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

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright 2016 Jonathan Cameron <jic23@kernel.org>
   4  *
   5  * Based on a mashup of the hrtimer trigger and continuous sampling proposal of
   6  * Gregor Boirie <gregor.boirie@parrot.com>
   7  *
   8  * Note this is still rather experimental and may eat babies.
   9  *
  10  * Todo
  11  * * Protect against connection of devices that 'need' the top half
  12  *   handler.
  13  * * Work out how to run top half handlers in this context if it is
  14  *   safe to do so (timestamp grabbing for example)
  15  *
  16  * Tested against a max1363. Used about 33% cpu for the thread and 20%
  17  * for generic_buffer piping to /dev/null. Watermark set at 64 on a 128
  18  * element kfifo buffer.
  19  */
  20
  21 #include <linux/kernel.h>
  22 #include <linux/module.h>
  23 #include <linux/platform_device.h>
  24 #include <linux/slab.h>
  25 #include <linux/irq_work.h>
  26 #include <linux/kthread.h>
  27 #include <linux/freezer.h>
  28
  29 #include <linux/iio/iio.h>
  30 #include <linux/iio/trigger.h>
  31 #include <linux/iio/sw_trigger.h>
  32
  33 struct iio_loop_info {
  34         struct iio_sw_trigger swt;
  35         struct task_struct *task;
  36 };
  37
  38 static const struct config_item_type iio_loop_type = {
  39         .ct_owner = THIS_MODULE,
  40 };
  41
  42 static int iio_loop_thread(void *data)
  43 {
  44         struct iio_trigger *trig = data;
  45
  46         set_freezable();
  47
  48         do {
  49                 iio_trigger_poll_chained(trig);
  50         } while (likely(!kthread_freezable_should_stop(NULL)));
  51
  52         return 0;
  53 }
  54
  55 static int iio_loop_trigger_set_state(struct iio_trigger *trig, bool state)
  56 {
  57         struct iio_loop_info *loop_trig = iio_trigger_get_drvdata(trig);
  58
  59         if (state) {
  60                 loop_trig->task = kthread_run(iio_loop_thread,
  61                                               trig, trig->name);
  62                 if (IS_ERR(loop_trig->task)) {
  63                         dev_err(&trig->dev,
  64                                 "failed to create trigger loop thread\n");
  65                         return PTR_ERR(loop_trig->task);
  66                 }
  67         } else {
  68                 kthread_stop(loop_trig->task);
  69         }
  70
  71         return 0;
  72 }
  73
  74 static const struct iio_trigger_ops iio_loop_trigger_ops = {
  75         .set_trigger_state = iio_loop_trigger_set_state,
  76 };
  77
  78 static struct iio_sw_trigger *iio_trig_loop_probe(const char *name)
  79 {
  80         struct iio_loop_info *trig_info;
  81         int ret;
  82
  83         trig_info = kzalloc(sizeof(*trig_info), GFP_KERNEL);
  84         if (!trig_info)
  85                 return ERR_PTR(-ENOMEM);
  86
  87         trig_info->swt.trigger = iio_trigger_alloc("%s", name);
  88         if (!trig_info->swt.trigger) {
  89                 ret = -ENOMEM;
  90                 goto err_free_trig_info;
  91         }
  92
  93         iio_trigger_set_drvdata(trig_info->swt.trigger, trig_info);
  94         trig_info->swt.trigger->ops = &iio_loop_trigger_ops;
  95
  96         ret = iio_trigger_register(trig_info->swt.trigger);
  97         if (ret)
  98                 goto err_free_trigger;
  99
 100         iio_swt_group_init_type_name(&trig_info->swt, name, &iio_loop_type);
 101
 102         return &trig_info->swt;
 103
 104 err_free_trigger:
 105         iio_trigger_free(trig_info->swt.trigger);
 106 err_free_trig_info:
 107         kfree(trig_info);
 108
 109         return ERR_PTR(ret);
 110 }
 111
 112 static int iio_trig_loop_remove(struct iio_sw_trigger *swt)
 113 {
 114         struct iio_loop_info *trig_info;
 115
 116         trig_info = iio_trigger_get_drvdata(swt->trigger);
 117
 118         iio_trigger_unregister(swt->trigger);
 119         iio_trigger_free(swt->trigger);
 120         kfree(trig_info);
 121
 122         return 0;
 123 }
 124
 125 static const struct iio_sw_trigger_ops iio_trig_loop_ops = {
 126         .probe = iio_trig_loop_probe,
 127         .remove = iio_trig_loop_remove,
 128 };
 129
 130 static struct iio_sw_trigger_type iio_trig_loop = {
 131         .name = "loop",
 132         .owner = THIS_MODULE,
 133         .ops = &iio_trig_loop_ops,
 134 };
 135
 136 module_iio_sw_trigger_driver(iio_trig_loop);
 137
 138 MODULE_AUTHOR("Jonathan Cameron <jic23@kernel.org>");
 139 MODULE_DESCRIPTION("Loop based trigger for the iio subsystem");
 140 MODULE_LICENSE("GPL v2");
 141 MODULE_ALIAS("platform:iio-trig-loop");