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Subject[RFC][PATCH 04/11] ftrace: provide an id file for each event
Since not every event has a format file to read the id from, expose it
explicitly in a separate file.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
kernel/trace/trace_events.c | 36 ++++++++++++++++++++++++++++++++++++
1 file changed, 36 insertions(+)
Index: linux-2.6/kernel/trace/trace_events.c
===================================================================
--- linux-2.6.orig/kernel/trace/trace_events.c
+++ linux-2.6/kernel/trace/trace_events.c
@@ -414,6 +414,29 @@ event_format_read(struct file *filp, cha
return r;
}

+static ssize_t
+event_id_read(struct file *filp, char __user *ubuf, size_t cnt, loff_t *ppos)
+{
+ struct ftrace_event_call *call = filp->private_data;
+ struct trace_seq *s;
+ int r;
+
+ if (*ppos)
+ return 0;
+
+ s = kmalloc(sizeof(*s), GFP_KERNEL);
+ if (!s)
+ return -ENOMEM;
+
+ trace_seq_init(s);
+ trace_seq_printf(s, "%d\n", call->id);
+
+ r = simple_read_from_buffer(ubuf, cnt, ppos,
+ s->buffer, s->len);
+ kfree(s);
+ return r;
+}
+
static const struct seq_operations show_event_seq_ops = {
.start = t_start,
.next = t_next,
@@ -454,6 +477,11 @@ static const struct file_operations ftra
.read = event_format_read,
};

+static const struct file_operations ftrace_event_id_fops = {
+ .open = tracing_open_generic,
+ .read = event_id_read,
+};
+
static struct dentry *event_trace_events_dir(void)
{
static struct dentry *d_tracer;
@@ -552,6 +580,14 @@ event_create_dir(struct ftrace_event_cal
"'%s/enable' entry\n", call->name);
}

+ if (call->id) {
+ entry = debugfs_create_file("id", 0444, call->dir, call,
+ &ftrace_event_id_fops);
+ if (!entry)
+ pr_warning("Could not create debugfs '%s/id' entry\n",
+ call->name);
+ }
+
/* A trace may not want to export its format */
if (!call->show_format)
return 0;
--



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