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