1// SPDX-License-Identifier: GPL-2.0
 2/*
 3 * Simple kernel driver to link kernel Ftrace and an STM device
 4 * Copyright (c) 2016, Linaro Ltd.
 5 *
 6 * STM Ftrace will be registered as a trace_export.
 7 */
 8
 9#include <linux/module.h>
10#include <linux/stm.h>
11#include <linux/trace.h>
12
13#define STM_FTRACE_NR_CHANNELS 1
14#define STM_FTRACE_CHAN 0
15
16static int stm_ftrace_link(struct stm_source_data *data);
17static void stm_ftrace_unlink(struct stm_source_data *data);
18
19static struct stm_ftrace {
20	struct stm_source_data	data;
21	struct trace_export	ftrace;
22} stm_ftrace = {
23	.data	= {
24		.name		= "ftrace",
25		.nr_chans	= STM_FTRACE_NR_CHANNELS,
26		.link		= stm_ftrace_link,
27		.unlink		= stm_ftrace_unlink,
28	},
29};
30
31/**
32 * stm_ftrace_write() - write data to STM via 'stm_ftrace' source
33 * @buf:	buffer containing the data packet
34 * @len:	length of the data packet
35 */
36static void notrace
37stm_ftrace_write(struct trace_export *export, const void *buf, unsigned int len)
38{
39	struct stm_ftrace *stm = container_of(export, struct stm_ftrace, ftrace);
40
41	stm_source_write(&stm->data, STM_FTRACE_CHAN, buf, len);
42}
43
44static int stm_ftrace_link(struct stm_source_data *data)
45{
46	struct stm_ftrace *sf = container_of(data, struct stm_ftrace, data);
47
48	sf->ftrace.write = stm_ftrace_write;
49
50	return register_ftrace_export(&sf->ftrace);
51}
52
53static void stm_ftrace_unlink(struct stm_source_data *data)
54{
55	struct stm_ftrace *sf = container_of(data, struct stm_ftrace, data);
56
57	unregister_ftrace_export(&sf->ftrace);
58}
59
60static int __init stm_ftrace_init(void)
61{
62	int ret;
63
64	ret = stm_source_register_device(NULL, &stm_ftrace.data);
65	if (ret)
66		pr_err("Failed to register stm_source - ftrace.\n");
67
68	return ret;
69}
70
71static void __exit stm_ftrace_exit(void)
72{
73	stm_source_unregister_device(&stm_ftrace.data);
74}
75
76module_init(stm_ftrace_init);
77module_exit(stm_ftrace_exit);
78
79MODULE_LICENSE("GPL v2");
80MODULE_DESCRIPTION("stm_ftrace driver");
81MODULE_AUTHOR("Chunyan Zhang <zhang.chunyan@linaro.org>");