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 18 static int nr_devs = 4; 19 static int interval_ms = 10; 20 21 module_param(nr_devs, int, 0400); 22 module_param(interval_ms, int, 0600); 23 24 static struct stm_heartbeat { 25 struct stm_source_data data; 26 struct hrtimer hrtimer; 27 unsigned int active; 28 } stm_heartbeat[STM_HEARTBEAT_MAX]; 29 30 static const char str[] = "heartbeat stm source driver is here to serve you"; 31 32 static 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 44 static 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 56 static 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 65 static int stm_heartbeat_init(void) 66 { 67 int i, ret = -ENOMEM; 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 goto fail_unregister; 77 78 stm_heartbeat[i].data.nr_chans = 1; 79 stm_heartbeat[i].data.link = stm_heartbeat_link; 80 stm_heartbeat[i].data.unlink = stm_heartbeat_unlink; 81 hrtimer_init(&stm_heartbeat[i].hrtimer, CLOCK_MONOTONIC, 82 HRTIMER_MODE_ABS); 83 stm_heartbeat[i].hrtimer.function = 84 stm_heartbeat_hrtimer_handler; 85 86 ret = stm_source_register_device(NULL, &stm_heartbeat[i].data); 87 if (ret) 88 goto fail_free; 89 } 90 91 return 0; 92 93 fail_unregister: 94 for (i--; i >= 0; i--) { 95 stm_source_unregister_device(&stm_heartbeat[i].data); 96 fail_free: 97 kfree(stm_heartbeat[i].data.name); 98 } 99 100 return ret; 101 } 102 103 static void stm_heartbeat_exit(void) 104 { 105 int i; 106 107 for (i = 0; i < nr_devs; i++) { 108 stm_source_unregister_device(&stm_heartbeat[i].data); 109 kfree(stm_heartbeat[i].data.name); 110 } 111 } 112 113 module_init(stm_heartbeat_init); 114 module_exit(stm_heartbeat_exit); 115 116 MODULE_LICENSE("GPL v2"); 117 MODULE_DESCRIPTION("stm_heartbeat driver"); 118 MODULE_AUTHOR("Alexander Shishkin <alexander.shishkin@linux.intel.com>"); 119