Re: [PATCH] of/irq: lookup 'interrupts-extended' property first

On Wed, Aug 6, 2014 at 4:50 PM, Tim Bird [off-list ref] wrote:

On Wed, Aug 6, 2014 at 1:12 PM, Brian Norris
[off-list ref] wrote:

quoted

On Wed, Aug 06, 2014 at 01:42:08PM -0500, Rob Herring wrote:

quoted

On Wed, Aug 6, 2014 at 11:54 AM, Brian Norris [off-list ref] wrote:

quoted

On Thu, Jul 31, 2014 at 11:00:01AM -0700, Florian Fainelli wrote:
I think it is important that a device tree provide some flexibility on
kernel versions. We only invented 'interrupts-extended' in Linux 3.13,
so it's easy to have device trees that could work only on 3.13+.

Typically, we might say that new features require new kernels, but this
is a very basic piece of the DT infrastructure. In our case, we have
hardware whose basic features can be supported by a single interrupt
parent, and so we used the 'interrupts' property pre-3.13. But when we
want to add some power management features, there's an additional
interrupt parent. Under the current DT binding, we have to switch over
to using 'interrupts-extended' exclusively, and thus we must have a
completely new DTB for >=3.13, and this DTB no longer works with the old
kernels.

"Must have" to enable the new features?

Yes. The new feature requires an additional interrupt parent, and so it
requires interrupts-extended.

Hold on there.  What about interrupt-map?  That was the traditional DT
feature for
supporting multi-parented interrupts.  Why couldn't the feature have been added
using that instead of interrupts-extended?

It could have, but interrupts-extended is much more simple to express
for the simple case of a device's interrupts routed to more than one
parent.

I know interrupts-extended is preferred, but has interrupt-map support been
removed from recent kernels?  I'm a bit confused.

They are all still supported. It's just a question of order of parsing
if you have find both styles.

Rob