
> On Tue, Aug 24, 2010 at 9:41 AM, Vladislav Bolkhovitin <vst@xxxxxxxx> wrote:
> > James Bottomley, on 08/22/2010 12:43 AM wrote:
> >> Interface re-use (or at least ABI compatibility) is the whole point,
> >> it's what makes the solution a drop in replacement.
> >
> > I see now. You want ABI compatibility to keep the "contract" that no
> > kernel changes can break applications binary compatibility for unlimited
> > time.
>
> ok now I'm confused, or maybe I'm not understanding ABI correctly, or
> maybe you guys are using it in a way that is inconsistent with popular

You are thinking of the KABI. That changes per each release except if you buy 
a vendor product. Red Hat for example keeps an KABI symbol list where they 
guarantee that those parameters, structures ,etc will never change. John 
Masters wrote a nice paper about how they solved this:
http://dup.et.redhat.com/presentations/DriverUpdateProgramTechnical.pdf

I don't have experience with other vendors.

In terms of ABI, think ioctl calls and its a parameters. They are suppose to 
stay the same for long long durations.

> convention.   As a VMware user, I have experienced fully that the
> kernel ABI changes in various places with every release.  VMwares
> drivers have to be constantly updated to match changes in kernel
> function parameters and even what functions are available.
>
> I've also experienced it with scsi cards, dsl modems, and other 3rd
> party drivers.  It's the one big downside to developing for the Linux
> kernel, the ABI is /always/ changing.
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