Re: [RFC PATCH] of: platform: Skip mapping of interrupts in of_device_alloc()

Hi Rob and Marc,

On Thu, Dec 9, 2021 at 10:33 AM Marc Zyngier [off-list ref] wrote:

On Thu, 09 Dec 2021 10:00:44 +0000,
"Lad, Prabhakar" [off-list ref] wrote:

quoted

quoted

The root of the issue is that all the resource allocation is done
upfront, way before we even have a driver that could potentially
deal with this device. This is a potential waste of resource, and
it triggers the issue you noticed.

If you delay the resource allocation until there is an actual
match with a driver, you could have a per-driver flag telling you
whether the IRQ allocation should be performed before the probe()
function is called.

As suggested by Rob, if we switch the drivers to use
platform_get_resource(pdev, IORESOURCE_IRQ, n) call with
platform_get_irq() this code should go away and with this switch the
resource allocation will happen demand. Is this approach OK?

If you get rid of of_irq_to_resource_table() altogether, then yes,
this has a fighting chance to work.

Yes, switching to platform_get_irq() will eventually cause
of_irq_to_resource_table() to go away.

On second thought, instead of touching all the drivers, if we update
platform_get_resource/platform_get_resource_byname to internally call
platform_get_irq() internally if it's a IORESOURCE_IRQ resource. Does
that sound good or should I just get on changing all the drivers to
use platform_get_irq() instead?

Cheers,
Prabhakar

        M.


--
Without deviation from the norm, progress is not possible.