linux-kernel - [PATCH] kernel: trace: pass export pointer as argument to ->write()

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Message-Id: <20170517080554.1915-1-felipe.balbi@linux.intel.com>
Date:   Wed, 17 May 2017 11:05:54 +0300
From:   Felipe Balbi <felipe.balbi@...ux.intel.com>
To:     Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>
Cc:     linux-kernel@...r.kernel.org,
        Chunyan Zhang <zhang.chunyan@...aro.org>,
        Felipe Balbi <felipe.balbi@...ux.intel.com>
Subject: [PATCH] kernel: trace: pass export pointer as argument to ->write()

That way, users don't need to keep a global static pointer and can
rely on container_of() to fetch their own structure.

Signed-off-by: Felipe Balbi <felipe.balbi@...ux.intel.com>
---

I'm working on exposing this data over a USB peripheral controller and
I really can't have a global pointer there.

 drivers/hwtracing/stm/ftrace.c | 6 ++++--
 include/linux/trace.h          | 2 +-
 kernel/trace/trace.c           | 2 +-
 3 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/hwtracing/stm/ftrace.c b/drivers/hwtracing/stm/ftrace.c
index bd126a7c6da2..371b8333d9ae 100644
--- a/drivers/hwtracing/stm/ftrace.c
+++ b/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)
diff --git a/include/linux/trace.h b/include/linux/trace.h
index 9330a58e2651..477aed6f0caa 100644
--- a/include/linux/trace.h
+++ b/include/linux/trace.h
@@ -17,7 +17,7 @@
  */
 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);
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index c4536c449021..6a96652a3b0f 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -2317,7 +2317,7 @@ 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);
-- 
2.11.0.295.gd7dffce1ce