mirror of
https://github.com/edk2-porting/linux-next.git
synced 2024-12-28 15:13:55 +08:00
49b2fd6ea6
This is a manual conversion of the existing DocBook documentation for IIO. The intent is not to substantially change any of the content in this patch, but to give a base to build upon. Signed-off-by: Jonathan Cameron <jic23@kernel.org> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
70 lines
2.6 KiB
ReStructuredText
70 lines
2.6 KiB
ReStructuredText
=================
|
|
Triggered Buffers
|
|
=================
|
|
|
|
Now that we know what buffers and triggers are let's see how they work together.
|
|
|
|
IIO triggered buffer setup
|
|
==========================
|
|
|
|
* :c:func:`iio_triggered_buffer_setup` — Setup triggered buffer and pollfunc
|
|
* :c:func:`iio_triggered_buffer_cleanup` — Free resources allocated by
|
|
:c:func:`iio_triggered_buffer_setup`
|
|
* struct :c:type:`iio_buffer_setup_ops` — buffer setup related callbacks
|
|
|
|
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((struct indio_dev *)p);
|
|
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:
|
|
|
|
* :c:type:`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
|
|
:c:func:`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.
|
|
|
|
More details
|
|
============
|
|
.. kernel-doc:: drivers/iio/buffer/industrialio-triggered-buffer.c
|