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    SubjectRe: [PATCH v2 1/6] perf: Add interface to add general events to sysfs
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    On Mon, 2011-07-18 at 21:34 +0800, Peter Zijlstra wrote:
    >
    > Also, I would prefer an interface like:
    >
    > int perf_pmu_add_event(struct pmu *pmu, const char *name, u64 config)
    > {
    > }
    >
    > which would create the events directory if not already present and
    > allocate and add a pmu_sysfs_event thingy.

    It's strange that I didn't find a way to check if a directory is present
    in sysfs. Any hint?

    So I proceeded with below code.

    diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
    index 14337a3..6db73d0 100644
    --- a/include/linux/perf_event.h
    +++ b/include/linux/perf_event.h
    @@ -611,6 +611,7 @@ struct pmu {
    struct list_head entry;

    struct device *dev;
    + struct kobject *events;
    char *name;
    int type;
    diff --git a/kernel/events/core.c b/kernel/events/core.c
    index 3870c106..080d684 100644
    --- a/kernel/events/core.c
    +++ b/kernel/events/core.c
    @@ -7081,3 +7081,35 @@ fail:
    kfree(attr_group);
    kfree(all_attrs);
    }
    +
    +#define NAME_LEN 64
    +
    +int perf_pmu_add_event(struct pmu *pmu, const char *name, u64 config)
    +{
    + struct kobject *events = pmu->events;
    + struct pmu_event *event;
    + struct kobj_attribute *event_attr;
    +
    + if (!pmu_bus_running)
    + return -EINVAL;
    +
    + if (!events) {
    + events = kobject_create_and_add("events", &pmu->dev->kobj);
    + if (!unlikely(events))
    + return -ENOMEM;
    + }
    +
    + event = kzalloc(sizeof(*event), GFP_KERNEL);
    + if (!event)
    + return -ENOMEM;
    +
    + strncpy(event->name, name, NAME_LEN);
    + event->config = config;
    + event_attr = &event->attr;
    + sysfs_attr_init(&event_attr->attr);
    + event_attr->attr.name = event->name;
    + event_attr->attr.mode = 0444;
    + event_attr->show = pmu_event_show;
    +
    + return sysfs_create_file(events, &event_attr->attr);
    +}




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