drivers/iio/dummy/iio_simple_dummy_buffer.c

Source file repositories/reference/linux-study-clean/drivers/iio/dummy/iio_simple_dummy_buffer.c

File Facts

System
Linux kernel
Corpus path
drivers/iio/dummy/iio_simple_dummy_buffer.c
Extension
.c
Size
3348 bytes
Lines
118
Domain
Driver Families
Bucket
drivers/iio
Inferred role
Driver Families: implementation source
Status
source implementation candidate

Why This File Exists

Repeatable hardware-adapter layer. Deep compatibility for every driver is out of scope; this atlas records patterns, probe lifecycles, bus glue, IRQ/DMA usage, and links back to core abstractions.

Dependency Surface

Detected Declarations

Annotated Snippet

struct dummy_scan {
	s16 data[ARRAY_SIZE(fakedata)];
	aligned_s64 timestamp;
};

/**
 * iio_simple_dummy_trigger_h() - the trigger handler function
 * @irq: the interrupt number
 * @p: private data - always a pointer to the poll func.
 *
 * This is the guts of buffered capture. On a trigger event occurring,
 * if the pollfunc is attached then this handler is called as a threaded
 * interrupt (and hence may sleep). It is responsible for grabbing data
 * from the device and pushing it into the associated buffer.
 */
static irqreturn_t iio_simple_dummy_trigger_h(int irq, void *p)
{
	struct iio_poll_func *pf = p;
	struct iio_dev *indio_dev = pf->indio_dev;
	struct dummy_scan *scan;
	int i = 0, j;

	/*
	 * Note that some buses such as SPI require DMA safe buffers which
	 * cannot be on the stack. Two easy ways to do this:
	 *  - Local kzalloc (as done here)
	 *  - A buffer at the end of the structure accessed via iio_priv()
	 *    that is marked __aligned(IIO_DMA_MINALIGN).
	 */
	scan = kzalloc_obj(*scan);
	if (!scan)
		goto done;

	/*
	 * Three common options here:
	 * hardware scans:
	 *   certain combinations of channels make up a fast read. The capture
	 *   will consist of all of them. Hence we just call the grab data
	 *   function and fill the buffer without processing.
	 * software scans:
	 *   can be considered to be random access so efficient reading is just
	 *   a case of minimal bus transactions.
	 * software culled hardware scans:
	 *   occasionally a driver may process the nearest hardware scan to avoid
	 *   storing elements that are not desired. This is the fiddliest option
	 *   by far.
	 * Here let's pretend we have random access. And the values are in the
	 * constant table fakedata.
	 */
	iio_for_each_active_channel(indio_dev, j)
		scan->data[i++] = fakedata[j];

	iio_push_to_buffers_with_ts(indio_dev, scan, sizeof(*scan),
				    iio_get_time_ns(indio_dev));

	kfree(scan);
done:
	/*
	 * Tell the core we are done with this trigger and ready for the
	 * next one.
	 */
	iio_trigger_notify_done(indio_dev->trig);

	return IRQ_HANDLED;
}

static const struct iio_buffer_setup_ops iio_simple_dummy_buffer_setup_ops = {
};

int iio_simple_dummy_configure_buffer(struct iio_dev *indio_dev)
{
	return iio_triggered_buffer_setup(indio_dev, NULL,
					  iio_simple_dummy_trigger_h,
					  &iio_simple_dummy_buffer_setup_ops);
}

/**
 * iio_simple_dummy_unconfigure_buffer() - release buffer resources
 * @indio_dev: device instance state
 */
void iio_simple_dummy_unconfigure_buffer(struct iio_dev *indio_dev)
{
	iio_triggered_buffer_cleanup(indio_dev);
}

Annotation

Implementation Notes