[PATCH 02/11] genirq/msi: Add helper for creating MSI-parent irq domains

[Marc Zyngier <maz@kernel.org>]

Creating an irq domain that serves as an MSI parent requires
a substantial amount of esoteric boiler-plate code, some of
which is often provided twice (such as the bus token).

To make things a bit simpler for the unsuspecting MSI tinkerer,
provide a helper that does it for them, and serves as documentation
of what needs to be provided.

Signed-off-by: Marc Zyngier <maz@kernel.org>
---
 include/linux/msi.h |  7 +++++++
 kernel/irq/msi.c    | 40 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 47 insertions(+)

diff --git a/include/linux/msi.h b/include/linux/msi.h
index b10093c4d00ea..f08d14cf07103 100644
--- a/include/linux/msi.h
+++ b/include/linux/msi.h
@@ -594,6 +594,13 @@ struct irq_domain *msi_create_irq_domain(struct fwnode_handle *fwnode,
 					 struct msi_domain_info *info,
 					 struct irq_domain *parent);
 
+struct irq_domain *msi_create_parent_irq_domain(struct fwnode_handle *fwnode,
+						const struct msi_parent_ops *msi_parent_ops,
+						const struct irq_domain_ops *ops,
+						unsigned long flags, unsigned long size,
+						void *host_data,
+						struct irq_domain *parent);
+
 bool msi_create_device_irq_domain(struct device *dev, unsigned int domid,
 				  const struct msi_domain_template *template,
 				  unsigned int hwsize, void *domain_data,
diff --git a/kernel/irq/msi.c b/kernel/irq/msi.c
index 396a067a8a56b..037d85cf0b21c 100644
--- a/kernel/irq/msi.c
+++ b/kernel/irq/msi.c
@@ -885,6 +885,46 @@ struct irq_domain *msi_create_irq_domain(struct fwnode_handle *fwnode,
 	return __msi_create_irq_domain(fwnode, info, 0, parent);
 }
 
+/**
+ * msi_create_parent_irq_domain - Create an MSI-parent interrupt domain
+ * @fwnode:		Optional fwnode of the interrupt controller
+ * @msi_parent_ops:	MSI parent callbacks and configuration
+ * @ops:		Interrupt domain ballbacks
+ * @flags:		Interrupt domain flags
+ * @size:		Interrupt domain size (0 if arbitrarily large)
+ * @host_data:		Interrupt domain private data
+ * @parent:		Parent irq domain
+ *
+ * Return: pointer to the created &struct irq_domain or %NULL on failure
+ */
+struct irq_domain *msi_create_parent_irq_domain(struct fwnode_handle *fwnode,
+						const struct msi_parent_ops *msi_parent_ops,
+						const struct irq_domain_ops *ops,
+						unsigned long flags, unsigned long size,
+						void *host_data,
+						struct irq_domain *parent)
+{
+	struct irq_domain_info info = {
+		.fwnode		= fwnode,
+		.size		= size,
+		.hwirq_max	= size,
+		.ops		= ops,
+		.host_data	= host_data,
+		.domain_flags	= flags | IRQ_DOMAIN_FLAG_MSI_PARENT,
+		.parent		= parent,
+		.bus_token	= msi_parent_ops->bus_select_token,
+	};
+	struct irq_domain *d;
+
+	d = irq_domain_instantiate(&info);
+	if (IS_ERR(d))
+		return NULL;
+
+	d->msi_parent_ops = msi_parent_ops;
+	return d;
+}
+EXPORT_SYMBOL_GPL(msi_create_parent_irq_domain);
+
 /**
  * msi_parent_init_dev_msi_info - Delegate initialization of device MSI info down
  *				  in the domain hierarchy
-- 
2.39.2