linux-kernel - Re: [PATCH v1] gpio: dwapb: mask/unmask IRQ when disable/enable it

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Date: Fri, 15 Dec 2023 13:24:24 +0300
From: Serge Semin <fancer.lancer@...il.com>
To: Thomas Gleixner <tglx@...utronix.de>
Cc: Linus Walleij <linus.walleij@...aro.org>, 
	Luo Jiaxing <luojiaxing@...wei.com>, Marc Zyngier <maz@...nel.org>, 
	Bartosz Golaszewski <bgolaszewski@...libre.com>, Serge Semin <Sergey.Semin@...kalelectronics.ru>, 
	Andy Shevchenko <andy.shevchenko@...il.com>, Andy Shevchenko <andriy.shevchenko@...ux.intel.com>, 
	"open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, 
	Linuxarm <linuxarm@...wei.com>
Subject: Re: [PATCH v1] gpio: dwapb: mask/unmask IRQ when disable/enable it

Hi Thomas

On Fri, Dec 15, 2023 at 09:09:09AM +0100, Thomas Gleixner wrote:
> On Sat, Dec 05 2020 at 22:58, Linus Walleij wrote:
> > Sorry for top posting but I need the help of the irqchip maintainer
> > Marc Z to hash this out.
> >
> > The mask/unmask/disable/enable semantics is something that
> > you need to work with every day to understand right.
> 
> The patch is correct.
> 
> The irq_enable() callback is required to be a superset of
> irq_unmask(). I.e. the core code expects it to do:
> 
>   1) Some preparatory work to enable the interrupt line
> 
>   2) Unmask the interrupt, which is why the masked state is cleared
>      by the core after invoking the irq_enable() callback.
> 
> #2 is pretty obvious because if an interrupt chip does not implement the
> irq_enable() callback the core defaults to irq_unmask()
> 
> Correspondingly the core expects from the irq_disable() callback:
> 
>    1) To mask the interrupt
> 
>    2) To do some extra work to disable the interrupt line
> 
> Same reasoning as above vs. #1 as the core fallback is to invoke the
> irq_unmask() callback when the irq_disable() callback is not
> implemented.

Just curious. Wouldn't that be more correct/portable for the core to
call both callbacks when it's required and if both are provided? So
the supersetness requirement would be no longer applied to the
IRQ enable/disable callbacks implementation thus avoiding the code
duplications in the low-level drivers.

-Serge(y)

> 
> Thanks,
> 
>         tglx
>