LXR linux/drivers/hwtracing/stm/ftrace.c

   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>");
  82