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

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Message-ID: <20260105120108.00002016@huawei.com>
Date: Mon, 5 Jan 2026 12:01:08 +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 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.

> ---
>  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.

Or go with something similar to named and have

irq_domain_alloc_named_parented_fwnode()?

I'm not that bothered though if you think the current naming is the best we can do.

Jonathan

> +{
> +	return __irq_domain_alloc_fwnode(IRQCHIP_FWNODE_NAMED, 0, name, NULL, parent);
>  }