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

3 files changed, 116 insertions, 3 deletions

diff --git a/sys/kern/bus_if.m b/sys/kern/bus_if.m
index c1c0e34..c0924c8 100644
--- a/sys/kern/bus_if.m
+++ b/sys/kern/bus_if.m
@@ -509,7 +509,6 @@ METHOD int bind_intr {
 	int		_cpu;
 } DEFAULT bus_generic_bind_intr;
 
-
 /**
  * @brief Allow (bus) drivers to specify the trigger mode and polarity
  * of the specified interrupt.
@@ -527,6 +526,25 @@ METHOD int config_intr {
 } DEFAULT bus_generic_config_intr;
 
 /**
+ * @brief Allow drivers to associate a description with an active
+ * interrupt handler.
+ *
+ * @param _dev		the parent device of @p _child
+ * @param _child	the device which allocated the resource
+ * @param _irq		the resource representing the interrupt
+ * @param _cookie	the cookie value returned when the interrupt
+ *			was originally registered
+ * @param _descr	the description to associate with the interrupt
+ */
+METHOD int describe_intr {
+	device_t	_dev;
+	device_t	_child;
+	struct resource *_irq;
+	void		*_cookie;
+	const char	*_descr;
+} DEFAULT bus_generic_describe_intr;
+
+/**
  * @brief Notify a (bus) driver about a child that the hints mechanism
  * believes it has discovered.
  *
diff --git a/sys/kern/kern_intr.c b/sys/kern/kern_intr.c
index 3eb2c6c..42d5f16 100644
--- a/sys/kern/kern_intr.c
+++ b/sys/kern/kern_intr.c
@@ -524,7 +524,7 @@ intr_event_add_handler(struct intr_event *ie, const char *name,
 	ih->ih_filter = filter;
 	ih->ih_handler = handler;
 	ih->ih_argument = arg;
-	ih->ih_name = name;
+	strlcpy(ih->ih_name, name, sizeof(ih->ih_name));
 	ih->ih_event = ie;
 	ih->ih_pri = pri;
 	if (flags & INTR_EXCL)
@@ -597,7 +597,7 @@ intr_event_add_handler(struct intr_event *ie, const char *name,
 	ih->ih_filter = filter;
 	ih->ih_handler = handler;
 	ih->ih_argument = arg;
-	ih->ih_name = name;
+	strlcpy(ih->ih_name, name, sizeof(ih->ih_name));
 	ih->ih_event = ie;
 	ih->ih_pri = pri;
 	if (flags & INTR_EXCL)
@@ -665,6 +665,61 @@ intr_event_add_handler(struct intr_event *ie, const char *name,
 #endif
 
 /*
+ * Append a description preceded by a ':' to the name of the specified
+ * interrupt handler.
+ */
+int
+intr_event_describe_handler(struct intr_event *ie, void *cookie,
+    const char *descr)
+{
+	struct intr_handler *ih;
+	size_t space;
+	char *start;
+
+	mtx_lock(&ie->ie_lock);
+#ifdef INVARIANTS
+	TAILQ_FOREACH(ih, &ie->ie_handlers, ih_next) {
+		if (ih == cookie)
+			break;
+	}
+	if (ih == NULL) {
+		mtx_unlock(&ie->ie_lock);
+		panic("handler %p not find in interrupt event %p", cookie, ie);
+	}
+#endif
+	ih = cookie;
+
+	/*
+	 * Look for an existing description by checking for an
+	 * existing ":".  This assumes device names do not include
+	 * colons.  If one is found, prepare to insert the new
+	 * description at that point.  If one is not found, find the
+	 * end of the name to use as the insertion point.
+	 */
+	start = index(ih->ih_name, ':');
+	if (start == NULL)
+		start = index(ih->ih_name, 0);
+
+	/*
+	 * See if there is enough remaining room in the string for the
+	 * description + ":".  The "- 1" leaves room for the trailing
+	 * '\0'.  The "+ 1" accounts for the colon.
+	 */
+	space = sizeof(ih->ih_name) - (start - ih->ih_name) - 1;
+	if (strlen(descr) + 1 > space) {
+		mtx_unlock(&ie->ie_lock);
+		return (ENOSPC);
+	}
+
+	/* Append a colon followed by the description. */
+	*start = ':';
+	strcpy(start + 1, descr);
+	intr_event_update(ie);
+	mtx_unlock(&ie->ie_lock);
+	return (0);
+}
+
+/*
  * Return the ie_source field from the intr_event an intr_handler is
  * associated with.
  */
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