0001 =================
0002 Triggered Buffers
0003 =================
0004
0005 Now that we know what buffers and triggers are let's see how they work together.
0006
0007 IIO triggered buffer setup
0008 ==========================
0009
0010 * :c:func:`iio_triggered_buffer_setup` — Setup triggered buffer and pollfunc
0011 * :c:func:`iio_triggered_buffer_cleanup` — Free resources allocated by
0012 :c:func:`iio_triggered_buffer_setup`
0013 * struct iio_buffer_setup_ops — buffer setup related callbacks
0014
0015 A typical triggered buffer setup looks like this::
0016
0017 const struct iio_buffer_setup_ops sensor_buffer_setup_ops = {
0018 .preenable = sensor_buffer_preenable,
0019 .postenable = sensor_buffer_postenable,
0020 .postdisable = sensor_buffer_postdisable,
0021 .predisable = sensor_buffer_predisable,
0022 };
0023
0024 irqreturn_t sensor_iio_pollfunc(int irq, void *p)
0025 {
0026 pf->timestamp = iio_get_time_ns((struct indio_dev *)p);
0027 return IRQ_WAKE_THREAD;
0028 }
0029
0030 irqreturn_t sensor_trigger_handler(int irq, void *p)
0031 {
0032 u16 buf[8];
0033 int i = 0;
0034
0035 /* read data for each active channel */
0036 for_each_set_bit(bit, active_scan_mask, masklength)
0037 buf[i++] = sensor_get_data(bit)
0038
0039 iio_push_to_buffers_with_timestamp(indio_dev, buf, timestamp);
0040
0041 iio_trigger_notify_done(trigger);
0042 return IRQ_HANDLED;
0043 }
0044
0045 /* setup triggered buffer, usually in probe function */
0046 iio_triggered_buffer_setup(indio_dev, sensor_iio_polfunc,
0047 sensor_trigger_handler,
0048 sensor_buffer_setup_ops);
0049
0050 The important things to notice here are:
0051
0052 * :c:type:`iio_buffer_setup_ops`, the buffer setup functions to be called at
0053 predefined points in the buffer configuration sequence (e.g. before enable,
0054 after disable). If not specified, the IIO core uses the default
0055 iio_triggered_buffer_setup_ops.
0056 * **sensor_iio_pollfunc**, the function that will be used as top half of poll
0057 function. It should do as little processing as possible, because it runs in
0058 interrupt context. The most common operation is recording of the current
0059 timestamp and for this reason one can use the IIO core defined
0060 :c:func:`iio_pollfunc_store_time` function.
0061 * **sensor_trigger_handler**, the function that will be used as bottom half of
0062 the poll function. This runs in the context of a kernel thread and all the
0063 processing takes place here. It usually reads data from the device and
0064 stores it in the internal buffer together with the timestamp recorded in the
0065 top half.
0066
0067 More details
0068 ============
0069 .. kernel-doc:: drivers/iio/buffer/industrialio-triggered-buffer.c
