linux-kernel - Re: [RFT PATCH v2] gpiolib: allow gpio irqchip to map irqs dynamically

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Message-ID: <CACRpkdZAJ1c6VyHA+2P6P4GaMY51q-ANc2NLF_2o4atzz2mqrg@mail.gmail.com>
Date:   Thu, 21 Sep 2017 13:41:45 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Jerome Brunet <jbrunet@...libre.com>,
        Marc Zyngier <marc.zyngier@....com>,
        Rob Herring <robh@...nel.org>
Cc:     Grygorii Strashko <grygorii.strashko@...com>,
        Bartosz Golaszewski <brgl@...ev.pl>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFT PATCH v2] gpiolib: allow gpio irqchip to map irqs dynamically

On Fri, Sep 15, 2017 at 10:26 AM, Jerome Brunet <jbrunet@...libre.com> wrote:

> I initially planned to do some refcounting in the gpio layer but that would make
> no sense, as you pointed out, the irq could be shared. This refcounting would
> only make sense at the irq level.
>
> On a more general note, I wonder when is it safe for a driver to dispose of the
> mapping of a possibly shared irq ? There is no way to know if the mapping is
> still used somewhere else, or am I missing something again ?

I have no idea, but maybe Marc Z or Rob H knows this?

They usually have a bit of deeper IRQ-centric knowledge.

Yours,
Linus Walleij