drivers/hwtracing/stm/ftrace.c

   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>");