Re: [PATCH v3 3/8] irqchip/al-fic: keep the device_node instead of a cached name string

[Radu Rendec <radu@rendec.net>]

On Mon, 2026-10-05 at 11:24 +0000, Eliav Farber wrote:
> struct al_fic cached a "const char *name" that al_fic_wire_init() received
> as a separate argument and set from node->name. That string aliased
> storage inside the device_node rather than being owned by the driver, but
> nothing in the struct expressed that dependency - al_fic just held a bare
> pointer with no indication of what it pointed into or why it stayed valid.
> 
> This is not fixing a lifetime bug - of_irq_init() takes a reference on
> the node before calling the driver's init callback and never drops it on
> a successful init, so the node is pinned for the life of the system
> either way, and node->name was never actually at risk of dangling.
> 
> Keeping the device_node in the struct instead of the bare name is about
> making the dependency explicit rather than closing a real one: it holds
> the object the name is derived from, and lets each site derive the name
> on demand instead of carrying a pointer whose validity nothing in the
> struct asserts.
> 
> The irqchip callback that has no device_node in scope now prints the
> instance with %pOF, which formats the node on demand, and the name argument
> threaded through al_fic_wire_init() goes away.
> 
> irq_alloc_domain_generic_chips() keeps the pointer it is given, so it now
> uses of_node_full_name(). This changes the generic chip name from the bare
> node name (e.g. "interrupt-controller") to the full node name including
> its unit address (e.g. "interrupt-controller@fd8a8500"), which keeps
> instances that share a bare name distinguishable.
> 
> Signed-off-by: Eliav Farber <farbere@amazon.com>
> ---
> v3:
>  - Use of_node_full_name() instead of reaching into node->full_name
>    directly, as Radu Rendec suggested.
>  - Rewrite the commit message to say plainly that this patch does not fix
>    a lifetime bug. of_irq_init() takes a reference on the node before
>    calling the driver's init callback and does not drop it on a
>    successful init, so the node, and the storage node->name points into,
>    is pinned for the life of the system either way. The value of keeping
>    the device_node is making that dependency explicit, not closing a
>    real one.
> 
> v2: new patch. Keep the device_node in struct al_fic instead of a cached
>     name string that aliased node storage. Introduced here so the struct
>     holds the node before the next patch requests the parent interrupt by
>     node->full_name, keeping every commit buildable on its own.
> 
>  drivers/irqchip/irq-al-fic.c | 13 +++++--------
>  1 file changed, 5 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/irqchip/irq-al-fic.c b/drivers/irqchip/irq-al-fic.c
> index 760bd08dcff4..ee06d0123b7a 100644
> --- a/drivers/irqchip/irq-al-fic.c
> +++ b/drivers/irqchip/irq-al-fic.c
> @@ -36,7 +36,7 @@ enum al_fic_state {
>  struct al_fic {
>  	void __iomem *base;
>  	struct irq_domain *domain;
> -	const char *name;
> +	struct device_node *node;
>  	unsigned int parent_irq;
>  	enum al_fic_state state;
>  };
> @@ -89,7 +89,7 @@ static int al_fic_irq_set_type(struct irq_data *data, unsigned int flow_type)
>  	if (fic->state == AL_FIC_UNCONFIGURED) {
>  		al_fic_set_trigger(fic, gc, new_state);
>  	} else if (fic->state != new_state) {
> -		pr_debug("fic %s state already configured to %d\n", fic->name, fic->state);
> +		pr_debug("fic %pOF state already configured to %d\n", fic->node, fic->state);
>  		return -EINVAL;
>  	}
>  	return 0;
> @@ -142,7 +142,7 @@ static int al_fic_register(struct device_node *node,
>  
>  	ret = irq_alloc_domain_generic_chips(fic->domain,
>  					     NR_FIC_IRQS,
> -					     1, fic->name,
> +					     1, of_node_full_name(fic->node),
>  					     handle_level_irq,
>  					     0, 0, IRQ_GC_INIT_MASK_CACHE);
>  	if (ret) {
> @@ -175,9 +175,8 @@ static int al_fic_register(struct device_node *node,
>  
>  /*
>   * al_fic_wire_init() - initialize and configure fic in wire mode
> - * @of_node: optional pointer to interrupt controller's device tree node.
> + * @node: pointer to the interrupt controller's device tree node
>   * @base: mmio to fic register
> - * @name: name of the fic
>   * @parent_irq: interrupt of parent
>   *
>   * This API will configure the fic hardware to work in wire mode.
> @@ -187,7 +186,6 @@ static int al_fic_register(struct device_node *node,
>   */
>  static struct al_fic *al_fic_wire_init(struct device_node *node,
>  				       void __iomem *base,
> -				       const char *name,
>  				       unsigned int parent_irq)
>  {
>  	struct al_fic *fic;
> @@ -200,7 +198,7 @@ static struct al_fic *al_fic_wire_init(struct device_node *node,
>  
>  	fic->base = base;
>  	fic->parent_irq = parent_irq;
> -	fic->name = name;
> +	fic->node = node;
>  
>  	/* mask out all interrupts */
>  	writel_relaxed(0xFFFFFFFF, fic->base + AL_FIC_MASK);
> @@ -254,7 +252,6 @@ static int __init al_fic_init_dt(struct device_node *node,
>  
>  	fic = al_fic_wire_init(node,
>  			       base,
> -			       node->name,
>  			       parent_irq);
>  	if (IS_ERR(fic)) {
>  		pr_err("%pOF: fail to initialize irqchip (%lu)\n",

Reviewed-by: Radu Rendec <radu@rendec.net>