[PATCH v3] genirq: Machine-parsable version of /proc/interrupts

[Craig Gallek]

From: Craig Gallek <kraig@xxxxxxxxxx>

Add struct kobject to struct irq_desc to allow for easy export
to sysfs.  This allows for much simpler userspace-parsing of
the information contained in struct irq_desc.

Note that sysfs is not available at the time of early irq initialization.
These interrupts are accounted for using a postcore_initcall callback.

Examples:
  /sys/kernel/irq/18/actions:	i801_smbus,ehci_hcd:usb1,uhci_hcd:usb7
  /sys/kernel/irq/18/chip_name:	IR-IO-APIC
  /sys/kernel/irq/18/hwirq:		18
  /sys/kernel/irq/18/name:		fasteoi
  /sys/kernel/irq/18/per_cpu_count:	0,0
  /sys/kernel/irq/18/type:		level

  /sys/kernel/irq/25/actions:	ahci0
  /sys/kernel/irq/25/chip_name:	IR-PCI-MSI
  /sys/kernel/irq/25/hwirq:		512000
  /sys/kernel/irq/25/name:		edge
  /sys/kernel/irq/25/per_cpu_count:	29036,0
  /sys/kernel/irq/25/type:		edge

Signed-off-by: Craig Gallek <kraig@xxxxxxxxxx>
---
v3 changes:
 * Add some examples to the commit message and an ABI documentation file.
 * Fix spelling mistake.

v2 changes:
 * Several suggested stylistic changes.
 * Fix one NULL pointer dereference possibility.
 * Do not destroy kobjects in non-SPARSE_IRQ configuration.
 * Include #define CONFIG_SYSFS guards to selectively enable feature.

 Documentation/ABI/testing/sysfs-kernel-irq |  51 ++++++++
 include/linux/irqdesc.h                    |   3 +
 kernel/irq/irqdesc.c                       | 189 ++++++++++++++++++++++++++++-
 3 files changed, 241 insertions(+), 2 deletions(-)
 create mode 100644 Documentation/ABI/testing/sysfs-kernel-irq

diff --git a/Documentation/ABI/testing/sysfs-kernel-irq b/Documentation/ABI/testing/sysfs-kernel-irq
new file mode 100644
index 000000000000..f2ba24640b2b
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-kernel-irq
@@ -0,0 +1,51 @@
+What:		/sys/kernel/irq
+Date:		September 2016
+KernelVersion:	4.9
+Contact:	Craig Gallek <kraig@xxxxxxxxxx>
+Description:	Directory containing information about the system's IRQs.
+		Specifically, data from the associated struct irq_desc.
+		The information here is similar to that in /proc/interrupts
+		but in a more machine-friendly format.  This directory contains
+		one subdirectory for each Linux IRQ number.
+
+What:		/sys/kernel/irq/<irq>/actions
+Date:		September 2016
+KernelVersion:	4.9
+Contact:	Craig Gallek <kraig@xxxxxxxxxx>
+Description:	The IRQ action chain.  A comma-separated list of zero or more
+		device names associated with this interrupt.
+
+What:		/sys/kernel/irq/<irq>/chip_name
+Date:		September 2016
+KernelVersion:	4.9
+Contact:	Craig Gallek <kraig@xxxxxxxxxx>
+Description:	Human-readable chip name supplied by the associated device
+		driver.
+
+What:		/sys/kernel/irq/<irq>/hwirq
+Date:		September 2016
+KernelVersion:	4.9
+Contact:	Craig Gallek <kraig@xxxxxxxxxx>
+Description:	When interrupt translation domains are used, this file contains
+		the underlying hardware IRQ number used for this Linux IRQ.
+
+What:		/sys/kernel/irq/<irq>/name
+Date:		September 2016
+KernelVersion:	4.9
+Contact:	Craig Gallek <kraig@xxxxxxxxxx>
+Description:	Human-readable flow handler name as defined by the device
+		driver.
+
+What:		/sys/kernel/irq/<irq>/per_cpu_count
+Date:		September 2016
+KernelVersion:	4.9
+Contact:	Craig Gallek <kraig@xxxxxxxxxx>
+Description:	The number of times the interrupt has fired since boot.  This
+		is a comma-separated list of counters; one per online CPU in
+		CPU id order.
+
+What:		/sys/kernel/irq/<irq>/type
+Date:		September 2016
+KernelVersion:	4.9
+Contact:	Craig Gallek <kraig@xxxxxxxxxx>
+Description:	The type of the interrupt.  Either the string 'level' or 'edge'.
diff --git a/include/linux/irqdesc.h b/include/linux/irqdesc.h
index b51beebf9804..aa41d39803b2 100644
--- a/include/linux/irqdesc.h
+++ b/include/linux/irqdesc.h
@@ -2,6 +2,7 @@
 #define _LINUX_IRQDESC_H
 
 #include <linux/rcupdate.h>
+#include <linux/kobject.h>
 
 /*
  * Core internal functions to deal with irq descriptors
@@ -45,6 +46,7 @@ struct pt_regs;
  * @rcu:		rcu head for delayed free
  * @dir:		/proc/irq/ procfs entry
  * @name:		flow handler name for /proc/interrupts output
+ * @kobj:		kobject used to represent this struct in sysfs
  */
 struct irq_desc {
 	struct irq_common_data	irq_common_data;
@@ -92,6 +94,7 @@ struct irq_desc {
 	int			parent_irq;
 	struct module		*owner;
 	const char		*name;
+	struct kobject		kobj;
 } ____cacheline_internodealigned_in_smp;
 
 #ifdef CONFIG_SPARSE_IRQ
diff --git a/kernel/irq/irqdesc.c b/kernel/irq/irqdesc.c
index a623b44f2d4b..2db12c4822f5 100644
--- a/kernel/irq/irqdesc.c
+++ b/kernel/irq/irqdesc.c
@@ -15,6 +15,7 @@
 #include <linux/radix-tree.h>
 #include <linux/bitmap.h>
 #include <linux/irqdomain.h>
+#include <linux/sysfs.h>
 
 #include "internals.h"
 
@@ -121,6 +122,154 @@ EXPORT_SYMBOL_GPL(nr_irqs);
 static DEFINE_MUTEX(sparse_irq_lock);
 static DECLARE_BITMAP(allocated_irqs, IRQ_BITMAP_BITS);
 
+static void irq_kobj_release(struct kobject *kobj);
+
+#ifdef CONFIG_SYSFS
+static struct kobject *irq_kobj_base;
+
+#define IRQ_ATTR_RO(_name) \
+static struct kobj_attribute _name##_attr = __ATTR_RO(_name)
+
+static ssize_t per_cpu_count_show(struct kobject *kobj,
+				  struct kobj_attribute *attr, char *buf)
+{
+	struct irq_desc *desc = container_of(kobj, struct irq_desc, kobj);
+	int cpu, irq = desc->irq_data.irq;
+	ssize_t ret = 0;
+	char *p = "";
+
+	for_each_online_cpu(cpu) {
+		unsigned int c = kstat_irqs_cpu(irq, cpu);
+
+		ret += scnprintf(buf + ret, PAGE_SIZE - ret, "%s%u", p, c);
+		p = ",";
+	}
+
+	ret += scnprintf(buf + ret, PAGE_SIZE - ret, "\n");
+	return ret;
+}
+IRQ_ATTR_RO(per_cpu_count);
+
+static ssize_t chip_name_show(struct kobject *kobj,
+			      struct kobj_attribute *attr, char *buf)
+{
+	struct irq_desc *desc = container_of(kobj, struct irq_desc, kobj);
+	ssize_t ret = 0;
+
+	raw_spin_lock_irq(&desc->lock);
+	if (desc->irq_data.chip && desc->irq_data.chip->name) {
+		ret = scnprintf(buf, PAGE_SIZE, "%s\n",
+				desc->irq_data.chip->name);
+	}
+	raw_spin_unlock_irq(&desc->lock);
+
+	return ret;
+}
+IRQ_ATTR_RO(chip_name);
+
+static ssize_t hwirq_show(struct kobject *kobj,
+			  struct kobj_attribute *attr, char *buf)
+{
+	struct irq_desc *desc = container_of(kobj, struct irq_desc, kobj);
+	ssize_t ret = 0;
+
+	raw_spin_lock_irq(&desc->lock);
+	if (desc->irq_data.domain)
+		ret = sprintf(buf, "%d\n", (int)desc->irq_data.hwirq);
+	raw_spin_unlock_irq(&desc->lock);
+
+	return ret;
+}
+IRQ_ATTR_RO(hwirq);
+
+static ssize_t type_show(struct kobject *kobj,
+			 struct kobj_attribute *attr, char *buf)
+{
+	struct irq_desc *desc = container_of(kobj, struct irq_desc, kobj);
+	ssize_t ret = 0;
+
+	raw_spin_lock_irq(&desc->lock);
+	ret = sprintf(buf, "%s\n",
+		      irqd_is_level_type(&desc->irq_data) ? "level" : "edge");
+	raw_spin_unlock_irq(&desc->lock);
+
+	return ret;
+
+}
+IRQ_ATTR_RO(type);
+
+static ssize_t name_show(struct kobject *kobj,
+			 struct kobj_attribute *attr, char *buf)
+{
+	struct irq_desc *desc = container_of(kobj, struct irq_desc, kobj);
+	ssize_t ret = 0;
+
+	raw_spin_lock_irq(&desc->lock);
+	if (desc->name)
+		ret = scnprintf(buf, PAGE_SIZE, "%s\n", desc->name);
+	raw_spin_unlock_irq(&desc->lock);
+
+	return ret;
+}
+IRQ_ATTR_RO(name);
+
+static ssize_t actions_show(struct kobject *kobj,
+			    struct kobj_attribute *attr, char *buf)
+{
+	struct irq_desc *desc = container_of(kobj, struct irq_desc, kobj);
+	struct irqaction *action;
+	ssize_t ret = 0;
+	char *p = "";
+
+	raw_spin_lock_irq(&desc->lock);
+	for (action = desc->action; action != NULL; action = action->next) {
+		ret += scnprintf(buf + ret, PAGE_SIZE - ret, "%s%s",
+				 p, action->name);
+		p = ",";
+	}
+	raw_spin_unlock_irq(&desc->lock);
+
+	if (ret)
+		ret += scnprintf(buf + ret, PAGE_SIZE - ret, "\n");
+
+	return ret;
+}
+IRQ_ATTR_RO(actions);
+
+static struct attribute *irq_attrs[] = {
+	&per_cpu_count_attr.attr,
+	&chip_name_attr.attr,
+	&hwirq_attr.attr,
+	&type_attr.attr,
+	&name_attr.attr,
+	&actions_attr.attr,
+	NULL
+};
+
+static struct kobj_type irq_kobj_type = {
+	.release	= irq_kobj_release,
+	.sysfs_ops	= &kobj_sysfs_ops,
+	.default_attrs	= irq_attrs,
+};
+
+static void irq_sysfs_add(int irq, struct irq_desc *desc)
+{
+	if (irq_kobj_base) {
+		if (kobject_add(&desc->kobj, irq_kobj_base, "%d", irq))
+			pr_warn("Failed to add kobject for irq %d\n", irq);
+	}
+}
+
+#else /* !CONFIG_SYSFS */
+
+static struct kobj_type irq_kobj_type = {
+	.release	= irq_kobj_release,
+};
+
+static void irq_sysfs_add(int irq, struct irq_desc *desc) {}
+
+#endif /* CONFIG_SYSFS */
+
 #ifdef CONFIG_SPARSE_IRQ
 
 static RADIX_TREE(irq_desc_tree, GFP_KERNEL);
@@ -187,6 +336,7 @@ static struct irq_desc *alloc_desc(int irq, int node, unsigned int flags,
 
 	desc_set_defaults(irq, desc, node, affinity, owner);
 	irqd_set(&desc->irq_data, flags);
+	kobject_init(&desc->kobj, &irq_kobj_type);
 
 	return desc;
 
@@ -197,20 +347,28 @@ err_desc:
 	return NULL;
 }
 
-static void delayed_free_desc(struct rcu_head *rhp)
+static void irq_kobj_release(struct kobject *kobj)
 {
-	struct irq_desc *desc = container_of(rhp, struct irq_desc, rcu);
+	struct irq_desc *desc = container_of(kobj, struct irq_desc, kobj);
 
 	free_masks(desc);
 	free_percpu(desc->kstat_irqs);
 	kfree(desc);
 }
 
+static void delayed_free_desc(struct rcu_head *rhp)
+{
+	struct irq_desc *desc = container_of(rhp, struct irq_desc, rcu);
+
+	kobject_put(&desc->kobj);
+}
+
 static void free_desc(unsigned int irq)
 {
 	struct irq_desc *desc = irq_to_desc(irq);
 
 	unregister_irq_proc(irq, desc);
+	kobject_del(&desc->kobj);
 
 	/*
 	 * sparse_irq_lock protects also show_interrupts() and
@@ -261,6 +419,7 @@ static int alloc_descs(unsigned int start, unsigned int cnt, int node,
 			goto err;
 		mutex_lock(&sparse_irq_lock);
 		irq_insert_desc(start + i, desc);
+		irq_sysfs_add(start + i, desc);
 		mutex_unlock(&sparse_irq_lock);
 	}
 	return start;
@@ -339,6 +498,7 @@ int __init early_irq_init(void)
 		raw_spin_lock_init(&desc[i].lock);
 		lockdep_set_class(&desc[i].lock, &irq_desc_lock_class);
 		desc_set_defaults(i, &desc[i], node, NULL, NULL);
+		kobject_init(&desc[i].kobj, &irq_kobj_type);
 	}
 	return arch_early_irq_init();
 }
@@ -349,11 +509,15 @@ struct irq_desc *irq_to_desc(unsigned int irq)
 }
 EXPORT_SYMBOL(irq_to_desc);
 
+/* Statically allocated irq_desc is never deallocated */
+static void irq_kobj_release(struct kobject *kobj) {}
+
 static void free_desc(unsigned int irq)
 {
 	struct irq_desc *desc = irq_to_desc(irq);
 	unsigned long flags;
 
+	kobject_del(&desc->kobj);
 	raw_spin_lock_irqsave(&desc->lock, flags);
 	desc_set_defaults(irq, desc, irq_desc_get_node(desc), NULL, NULL);
 	raw_spin_unlock_irqrestore(&desc->lock, flags);
@@ -369,6 +533,7 @@ static inline int alloc_descs(unsigned int start, unsigned int cnt, int node,
 		struct irq_desc *desc = irq_to_desc(start + i);
 
 		desc->owner = owner;
+		irq_sysfs_add(start + i, desc);
 	}
 	return start;
 }
@@ -730,3 +895,23 @@ unsigned int kstat_irqs_usr(unsigned int irq)
 	irq_unlock_sparse();
 	return sum;
 }
+
+#ifdef CONFIG_SYSFS
+static int __init irq_sysfs_init(void)
+{
+	struct irq_desc *desc;
+	int irq;
+
+	irq_kobj_base = kobject_create_and_add("irq", kernel_kobj);
+	if (!irq_kobj_base)
+		return -ENOMEM;
+
+	irq_lock_sparse();
+	for_each_irq_desc(irq, desc)
+		irq_sysfs_add(irq, desc);
+	irq_unlock_sparse();
+
+	return 0;
+}
+postcore_initcall(irq_sysfs_init);
+#endif /* CONFIG_SYSFS */
-- 
2.8.0.rc3.226.g39d4020