A MSI device may have multiple interrupts. That means that the
interrupts numbers should be continuos so that pdev->irq refers to the
first interrupt, pdev->irq + 1 to the second and so on.
This patch adds support for continuous allocation of virqs for a range
of hwirqs. The function is based on irq_create_mapping() but due to the
number argument there is very little in common now.

Cc: Thomas Gleixner <t...@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bige...@linutronix.de>
---
Scott, this is what you suggested. I must admit, it does not look that
bad. It is just compile tested.

v1.v2:
    - use irq_create_mapping_block() for irq_create_mapping()

 include/linux/irqdomain.h | 10 ++++--
 kernel/irq/irqdomain.c    | 87 ++++++++++++++++++++++++++++++++++-------------
 2 files changed, 72 insertions(+), 25 deletions(-)

diff --git a/include/linux/irqdomain.h b/include/linux/irqdomain.h
index c983ed1..8b09a6b 100644
--- a/include/linux/irqdomain.h
+++ b/include/linux/irqdomain.h
@@ -171,12 +171,18 @@ extern int irq_domain_associate(struct irq_domain 
*domain, unsigned int irq,
                                        irq_hw_number_t hwirq);
 extern void irq_domain_associate_many(struct irq_domain *domain,
                                      unsigned int irq_base,
                                      irq_hw_number_t hwirq_base, int count);
 
-extern unsigned int irq_create_mapping(struct irq_domain *host,
-                                      irq_hw_number_t hwirq);
+extern unsigned int irq_create_mapping_block(struct irq_domain *host,
+               irq_hw_number_t hwirq, unsigned int num);
+static inline unsigned int irq_create_mapping(struct irq_domain *host,
+               irq_hw_number_t hwirq)
+{
+       return irq_create_mapping_block(host, hwirq, 1);
+}
+
 extern void irq_dispose_mapping(unsigned int virq);
 
 /**
  * irq_linear_revmap() - Find a linux irq from a hw irq number.
  * @domain: domain owning this hardware interrupt
diff --git a/kernel/irq/irqdomain.c b/kernel/irq/irqdomain.c
index cf68bb3..cdc6627 100644
--- a/kernel/irq/irqdomain.c
+++ b/kernel/irq/irqdomain.c
@@ -372,67 +372,108 @@ unsigned int irq_create_direct_mapping(struct irq_domain 
*domain)
 
        return virq;
 }
 EXPORT_SYMBOL_GPL(irq_create_direct_mapping);
 
+static int irq_check_continuous_mapping(struct irq_domain *domain,
+               irq_hw_number_t hwirq, unsigned int num)
+{
+       int virq;
+       int i;
+
+       virq = irq_find_mapping(domain, hwirq);
+
+       for (i = 1; i < num; i++) {
+               unsigned int next;
+
+               next = irq_find_mapping(domain, hwirq + i);
+               if (next == virq + i)
+                       continue;
+
+               pr_err("irq: invalid partial mapping. First hwirq %lu maps to "
+                               "%d and \n", hwirq, virq);
+               pr_err("irq: +%d hwirq (%lu) maps to %d but should be %d.\n",
+                               i, hwirq + i, next, virq + i);
+               return -EINVAL;
+       }
+
+       pr_debug("-> existing mapping on virq %d\n", virq);
+       return virq;
+}
+
 /**
- * irq_create_mapping() - Map a hardware interrupt into linux irq space
+ * irq_create_mapping_block() - Map multiple hardware interrupts
  * @domain: domain owning this hardware interrupt or NULL for default domain
  * @hwirq: hardware irq number in that domain space
+ * @num: number of interrupts
+ *
+ * Maps a hwirq to a newly allocated virq. If num is greater than 1 then num
+ * hwirqs (hwirq … hwirq + num - 1) will be mapped and virq will be  
continuous.
+ * Returns the first linux virq number.
  *
- * Only one mapping per hardware interrupt is permitted. Returns a linux
- * irq number.
  * If the sense/trigger is to be specified, set_irq_type() should be called
  * on the number returned from that call.
  */
-unsigned int irq_create_mapping(struct irq_domain *domain,
-                               irq_hw_number_t hwirq)
+unsigned int irq_create_mapping_block(struct irq_domain *domain,
+               irq_hw_number_t hwirq, unsigned int num)
 {
-       unsigned int hint;
        int virq;
+       int i;
+       int node;
+       unsigned int hint;
 
-       pr_debug("irq_create_mapping(0x%p, 0x%lx)\n", domain, hwirq);
+       pr_debug("%s(0x%p, 0x%lx, %d)\n", __func__, domain, hwirq, num);
 
        /* Look for default domain if nececssary */
-       if (domain == NULL)
+       if (!domain && num == 1)
                domain = irq_default_domain;
+
        if (domain == NULL) {
                WARN(1, "%s(, %lx) called with NULL domain\n", __func__, hwirq);
                return 0;
        }
        pr_debug("-> using domain @%p\n", domain);
 
        /* Check if mapping already exists */
-       virq = irq_find_mapping(domain, hwirq);
-       if (virq) {
-               pr_debug("-> existing mapping on virq %d\n", virq);
-               return virq;
+       for (i = 0; i < num; i++) {
+               virq = irq_find_mapping(domain, hwirq + i);
+               if (virq != NO_IRQ) {
+                       if (i == 0)
+                               return irq_check_continuous_mapping(domain,
+                                               hwirq, num);
+                       pr_err("irq: hwirq %ld has no mapping but hwirq %ld "
+                               "maps to virq %d. This can't be a block\n",
+                               hwirq, hwirq + i, virq);
+                       return -EINVAL;
+               }
        }
 
+       node = of_node_to_nid(domain->of_node);
        /* Allocate a virtual interrupt number */
        hint = hwirq % nr_irqs;
        if (hint == 0)
                hint++;
-       virq = irq_alloc_desc_from(hint, of_node_to_nid(domain->of_node));
-       if (virq <= 0)
-               virq = irq_alloc_desc_from(1, of_node_to_nid(domain->of_node));
+       virq = irq_alloc_descs_from(hint, num, node);
+       if (virq <= 0 && hint != 1)
+               virq = irq_alloc_descs_from(1, num, node);
        if (virq <= 0) {
                pr_debug("-> virq allocation failed\n");
                return 0;
        }
 
-       if (irq_domain_associate(domain, virq, hwirq)) {
-               irq_free_desc(virq);
-               return 0;
+       irq_domain_associate_many(domain, virq, hwirq, num);
+       if (num == 1) {
+               pr_debug("irq %lu on domain %s mapped to virtual irq %u\n",
+                       hwirq, of_node_full_name(domain->of_node), virq);
+               return virq;
        }
-
-       pr_debug("irq %lu on domain %s mapped to virtual irq %u\n",
-               hwirq, of_node_full_name(domain->of_node), virq);
-
+       pr_debug("irqs %lu…%lu on domain %s mapped to virtual irqs %u…%u\n",
+               hwirq, hwirq + num - 1, of_node_full_name(domain->of_node),
+                       virq, virq + num - 1);
        return virq;
 }
-EXPORT_SYMBOL_GPL(irq_create_mapping);
+EXPORT_SYMBOL_GPL(irq_create_mapping_block);
 
 /**
  * irq_create_strict_mappings() - Map a range of hw irqs to fixed linux irqs
  * @domain: domain owning the interrupt range
  * @irq_base: beginning of linux IRQ range
-- 
1.9.0.rc3

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