Add a facility for associating optional descriptions with active interrupt

handlers.  This is primarily intended as a way to allow devices that use
multiple interrupts (e.g. MSI) to meaningfully distinguish the various
interrupt handlers.
- Add a new BUS_DESCRIBE_INTR() method to the bus interface to associate
  a description with an active interrupt handler setup by BUS_SETUP_INTR.
  It has a default method (bus_generic_describe_intr()) which simply passes
  the request up to the parent device.
- Add a bus_describe_intr() wrapper around BUS_DESCRIBE_INTR() that supports
  printf(9) style formatting using var args.
- Reserve MAXCOMLEN bytes in the intr_handler structure to hold the name of
  an interrupt handler and copy the name passed to intr_event_add_handler()
  into that buffer instead of just saving the pointer to the name.
- Add a new intr_event_describe_handler() which appends a description string
  to an interrupt handler's name.
- Implement support for interrupt descriptions on amd64 and i386 by having
  the nexus(4) driver supply a custom bus_describe_intr method that invokes
  a new intr_describe() MD routine which in turn looks up the associated
  interrupt event and invokes intr_event_describe_handler().

Requested by:	many
Reviewed by:	scottl
MFC after:	2 weeks

1 files changed, 40 insertions, 0 deletions

diff --git a/sys/kern/subr_bus.c b/sys/kern/subr_bus.c
index 3f51c5c..e4d1f9b 100644
--- a/sys/kern/subr_bus.c
+++ b/sys/kern/subr_bus.c
@@ -3520,6 +3520,24 @@ bus_generic_config_intr(device_t dev, int irq, enum intr_trigger trig,
 }
 
 /**
+ * @brief Helper function for implementing BUS_DESCRIBE_INTR().
+ *
+ * This simple implementation of BUS_DESCRIBE_INTR() simply calls the
+ * BUS_DESCRIBE_INTR() method of the parent of @p dev.
+ */
+int
+bus_generic_describe_intr(device_t dev, device_t child, struct resource *irq,
+    void *cookie, const char *descr)
+{
+
+	/* Propagate up the bus hierarchy until someone handles it. */
+	if (dev->parent)
+		return (BUS_DESCRIBE_INTR(dev->parent, child, irq, cookie,
+		    descr));
+	return (EINVAL);
+}
+
+/**
  * @brief Helper function for implementing BUS_GET_DMA_TAG().
  *
  * This simple implementation of BUS_GET_DMA_TAG() simply calls the
@@ -3824,6 +3842,28 @@ bus_bind_intr(device_t dev, struct resource *r, int cpu)
 }
 
 /**
+ * @brief Wrapper function for BUS_DESCRIBE_INTR().
+ *
+ * This function first formats the requested description into a
+ * temporary buffer and then calls the BUS_DESCRIBE_INTR() method of
+ * the parent of @p dev.
+ */
+int
+bus_describe_intr(device_t dev, struct resource *irq, void *cookie,
+    const char *fmt, ...)
+{
+	char descr[MAXCOMLEN];
+	va_list ap;
+
+	if (dev->parent == NULL)
+		return (EINVAL);
+	va_start(ap, fmt);
+	vsnprintf(descr, sizeof(descr), fmt, ap);
+	va_end(ap);
+	return (BUS_DESCRIBE_INTR(dev->parent, dev, irq, cookie, descr));
+}
+
+/**
  * @brief Wrapper function for BUS_SET_RESOURCE().
  *
  * This function simply calls the BUS_SET_RESOURCE() method of the