drivers/iio/trigger/iio-trig-loop.c

   1 /*
   2  * Copyright 2016 Jonathan Cameron <jic23@kernel.org>
   3  *
   4  * Licensed under the GPL-2.
   5  *
   6  * Based on a mashup of the hrtimer trigger and continuous sampling proposal of
   7  * Gregor Boirie <gregor.boirie@parrot.com>
   8  *
   9  * Note this is still rather experimental and may eat babies.
  10  *
  11  * Todo
  12  * * Protect against connection of devices that 'need' the top half
  13  *   handler.
  14  * * Work out how to run top half handlers in this context if it is
  15  *   safe to do so (timestamp grabbing for example)
  16  *
  17  * Tested against a max1363. Used about 33% cpu for the thread and 20%
  18  * for generic_buffer piping to /dev/null. Watermark set at 64 on a 128
  19  * element kfifo buffer.
  20  */
  21
  22 #include <linux/kernel.h>
  23 #include <linux/module.h>
  24 #include <linux/platform_device.h>
  25 #include <linux/slab.h>
  26 #include <linux/irq_work.h>
  27 #include <linux/kthread.h>
  28 #include <linux/freezer.h>
  29
  30 #include <linux/iio/iio.h>
  31 #include <linux/iio/trigger.h>
  32 #include <linux/iio/sw_trigger.h>
  33
  34 struct iio_loop_info {
  35         struct iio_sw_trigger swt;
  36         struct task_struct *task;
  37 };
  38
  39 static struct config_item_type iio_loop_type = {
  40         .ct_owner = THIS_MODULE,
  41 };
  42
  43 static int iio_loop_thread(void *data)
  44 {
  45         struct iio_trigger *trig = data;
  46
  47         set_freezable();
  48
  49         do {
  50                 iio_trigger_poll_chained(trig);
  51         } while (likely(!kthread_freezable_should_stop(NULL)));
  52
  53         return 0;
  54 }
  55
  56 static int iio_loop_trigger_set_state(struct iio_trigger *trig, bool state)
  57 {
  58         struct iio_loop_info *loop_trig = iio_trigger_get_drvdata(trig);
  59
  60         if (state) {
  61                 loop_trig->task = kthread_run(iio_loop_thread,
  62                                               trig, trig->name);
  63                 if (unlikely(IS_ERR(loop_trig->task))) {
  64                         dev_err(&trig->dev,
  65                                 "failed to create trigger loop thread\n");
  66                         return PTR_ERR(loop_trig->task);
  67                 }
  68         } else {
  69                 kthread_stop(loop_trig->task);
  70         }
  71
  72         return 0;
  73 }
  74
  75 static const struct iio_trigger_ops iio_loop_trigger_ops = {
  76         .set_trigger_state = iio_loop_trigger_set_state,
  77 };
  78
  79 static struct iio_sw_trigger *iio_trig_loop_probe(const char *name)
  80 {
  81         struct iio_loop_info *trig_info;
  82         int ret;
  83
  84         trig_info = kzalloc(sizeof(*trig_info), GFP_KERNEL);
  85         if (!trig_info)
  86                 return ERR_PTR(-ENOMEM);
  87
  88         trig_info->swt.trigger = iio_trigger_alloc("%s", name);
  89         if (!trig_info->swt.trigger) {
  90                 ret = -ENOMEM;
  91                 goto err_free_trig_info;
  92         }
  93
  94         iio_trigger_set_drvdata(trig_info->swt.trigger, trig_info);
  95         trig_info->swt.trigger->ops = &iio_loop_trigger_ops;
  96
  97         ret = iio_trigger_register(trig_info->swt.trigger);
  98         if (ret)
  99                 goto err_free_trigger;
 100
 101         iio_swt_group_init_type_name(&trig_info->swt, name, &iio_loop_type);
 102
 103         return &trig_info->swt;
 104
 105 err_free_trigger:
 106         iio_trigger_free(trig_info->swt.trigger);
 107 err_free_trig_info:
 108         kfree(trig_info);
 109
 110         return ERR_PTR(ret);
 111 }
 112
 113 static int iio_trig_loop_remove(struct iio_sw_trigger *swt)
 114 {
 115         struct iio_loop_info *trig_info;
 116
 117         trig_info = iio_trigger_get_drvdata(swt->trigger);
 118
 119         iio_trigger_unregister(swt->trigger);
 120         iio_trigger_free(swt->trigger);
 121         kfree(trig_info);
 122
 123         return 0;
 124 }
 125
 126 static const struct iio_sw_trigger_ops iio_trig_loop_ops = {
 127         .probe = iio_trig_loop_probe,
 128         .remove = iio_trig_loop_remove,
 129 };
 130
 131 static struct iio_sw_trigger_type iio_trig_loop = {
 132         .name = "loop",
 133         .owner = THIS_MODULE,
 134         .ops = &iio_trig_loop_ops,
 135 };
 136
 137 module_iio_sw_trigger_driver(iio_trig_loop);
 138
 139 MODULE_AUTHOR("Jonathan Cameron <jic23@kernel.org>");
 140 MODULE_DESCRIPTION("Loop based trigger for the iio subsystem");
 141 MODULE_LICENSE("GPL v2");
 142 MODULE_ALIAS("platform:iio-trig-loop");