perf: Sysfs enumeration

Simple sysfs emumeration of the PMUs.

Use a "event_source" bus, and add PMU devices using their name.

Each PMU device has a type attribute which contrains the value needed
for perf_event_attr::type to identify this PMU.

This is the minimal stub needed to start using this interface,
we'll consider extending the sysfs usage later.

Cc: Kay Sievers <kay.sievers@vrfy.org>
Cc: Greg KH <gregkh@suse.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <20101117222056.316982569@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

2 files changed, 95 insertions, 1 deletions

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 21206d27466b..dda5b0a3ff60 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -588,6 +588,7 @@ struct perf_event;
 struct pmu {
         struct list_head                entry;
 
+        struct device                   *dev;
         char                            *name;
         int                             type;
 
diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index 8f09bc877a30..11847bf1e8cc 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -24,6 +24,7 @@
 #include <linux/ptrace.h>
 #include <linux/reboot.h>
 #include <linux/vmstat.h>
+#include <linux/device.h>
 #include <linux/vmalloc.h>
 #include <linux/hardirq.h>
 #include <linux/rculist.h>
@@ -5308,6 +5309,58 @@ out:
 }
 static struct idr pmu_idr;
 
+static ssize_t
+type_show(struct device *dev, struct device_attribute *attr, char *page)
+{
+        struct pmu *pmu = dev_get_drvdata(dev);
+
+        return snprintf(page, PAGE_SIZE-1, "%d\n", pmu->type);
+}
+
+static struct device_attribute pmu_dev_attrs[] = {
+       __ATTR_RO(type),
+       __ATTR_NULL,
+};
+
+static int pmu_bus_running;
+static struct bus_type pmu_bus = {
+        .name           = "event_source",
+        .dev_attrs      = pmu_dev_attrs,
+};
+
+static void pmu_dev_release(struct device *dev)
+{
+        kfree(dev);
+}
+
+static int pmu_dev_alloc(struct pmu *pmu)
+{
+        int ret = -ENOMEM;
+
+        pmu->dev = kzalloc(sizeof(struct device), GFP_KERNEL);
+        if (!pmu->dev)
+                goto out;
+
+        device_initialize(pmu->dev);
+        ret = dev_set_name(pmu->dev, "%s", pmu->name);
+        if (ret)
+                goto free_dev;
+
+        dev_set_drvdata(pmu->dev, pmu);
+        pmu->dev->bus = &pmu_bus;
+        pmu->dev->release = pmu_dev_release;
+        ret = device_add(pmu->dev);
+        if (ret)
+                goto free_dev;
+
+out:
+        return ret;
+
+free_dev:
+        put_device(pmu->dev);
+        goto out;
+}
+
 int perf_pmu_register(struct pmu *pmu, char *name, int type)
 {
         int cpu, ret;
@@ -5336,6 +5389,12 @@ int perf_pmu_register(struct pmu *pmu, char *name, int type)
         }
         pmu->type = type;
 
+        if (pmu_bus_running) {
+                ret = pmu_dev_alloc(pmu);
+                if (ret)
+                        goto free_idr;
+        }
+
 skip_type:
         pmu->pmu_cpu_context = find_pmu_context(pmu->task_ctx_nr);
         if (pmu->pmu_cpu_context)
@@ -5343,7 +5402,7 @@ skip_type:
 
         pmu->pmu_cpu_context = alloc_percpu(struct perf_cpu_context);
         if (!pmu->pmu_cpu_context)
-                goto free_ird;
+                goto free_dev;
 
         for_each_possible_cpu(cpu) {
                 struct perf_cpu_context *cpuctx;
@@ -5387,6 +5446,10 @@ unlock:
 
         return ret;
 
+free_dev:
+        device_del(pmu->dev);
+        put_device(pmu->dev);
+
 free_idr:
         if (pmu->type >= PERF_TYPE_MAX)
                 idr_remove(&pmu_idr, pmu->type);
@@ -5412,6 +5475,8 @@ void perf_pmu_unregister(struct pmu *pmu)
         free_percpu(pmu->pmu_disable_count);
         if (pmu->type >= PERF_TYPE_MAX)
                 idr_remove(&pmu_idr, pmu->type);
+        device_del(pmu->dev);
+        put_device(pmu->dev);
         free_pmu_context(pmu);
 }
 
@@ -6603,3 +6668,31 @@ void __init perf_event_init(void)
         ret = init_hw_breakpoint();
         WARN(ret, "hw_breakpoint initialization failed with: %d", ret);
 }
+
+static int __init perf_event_sysfs_init(void)
+{
+        struct pmu *pmu;
+        int ret;
+
+        mutex_lock(&pmus_lock);
+
+        ret = bus_register(&pmu_bus);
+        if (ret)
+                goto unlock;
+
+        list_for_each_entry(pmu, &pmus, entry) {
+                if (!pmu->name || pmu->type < 0)
+                        continue;
+
+                ret = pmu_dev_alloc(pmu);
+                WARN(ret, "Failed to register pmu: %s, reason %d\n", pmu->name, ret);
+        }
+        pmu_bus_running = 1;
+        ret = 0;
+
+unlock:
+        mutex_unlock(&pmus_lock);
+
+        return ret;
+}
+device_initcall(perf_event_sysfs_init);