[PATCH 2/2] I/O port access routines

Adam Jackson ajax at redhat.com
Thu Nov 19 10:58:52 PST 2009

On Thu, 2009-11-19 at 18:25 +0100, Luc Verhaegen wrote:

> The baby was thrown out with the bathwater with libpciaccess and vga 
> arbitration, and now suddenly the plan seems to be to put these new 
> enable/disable hooks all over the driver, together with slightly more 
> involved IN/OUT calls.

The enable/disable thing, no.  That wrapping is in the server.  You
don't have to do it from your driver.

You seem to be putting words in my mouth with the in/out stuff though.
I haven't actually said anything (yet) about whether the drivers may
continue to use the old in/out calls.  All I've done here is add API to
the hardware access library to let me get at the third of the three
address spaces the hardware exposes.

Now, drivers _ought_ not use the old API.  And I'm entirely willing to
fix the drivers to use the new API conditional on its presence.  But if
you really want the freedom to make your driver continue to not work
with multiple PCI domains, then I guess that's a choice you can make.

> But there is nothing that stopped people from keeping the upper level 
> infrastructure in place while having reworked the backend to work on top 
> of the now existing nice pci support in the kernel. The only reason 
> to replace the whole thing was rampant NIH.
> And this rampant NIH is the core cause for the big nasty interface 
> change and RAC being #ifdeffed and commented out, without a replacement, 
> for several years.

You're using "NIH" as something of a scarlet letter here.  That's a
thing you can do, although it's sort of comical.  It might even be a
true description of the motivation, for all it matters.  You're also
conflating the RAC and PCI layers a bit more than is deserved.  And I
should point out (again) that I do _not_ think the transition was
handled well.

But, in the end, I think you're mistaken about the practicality of
"reworking the backend".  Taking off and nuking the site from orbit
really was the right move.

All of which is lovely parlour conversation, but doesn't really address
the patch.  I have this feature in mind.  I wrote some code to implement
it.  I think it would make life better.  Are you suggesting that it
would make life worse?

- ajax
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