1/*
  2 * Simple heartbeat STM source driver
  3 * Copyright (c) 2016, Intel Corporation.
  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 * Heartbeat STM source will send repetitive messages over STM devices to a
 15 * trace host.
 16 */
 17
 18#include <linux/kernel.h>
 19#include <linux/module.h>
 20#include <linux/hrtimer.h>
 21#include <linux/slab.h>
 22#include <linux/stm.h>
 23
 24#define STM_HEARTBEAT_MAX	32
 25
 26static int nr_devs = 4;
 27static int interval_ms = 10;
 28
 29module_param(nr_devs, int, 0600);
 30module_param(interval_ms, int, 0600);
 31
 32static struct stm_heartbeat {
 33	struct stm_source_data	data;
 34	struct hrtimer		hrtimer;
 35	unsigned int		active;
 36} stm_heartbeat[STM_HEARTBEAT_MAX];
 37
 38static unsigned int nr_instances;
 39
 40static const char str[] = "heartbeat stm source driver is here to serve you";
 41
 42static enum hrtimer_restart stm_heartbeat_hrtimer_handler(struct hrtimer *hr)
 43{
 44	struct stm_heartbeat *heartbeat = container_of(hr, struct stm_heartbeat,
 45						       hrtimer);
 46
 47	stm_source_write(&heartbeat->data, 0, str, sizeof str);
 48	if (heartbeat->active)
 49		hrtimer_forward_now(hr, ms_to_ktime(interval_ms));
 50
 51	return heartbeat->active ? HRTIMER_RESTART : HRTIMER_NORESTART;
 52}
 53
 54static int stm_heartbeat_link(struct stm_source_data *data)
 55{
 56	struct stm_heartbeat *heartbeat =
 57		container_of(data, struct stm_heartbeat, data);
 58
 59	heartbeat->active = 1;
 60	hrtimer_start(&heartbeat->hrtimer, ms_to_ktime(interval_ms),
 61		      HRTIMER_MODE_ABS);
 62
 63	return 0;
 64}
 65
 66static void stm_heartbeat_unlink(struct stm_source_data *data)
 67{
 68	struct stm_heartbeat *heartbeat =
 69		container_of(data, struct stm_heartbeat, data);
 70
 71	heartbeat->active = 0;
 72	hrtimer_cancel(&heartbeat->hrtimer);
 73}
 74
 75static int stm_heartbeat_init(void)
 76{
 77	int i, ret = -ENOMEM, __nr_instances = ACCESS_ONCE(nr_devs);
 78
 79	if (__nr_instances < 0 || __nr_instances > STM_HEARTBEAT_MAX)
 80		return -EINVAL;
 81
 82	for (i = 0; i < __nr_instances; i++) {
 83		stm_heartbeat[i].data.name =
 84			kasprintf(GFP_KERNEL, "heartbeat.%d", i);
 85		if (!stm_heartbeat[i].data.name)
 86			goto fail_unregister;
 87
 88		stm_heartbeat[i].data.nr_chans	= 1;
 89		stm_heartbeat[i].data.link		= stm_heartbeat_link;
 90		stm_heartbeat[i].data.unlink	= stm_heartbeat_unlink;
 91		hrtimer_init(&stm_heartbeat[i].hrtimer, CLOCK_MONOTONIC,
 92			     HRTIMER_MODE_ABS);
 93		stm_heartbeat[i].hrtimer.function =
 94			stm_heartbeat_hrtimer_handler;
 95
 96		ret = stm_source_register_device(NULL, &stm_heartbeat[i].data);
 97		if (ret)
 98			goto fail_free;
 99	}
100
101	nr_instances = __nr_instances;
102
103	return 0;
104
105fail_unregister:
106	for (i--; i >= 0; i--) {
107		stm_source_unregister_device(&stm_heartbeat[i].data);
108fail_free:
109		kfree(stm_heartbeat[i].data.name);
110	}
111
112	return ret;
113}
114
115static void stm_heartbeat_exit(void)
116{
117	int i;
118
119	for (i = 0; i < nr_instances; i++) {
120		stm_source_unregister_device(&stm_heartbeat[i].data);
121		kfree(stm_heartbeat[i].data.name);
122	}
123}
124
125module_init(stm_heartbeat_init);
126module_exit(stm_heartbeat_exit);
127
128MODULE_LICENSE("GPL v2");
129MODULE_DESCRIPTION("stm_heartbeat driver");
130MODULE_AUTHOR("Alexander Shishkin <alexander.shishkin@linux.intel.com>");