linux-kernel - Re: [PATCH 1/2] irqdomain: support three-cell scheme interrupts

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Message-ID: <20250227204155-GYA51171@gentoo>
Date: Thu, 27 Feb 2025 20:41:55 +0000
From: Yixun Lan <dlan@...too.org>
To: Alex Elder <elder@...cstar.com>
Cc: Linus Walleij <linus.walleij@...aro.org>,
	Bartosz Golaszewski <brgl@...ev.pl>,
	Thomas Gleixner <tglx@...utronix.de>,
	Inochi Amaoto <inochiama@...il.com>, linux-kernel@...r.kernel.org,
	linux-gpio@...r.kernel.org, linux-riscv@...ts.infradead.org,
	spacemit@...ts.linux.dev
Subject: Re: [PATCH 1/2] irqdomain: support three-cell scheme interrupts


On 10:12 Thu 27 Feb     , Alex Elder wrote:
> On 2/27/25 5:24 AM, Yixun Lan wrote:
> > The is a prerequisite patch to support parsing three-cell
> > interrupts which encoded as <instance hwirq irqflag>,
> > the translate function will always retrieve irq number and
> > flag from last two cells.
> > 
> > Signed-off-by: Yixun Lan <dlan@...too.org>
> > ---
> >   kernel/irq/irqdomain.c | 11 +++++++++--
> >   1 file changed, 9 insertions(+), 2 deletions(-)
> > 
> > diff --git a/kernel/irq/irqdomain.c b/kernel/irq/irqdomain.c
> > index ec6d8e72d980f604ded2bfa2143420e0e0095920..cb874ab5e54a4763d601122becd63b6d759e55d2 100644
> > --- a/kernel/irq/irqdomain.c
> > +++ b/kernel/irq/irqdomain.c
> > @@ -1208,10 +1208,17 @@ int irq_domain_translate_twocell(struct irq_domain *d,
> >   				 unsigned long *out_hwirq,
> >   				 unsigned int *out_type)
> >   {
> 
> This function is meant for "twocell".  There is also another function
> irq_domain_translate_onecell().  Why don't you just create
> irq_domain_translate_threecell" instead?
> 
good question!

it's too many changes for adding "threecell" which I thought not worth
the effort, or maybe we can rename the function to *twothreecell()?

I'm not sure which way to go is the best, ideas from maintainer are
welcome

> 
> > +	u32 irq, type;
> > +
> >   	if (WARN_ON(fwspec->param_count < 2))
> >   		return -EINVAL;
> > -	*out_hwirq = fwspec->param[0];
> > -	*out_type = fwspec->param[1] & IRQ_TYPE_SENSE_MASK;
> > +
> > +	irq = fwspec->param_count - 2;
> > +	type = fwspec->param_count - 1;
no matter two or three cell, it's always parse the last two cells,
virtually they are same syntax, which can reuse the *_translate_twocell()
function perfectly..

> > +
> > +	*out_hwirq = fwspec->param[irq];
> > +	*out_type = fwspec->param[type] & IRQ_TYPE_SENSE_MASK;
> > +
> >   	return 0;
> >   }
> >   EXPORT_SYMBOL_GPL(irq_domain_translate_twocell);
> > 
> 

-- 
Yixun Lan (dlan)
Gentoo Linux Developer
GPG Key ID AABEFD55