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

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Message-ID: <cc95d9b3-f18d-febc-0a51-cc3846d0de85@arm.com>
Date:   Thu, 5 Oct 2017 11:59:46 +0100
From:   Marc Zyngier <marc.zyngier@....com>
To:     Linus Walleij <linus.walleij@...aro.org>,
        Jerome Brunet <jbrunet@...libre.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 21/09/17 12:41, Linus Walleij wrote:
> 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.
Unfortunately, there is no such thing. I contemplated tracking this at
some point, and got sidetracked. In general, the irq domain and irq core
are horribly disconnected, leading to that exact line of questioning.

	M.
-- 
Jazz is not dead. It just smells funny...