1 files changed, 141 insertions, 0 deletions
diff --git a/drivers/iio/trigger/iio-trig-loop.c b/drivers/iio/trigger/iio-trig-loop.c
new file mode 100644
index 000000000..96ec06bbe
--- /dev/null
+++ b/drivers/iio/trigger/iio-trig-loop.c
@@ -0,0 +1,141 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright 2016 Jonathan Cameron <jic23@kernel.org>
+ *
+ * Based on a mashup of the hrtimer trigger and continuous sampling proposal of
+ * Gregor Boirie <gregor.boirie@parrot.com>
+ *
+ * Note this is still rather experimental and may eat babies.
+ *
+ * Todo
+ * * Protect against connection of devices that 'need' the top half
+ *   handler.
+ * * Work out how to run top half handlers in this context if it is
+ *   safe to do so (timestamp grabbing for example)
+ *
+ * Tested against a max1363. Used about 33% cpu for the thread and 20%
+ * for generic_buffer piping to /dev/null. Watermark set at 64 on a 128
+ * element kfifo buffer.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+#include <linux/irq_work.h>
+#include <linux/kthread.h>
+#include <linux/freezer.h>
+
+#include <linux/iio/iio.h>
+#include <linux/iio/trigger.h>
+#include <linux/iio/sw_trigger.h>
+
+struct iio_loop_info {
+	struct iio_sw_trigger swt;
+	struct task_struct *task;
+};
+
+static const struct config_item_type iio_loop_type = {
+	.ct_owner = THIS_MODULE,
+};
+
+static int iio_loop_thread(void *data)
+{
+	struct iio_trigger *trig = data;
+
+	set_freezable();
+
+	do {
+		iio_trigger_poll_chained(trig);
+	} while (likely(!kthread_freezable_should_stop(NULL)));
+
+	return 0;
+}
+
+static int iio_loop_trigger_set_state(struct iio_trigger *trig, bool state)
+{
+	struct iio_loop_info *loop_trig = iio_trigger_get_drvdata(trig);
+
+	if (state) {
+		loop_trig->task = kthread_run(iio_loop_thread,
+					      trig, trig->name);
+		if (IS_ERR(loop_trig->task)) {
+			dev_err(&trig->dev,
+				"failed to create trigger loop thread\n");
+			return PTR_ERR(loop_trig->task);
+		}
+	} else {
+		kthread_stop(loop_trig->task);
+	}
+
+	return 0;
+}
+
+static const struct iio_trigger_ops iio_loop_trigger_ops = {
+	.set_trigger_state = iio_loop_trigger_set_state,
+};
+
+static struct iio_sw_trigger *iio_trig_loop_probe(const char *name)
+{
+	struct iio_loop_info *trig_info;
+	int ret;
+
+	trig_info = kzalloc(sizeof(*trig_info), GFP_KERNEL);
+	if (!trig_info)
+		return ERR_PTR(-ENOMEM);
+
+	trig_info->swt.trigger = iio_trigger_alloc(NULL, "%s", name);
+	if (!trig_info->swt.trigger) {
+		ret = -ENOMEM;
+		goto err_free_trig_info;
+	}
+
+	iio_trigger_set_drvdata(trig_info->swt.trigger, trig_info);
+	trig_info->swt.trigger->ops = &iio_loop_trigger_ops;
+
+	ret = iio_trigger_register(trig_info->swt.trigger);
+	if (ret)
+		goto err_free_trigger;
+
+	iio_swt_group_init_type_name(&trig_info->swt, name, &iio_loop_type);
+
+	return &trig_info->swt;
+
+err_free_trigger:
+	iio_trigger_free(trig_info->swt.trigger);
+err_free_trig_info:
+	kfree(trig_info);
+
+	return ERR_PTR(ret);
+}
+
+static int iio_trig_loop_remove(struct iio_sw_trigger *swt)
+{
+	struct iio_loop_info *trig_info;
+
+	trig_info = iio_trigger_get_drvdata(swt->trigger);
+
+	iio_trigger_unregister(swt->trigger);
+	iio_trigger_free(swt->trigger);
+	kfree(trig_info);
+
+	return 0;
+}
+
+static const struct iio_sw_trigger_ops iio_trig_loop_ops = {
+	.probe = iio_trig_loop_probe,
+	.remove = iio_trig_loop_remove,
+};
+
+static struct iio_sw_trigger_type iio_trig_loop = {
+	.name = "loop",
+	.owner = THIS_MODULE,
+	.ops = &iio_trig_loop_ops,
+};
+
+module_iio_sw_trigger_driver(iio_trig_loop);
+
+MODULE_AUTHOR("Jonathan Cameron <jic23@kernel.org>");
+MODULE_DESCRIPTION("Loop based trigger for the iio subsystem");
+MODULE_LICENSE("GPL v2");
+MODULE_ALIAS("platform:iio-trig-loop");