On Wed, Oct 26, 2016 at 4:22 PM, Jerome Brunet [off-list ref] wrote:

On Tue, 2016-10-25 at 20:20 +0200, Linus Walleij wrote:

quoted

However the semantic is such, that it is not necessary to call
to_irq()
before using an IRQ: the irqchip and gpiochip abstractions should be
orthogonal.

Linus,

They are orthogonal. You can request an irq from the irqchip controller
without the gpiochip, like any other irq controller.

OK good, sorry if I'm stating the obvious.

irq_create_mapping (and irq_create_fwspec_mapping) internally calls
irq_find_mapping. So if the mapping already exist (the irq is already
used before calling to_irq), the existing mapping will be returned. The
mapping will be actually created only if needed. It seems to be in line
with your explanation, no ?

Yes, but you want to call irq_create_mapping() in slowpath (irq setup)
and irq_find_mapping() in fastpath (irq handler). Else the first IRQ
may result in unwelcomed surprises.

There is really a *lot* of gpio drivers which use irq_create_mapping in
the to_irq callback, are these all wrong ?

Yes they are all wrong. They should all be using irq_find_mapping().

If this should not be used, what should we all do instead ?

Call irq_create_mapping() in some other place.

Yours,
Linus Walleij
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