[patch RFC 37/38] irqdomain/msi: Provide msi_alloc/free_store() callbacks

[Thomas Gleixner <tglx@xxxxxxxxxxxxx>]

For devices which don't have a standard storage for MSI messages like the
upcoming IMS (Interrupt Message Storm) it's required to allocate storage
space before allocating interrupts and after freeing them.

This could be achieved with the existing callbacks, but that would be
awkward because they operate on msi_alloc_info_t which is not uniform
accross architectures. Also these callbacks are invoked per interrupt but
the allocation might have bulk requirements depending on the device.

As such devices can operate on different architectures it is simpler to
have seperate callbacks which operate on struct device. The resulting
storage information has to be stored in struct msi_desc so the underlying
irq chip implementation can retrieve it for the relevant operations.

Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Marc Zyngier <maz@xxxxxxxxxx>
---
 include/linux/msi.h |    8 ++++++++
 kernel/irq/msi.c    |   11 +++++++++++
 2 files changed, 19 insertions(+)

--- a/include/linux/msi.h
+++ b/include/linux/msi.h
@@ -279,6 +279,10 @@ struct msi_domain_info;
  *                     function.
  * @domain_free_irqs:  Optional function to override the default free
  *                     function.
+ * @msi_alloc_store:   Optional callback to allocate storage in a device
+ *                     specific non-standard MSI store
+ * @msi_alloc_free:    Optional callback to free storage in a device
+ *                     specific non-standard MSI store
  *
  * @get_hwirq, @msi_init and @msi_free are callbacks used by
  * msi_create_irq_domain() and related interfaces
@@ -328,6 +332,10 @@ struct msi_domain_ops {
                                             struct device *dev, int nvec);
        void            (*domain_free_irqs)(struct irq_domain *domain,
                                            struct device *dev);
+       int             (*msi_alloc_store)(struct irq_domain *domain,
+                                          struct device *dev, int nvec);
+       void            (*msi_free_store)(struct irq_domain *domain,
+                                           struct device *dev);
 };
 
 /**
--- a/kernel/irq/msi.c
+++ b/kernel/irq/msi.c
@@ -410,6 +410,12 @@ int __msi_domain_alloc_irqs(struct irq_d
        if (ret)
                return ret;
 
+       if (ops->msi_alloc_store) {
+               ret = ops->msi_alloc_store(domain, dev, nvec);
+               if (ret)
+                       return ret;
+       }
+
        for_each_msi_entry(desc, dev) {
                ops->set_desc(&arg, desc);
 
@@ -509,6 +515,8 @@ int msi_domain_alloc_irqs(struct irq_dom
 
 void __msi_domain_free_irqs(struct irq_domain *domain, struct device *dev)
 {
+       struct msi_domain_info *info = domain->host_data;
+       struct msi_domain_ops *ops = info->ops;
        struct msi_desc *desc;
 
        for_each_msi_entry(desc, dev) {
@@ -522,6 +530,9 @@ void __msi_domain_free_irqs(struct irq_d
                        desc->irq = 0;
                }
        }
+
+       if (ops->msi_free_store)
+               ops->msi_free_store(domain, dev);
 }
 
 /**