xref: /linux/drivers/hwtracing/stm/ftrace.c (revision 3ad0876554cafa368f574d4d408468510543e9ff)
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 
24 static int stm_ftrace_link(struct stm_source_data *data);
25 static void stm_ftrace_unlink(struct stm_source_data *data);
26 
27 static 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  */
44 static void notrace
45 stm_ftrace_write(struct trace_export *export, const void *buf, unsigned int len)
46 {
47 	struct stm_ftrace *stm = container_of(export, struct stm_ftrace, ftrace);
48 
49 	stm_source_write(&stm->data, STM_FTRACE_CHAN, buf, len);
50 }
51 
52 static int stm_ftrace_link(struct stm_source_data *data)
53 {
54 	struct stm_ftrace *sf = container_of(data, struct stm_ftrace, data);
55 
56 	sf->ftrace.write = stm_ftrace_write;
57 
58 	return register_ftrace_export(&sf->ftrace);
59 }
60 
61 static void stm_ftrace_unlink(struct stm_source_data *data)
62 {
63 	struct stm_ftrace *sf = container_of(data, struct stm_ftrace, data);
64 
65 	unregister_ftrace_export(&sf->ftrace);
66 }
67 
68 static int __init stm_ftrace_init(void)
69 {
70 	int ret;
71 
72 	ret = stm_source_register_device(NULL, &stm_ftrace.data);
73 	if (ret)
74 		pr_err("Failed to register stm_source - ftrace.\n");
75 
76 	return ret;
77 }
78 
79 static void __exit stm_ftrace_exit(void)
80 {
81 	stm_source_unregister_device(&stm_ftrace.data);
82 }
83 
84 module_init(stm_ftrace_init);
85 module_exit(stm_ftrace_exit);
86 
87 MODULE_LICENSE("GPL v2");
88 MODULE_DESCRIPTION("stm_ftrace driver");
89 MODULE_AUTHOR("Chunyan Zhang <zhang.chunyan@linaro.org>");
90