1/*
 2 * Simple kernel driver to link kernel Ftrace and an STM device
 3 * Copyright (c) 2016, Linaro Ltd.
 4 *
 5 * This program is free software; you can redistribute it and/or modify it
 6 * under the terms and conditions of the GNU General Public License,
 7 * version 2, as published by the Free Software Foundation.
 8 *
 9 * This program is distributed in the hope it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
12 * more details.
13 *
14 * STM Ftrace will be registered as a trace_export.
15 */
16
17#include <linux/module.h>
18#include <linux/stm.h>
19#include <linux/trace.h>
20
21#define STM_FTRACE_NR_CHANNELS 1
22#define STM_FTRACE_CHAN 0
23
24static int stm_ftrace_link(struct stm_source_data *data);
25static void stm_ftrace_unlink(struct stm_source_data *data);
26
27static struct stm_ftrace {
28	struct stm_source_data	data;
29	struct trace_export	ftrace;
30} stm_ftrace = {
31	.data	= {
32		.name		= "ftrace",
33		.nr_chans	= STM_FTRACE_NR_CHANNELS,
34		.link		= stm_ftrace_link,
35		.unlink		= stm_ftrace_unlink,
36	},
37};
38
39/**
40 * stm_ftrace_write() - write data to STM via 'stm_ftrace' source
41 * @buf:	buffer containing the data packet
42 * @len:	length of the data packet
43 */
44static void notrace
45stm_ftrace_write(const void *buf, unsigned int len)
46{
47	stm_source_write(&stm_ftrace.data, STM_FTRACE_CHAN, buf, len);
48}
49
50static int stm_ftrace_link(struct stm_source_data *data)
51{
52	struct stm_ftrace *sf = container_of(data, struct stm_ftrace, data);
53
54	sf->ftrace.write = stm_ftrace_write;
55
56	return register_ftrace_export(&sf->ftrace);
57}
58
59static void stm_ftrace_unlink(struct stm_source_data *data)
60{
61	struct stm_ftrace *sf = container_of(data, struct stm_ftrace, data);
62
63	unregister_ftrace_export(&sf->ftrace);
64}
65
66static int __init stm_ftrace_init(void)
67{
68	int ret;
69
70	ret = stm_source_register_device(NULL, &stm_ftrace.data);
71	if (ret)
72		pr_err("Failed to register stm_source - ftrace.\n");
73
74	return ret;
75}
76
77static void __exit stm_ftrace_exit(void)
78{
79	stm_source_unregister_device(&stm_ftrace.data);
80}
81
82module_init(stm_ftrace_init);
83module_exit(stm_ftrace_exit);
84
85MODULE_LICENSE("GPL v2");
86MODULE_DESCRIPTION("stm_ftrace driver");
87MODULE_AUTHOR("Chunyan Zhang <zhang.chunyan@linaro.org>");