70 lines
2.6 KiB
ReStructuredText
70 lines
2.6 KiB
ReStructuredText
=================
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Triggered Buffers
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=================
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Now that we know what buffers and triggers are let's see how they work together.
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IIO triggered buffer setup
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==========================
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* :c:func:`iio_triggered_buffer_setup` — Setup triggered buffer and pollfunc
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* :c:func:`iio_triggered_buffer_cleanup` — Free resources allocated by
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:c:func:`iio_triggered_buffer_setup`
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* struct iio_buffer_setup_ops — buffer setup related callbacks
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A typical triggered buffer setup looks like this::
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const struct iio_buffer_setup_ops sensor_buffer_setup_ops = {
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.preenable = sensor_buffer_preenable,
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.postenable = sensor_buffer_postenable,
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.postdisable = sensor_buffer_postdisable,
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.predisable = sensor_buffer_predisable,
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};
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irqreturn_t sensor_iio_pollfunc(int irq, void *p)
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{
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pf->timestamp = iio_get_time_ns((struct indio_dev *)p);
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return IRQ_WAKE_THREAD;
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}
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irqreturn_t sensor_trigger_handler(int irq, void *p)
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{
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u16 buf[8];
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int i = 0;
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/* read data for each active channel */
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for_each_set_bit(bit, active_scan_mask, masklength)
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buf[i++] = sensor_get_data(bit)
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iio_push_to_buffers_with_timestamp(indio_dev, buf, timestamp);
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iio_trigger_notify_done(trigger);
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return IRQ_HANDLED;
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}
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/* setup triggered buffer, usually in probe function */
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iio_triggered_buffer_setup(indio_dev, sensor_iio_polfunc,
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sensor_trigger_handler,
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sensor_buffer_setup_ops);
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The important things to notice here are:
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* :c:type:`iio_buffer_setup_ops`, the buffer setup functions to be called at
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predefined points in the buffer configuration sequence (e.g. before enable,
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after disable). If not specified, the IIO core uses the default
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iio_triggered_buffer_setup_ops.
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* **sensor_iio_pollfunc**, the function that will be used as top half of poll
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function. It should do as little processing as possible, because it runs in
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interrupt context. The most common operation is recording of the current
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timestamp and for this reason one can use the IIO core defined
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:c:func:`iio_pollfunc_store_time` function.
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* **sensor_trigger_handler**, the function that will be used as bottom half of
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the poll function. This runs in the context of a kernel thread and all the
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processing takes place here. It usually reads data from the device and
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stores it in the internal buffer together with the timestamp recorded in the
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top half.
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More details
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============
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.. kernel-doc:: drivers/iio/buffer/industrialio-triggered-buffer.c
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