linux-kernel - Re: [PATCH v3] irqchip/tango: Don't use incorrect irq_mask

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Date:   Tue, 25 Jul 2017 14:29:20 +0100
From:   Måns Rullgård <mans@...sr.com>
To:     Marc Gonzalez <marc_gonzalez@...madesigns.com>
Cc:     Doug Berger <opendmb@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Marc Zyngier <marc.zyngier@....com>,
        Jason Cooper <jason@...edaemon.net>,
        Florian Fainelli <f.fainelli@...il.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Mason <slash.tmp@...e.fr>
Subject: Re: [PATCH v3] irqchip/tango: Don't use incorrect irq_mask_ack callback

Marc Gonzalez <marc_gonzalez@...madesigns.com> writes:

> On 25/07/2017 15:16, Måns Rullgård wrote:
>
>> What happened to the patch adding the proper combined function?
>
> It appears you're not CCed on v2.
>
> https://patchwork.kernel.org/patch/9859799/
>
> Doug wrote:
>> Yes, you understand correctly.  The irq_mask_ack method is entirely
>> optional and I assume that is why this issue went undetected for so
>> long; however, it is slightly more efficient to combine the functions
>> (even if the ack is unnecessary) which is why I chose to do so for my
>> changes to the irqchip-brcmstb-l2 driver where I first discovered this
>> issue.  How much value the improved efficiency has is certainly
>> debatable, but interrupt handling is one area where people might care
>> about such a small difference.  As the irqchip-tango driver maintainer
>> you are welcome to decide whether or not the irq_mask_ack method makes
>> sense to you.
>
> My preference goes to leaving the irq_mask_ack callback undefined,
> and let the irqchip framework use irq_mask and irq_ack instead.

Why would you prefer the less efficient way?

-- 
Måns Rullgård