linux-kernel - Re: [PATCH v2 3/7] irqdomain: Add parent field to struct irqchip

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Message-ID: <20260107100452.00004b6f@huawei.com>
Date: Wed, 7 Jan 2026 10:04:52 +0000
From: Jonathan Cameron <jonathan.cameron@...wei.com>
To: Lorenzo Pieralisi <lpieralisi@...nel.org>
CC: "Rafael J. Wysocki" <rafael@...nel.org>, Len Brown <lenb@...nel.org>,
	Robert Moore <robert.moore@...el.com>, Thomas Gleixner <tglx@...utronix.de>,
	Hanjun Guo <guohanjun@...wei.com>, Sudeep Holla <sudeep.holla@....com>, Marc
 Zyngier <maz@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>,
	<linux-acpi@...r.kernel.org>, <acpica-devel@...ts.linux.dev>,
	<linux-kernel@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>,
	<linux-pci@...r.kernel.org>
Subject: Re: [PATCH v2 3/7] irqdomain: Add parent field to struct
 irqchip_fwid

On Wed, 7 Jan 2026 09:58:07 +0100
Lorenzo Pieralisi <lpieralisi@...nel.org> wrote:

> On Mon, Jan 05, 2026 at 12:01:08PM +0000, Jonathan Cameron wrote:
> > On Thu, 18 Dec 2025 11:14:29 +0100
> > Lorenzo Pieralisi <lpieralisi@...nel.org> wrote:
> >   
> > > The GICv5 driver IRQ domain hierarchy requires adding a parent field to
> > > struct irqchip_fwid so that core code can reference a fwnode_handle parent
> > > for a given fwnode.
> > > 
> > > Add a parent field to struct irqchip_fwid and update the related kernel API
> > > functions to initialize and handle it.
> > > 
> > > Signed-off-by: Lorenzo Pieralisi <lpieralisi@...nel.org>
> > > Cc: Thomas Gleixner <tglx@...utronix.de>
> > > Cc: Marc Zyngier <maz@...nel.org>  
> > Hi Lorenzo,
> > 
> > Happy new year.  
> 
> Happy New Year !
> 
> > > ---
> > >  include/linux/irqdomain.h | 30 ++++++++++++++++++++++++++----
> > >  kernel/irq/irqdomain.c    | 14 +++++++++++++-
> > >  2 files changed, 39 insertions(+), 5 deletions(-)
> > > 
> > > diff --git a/include/linux/irqdomain.h b/include/linux/irqdomain.h
> > > index 62f81bbeb490..b9df84b447a1 100644
> > > --- a/include/linux/irqdomain.h
> > > +++ b/include/linux/irqdomain.h
> > > @@ -257,7 +257,8 @@ static inline void irq_domain_set_pm_device(struct irq_domain *d, struct device
> > >  
> > >  #ifdef CONFIG_IRQ_DOMAIN
> > >  struct fwnode_handle *__irq_domain_alloc_fwnode(unsigned int type, int id,
> > > -						const char *name, phys_addr_t *pa);
> > > +						const char *name, phys_addr_t *pa,
> > > +						struct fwnode_handle *parent);
> > >  
> > >  enum {
> > >  	IRQCHIP_FWNODE_REAL,
> > > @@ -267,18 +268,39 @@ enum {
> > >  
> > >  static inline struct fwnode_handle *irq_domain_alloc_named_fwnode(const char *name)
> > >  {
> > > -	return __irq_domain_alloc_fwnode(IRQCHIP_FWNODE_NAMED, 0, name, NULL);
> > > +	return __irq_domain_alloc_fwnode(IRQCHIP_FWNODE_NAMED, 0, name, NULL, NULL);
> > > +}
> > > +
> > > +static inline
> > > +struct fwnode_handle *irq_domain_alloc_named_fwnode_parent(const char *name,
> > > +							   struct fwnode_handle *parent)  
> > 
> > The name of this makes me think it's allocating the named fwnode parent, rather that
> > the named fwnode + setting it's parent.
> > 
> > There aren't all that many calls to irq_domain_named_fwnode(), maybe to avoid challenge
> > of a new name, just add the parameter to all of them? (25ish)  Mind you the current
> > pattern for similar cases is a helper, so maybe not.  
> 
> Similar cases ? Have you got anything specific I can look into ?

I meant all the different irq_domain_alloc_xxxxx variants that call
__irq_domain_alloc_fwnode() with a subset of parameters set to NULL.

That seems to say there is a precedence for making the presence of the parameter
part of the name rather than requiring callers to set the ones they don't want to
NULL.  So it argues for a helper like this one just for consistency.

> 
> > Or go with something similar to named and have
> > 
> > irq_domain_alloc_named_parented_fwnode()?  
> 
> Or I can add a set_parent() helper (though that's a bit of churn IMO) ?
> 
> If Thomas has a preference I will follow that, all of the above is doable
> for me.

Agreed. Let's see what Thomas prefers (i.e. make the decision his problem ;)

Jonathan

> 
> > I'm not that bothered though if you think the current naming is the best we can do.  
> 
> I think you have a point - as per my comment above.
> 
> Thanks,
> Lorenzo
> 
> > Jonathan
> >   
> > > +{
> > > +	return __irq_domain_alloc_fwnode(IRQCHIP_FWNODE_NAMED, 0, name, NULL, parent);
> > >  }  
> > 
> >   
>