ACPI: irq: Introduce acpi_get_gsi_dispatcher()

Using acpi_irq_create_hierarchy() in the cases where the code
also handles OF leads to code duplication as the ACPI subsystem
doesn't provide means to compute the IRQ domain parent whereas
the OF does.

Introduce acpi_get_gsi_dispatcher() so that the drivers relying
on both ACPI and OF may use irq_domain_create_hierarchy() in the
common code paths.

No functional changes.

Signed-off-by: Roman Kisel <romank@linux.microsoft.com>
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Link: https://lore.kernel.org/r/20250428210742.435282-11-romank@linux.microsoft.com
Signed-off-by: Wei Liu <wei.liu@kernel.org>
Message-ID: <20250428210742.435282-11-romank@linux.microsoft.com>

Author: romank-msft

drivers/acpi/irq.c

@@ -12,7 +12,7 @@
 
 enum acpi_irq_model_id acpi_irq_model;
 
-static struct fwnode_handle *(*acpi_get_gsi_domain_id)(u32 gsi);
+static acpi_gsi_domain_disp_fn acpi_get_gsi_domain_id;
 static u32 (*acpi_gsi_to_irq_fallback)(u32 gsi);
 
 /**
@@ -307,12 +307,24 @@ EXPORT_SYMBOL_GPL(acpi_irq_get);
  *	for a given GSI
  */
 void __init acpi_set_irq_model(enum acpi_irq_model_id model,
-			       struct fwnode_handle *(*fn)(u32))
+			       acpi_gsi_domain_disp_fn fn)
 {
 	acpi_irq_model = model;
 	acpi_get_gsi_domain_id = fn;
 }
 
+/*
+ * acpi_get_gsi_dispatcher() - Get the GSI dispatcher function
+ *
+ * Return the dispatcher function that computes the domain fwnode for
+ * a given GSI.
+ */
+acpi_gsi_domain_disp_fn acpi_get_gsi_dispatcher(void)
+{
+	return acpi_get_gsi_domain_id;
+}
+EXPORT_SYMBOL_GPL(acpi_get_gsi_dispatcher);
+
 /**
  * acpi_set_gsi_to_irq_fallback - Register a GSI transfer
  * callback to fallback to arch specified implementation.

include/linux/acpi.h

@@ -335,8 +335,11 @@ int acpi_register_gsi (struct device *dev, u32 gsi, int triggering, int polarity
 int acpi_gsi_to_irq (u32 gsi, unsigned int *irq);
 int acpi_isa_irq_to_gsi (unsigned isa_irq, u32 *gsi);
 
+typedef struct fwnode_handle *(*acpi_gsi_domain_disp_fn)(u32);
+
 void acpi_set_irq_model(enum acpi_irq_model_id model,
-			struct fwnode_handle *(*)(u32));
+			acpi_gsi_domain_disp_fn fn);
+acpi_gsi_domain_disp_fn acpi_get_gsi_dispatcher(void);
 void acpi_set_gsi_to_irq_fallback(u32 (*)(u32));
 
 struct irq_domain *acpi_irq_create_hierarchy(unsigned int flags,