heartbeat.c

  1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * Simple heartbeat STM source driver
  4 * Copyright (c) 2016, Intel Corporation.
  5 *
  6 * Heartbeat STM source will send repetitive messages over STM devices to a
  7 * trace host.
  8 */
  9
 10#include <linux/kernel.h>
 11#include <linux/module.h>
 12#include <linux/hrtimer.h>
 13#include <linux/slab.h>
 14#include <linux/stm.h>
 15
 16#define STM_HEARTBEAT_MAX	32
 17
 18static int nr_devs = 4;
 19static int interval_ms = 10;
 20
 21module_param(nr_devs, int, 0400);
 22module_param(interval_ms, int, 0600);
 23
 24static struct stm_heartbeat {
 25	struct stm_source_data	data;
 26	struct hrtimer		hrtimer;
 27	unsigned int		active;
 28} stm_heartbeat[STM_HEARTBEAT_MAX];
 29
 30static const char str[] = "heartbeat stm source driver is here to serve you";
 31
 32static enum hrtimer_restart stm_heartbeat_hrtimer_handler(struct hrtimer *hr)
 33{
 34	struct stm_heartbeat *heartbeat = container_of(hr, struct stm_heartbeat,
 35						       hrtimer);
 36
 37	stm_source_write(&heartbeat->data, 0, str, sizeof str);
 38	if (heartbeat->active)
 39		hrtimer_forward_now(hr, ms_to_ktime(interval_ms));
 40
 41	return heartbeat->active ? HRTIMER_RESTART : HRTIMER_NORESTART;
 42}
 43
 44static int stm_heartbeat_link(struct stm_source_data *data)
 45{
 46	struct stm_heartbeat *heartbeat =
 47		container_of(data, struct stm_heartbeat, data);
 48
 49	heartbeat->active = 1;
 50	hrtimer_start(&heartbeat->hrtimer, ms_to_ktime(interval_ms),
 51		      HRTIMER_MODE_ABS);
 52
 53	return 0;
 54}
 55
 56static void stm_heartbeat_unlink(struct stm_source_data *data)
 57{
 58	struct stm_heartbeat *heartbeat =
 59		container_of(data, struct stm_heartbeat, data);
 60
 61	heartbeat->active = 0;
 62	hrtimer_cancel(&heartbeat->hrtimer);
 63}
 64
 65static int stm_heartbeat_init(void)
 66{
 67	int i, ret;
 68
 69	if (nr_devs < 0 || nr_devs > STM_HEARTBEAT_MAX)
 70		return -EINVAL;
 71
 72	for (i = 0; i < nr_devs; i++) {
 73		stm_heartbeat[i].data.name =
 74			kasprintf(GFP_KERNEL, "heartbeat.%d", i);
 75		if (!stm_heartbeat[i].data.name) {
 76			ret = -ENOMEM;
 77			goto fail_unregister;
 78		}
 79
 80		stm_heartbeat[i].data.nr_chans	= 1;
 81		stm_heartbeat[i].data.type	= STM_USER;
 82		stm_heartbeat[i].data.link	= stm_heartbeat_link;
 83		stm_heartbeat[i].data.unlink	= stm_heartbeat_unlink;
 84		hrtimer_setup(&stm_heartbeat[i].hrtimer, stm_heartbeat_hrtimer_handler,
 85			      CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
 86
 87		ret = stm_source_register_device(NULL, &stm_heartbeat[i].data);
 88		if (ret)
 89			goto fail_free;
 90	}
 91
 92	return 0;
 93
 94fail_unregister:
 95	for (i--; i >= 0; i--) {
 96		stm_source_unregister_device(&stm_heartbeat[i].data);
 97fail_free:
 98		kfree(stm_heartbeat[i].data.name);
 99	}
100
101	return ret;
102}
103
104static void stm_heartbeat_exit(void)
105{
106	int i;
107
108	for (i = 0; i < nr_devs; i++) {
109		stm_source_unregister_device(&stm_heartbeat[i].data);
110		kfree(stm_heartbeat[i].data.name);
111	}
112}
113
114module_init(stm_heartbeat_init);
115module_exit(stm_heartbeat_exit);
116
117MODULE_LICENSE("GPL v2");
118MODULE_DESCRIPTION("stm_heartbeat driver");
119MODULE_AUTHOR("Alexander Shishkin <alexander.shishkin@linux.intel.com>");