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