tracing: Pass export pointer as argument to ->write()

By passing an export descriptor to the write function, users don't need to
keep a global static pointer and can rely on container_of() to fetch their
own structure.

Link: http://lkml.kernel.org/r/20170602102025.5140-1-felipe.balbi@linux.intel.com

Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Reviewed-by: Chunyan Zhang <zhang.chunyan@linaro.org>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

drivers/hwtracing/stm/ftrace.c

@@ -42,9 +42,11 @@ static struct stm_ftrace {
  * @len:	length of the data packet
  */
 static void notrace
-stm_ftrace_write(const void *buf, unsigned int len)
+stm_ftrace_write(struct trace_export *export, const void *buf, unsigned int len)
 {
-	stm_source_write(&stm_ftrace.data, STM_FTRACE_CHAN, buf, len);
+	struct stm_ftrace *stm = container_of(export, struct stm_ftrace, ftrace);
+
+	stm_source_write(&stm->data, STM_FTRACE_CHAN, buf, len);
 }
 
 static int stm_ftrace_link(struct stm_source_data *data)

include/linux/trace.h

@@ -18,7 +18,7 @@
  */
 struct trace_export {
 	struct trace_export __rcu	*next;
-	void (*write)(const void *, unsigned int);
+	void (*write)(struct trace_export *, const void *, unsigned int);
 };
 
 int register_ftrace_export(struct trace_export *export);

kernel/trace/trace.c

@@ -2415,7 +2415,7 @@ trace_process_export(struct trace_export *export,
 
 	entry = ring_buffer_event_data(event);
 	size = ring_buffer_event_length(event);
-	export->write(entry, size);
+	export->write(export, entry, size);
 }
 
 static DEFINE_MUTEX(ftrace_export_lock);