Re: Behaviour of input-polldev?

[Dmitry Torokhov <dmitry.torokhov@gmail.com>]

On Tue, Sep 03, 2013 at 01:54:45PM +0200, David Herrmann wrote:
> Hi Florian
> 
> On Tue, Sep 3, 2013 at 1:39 PM, Florian Echtler <floe@butterbrot.org> wrote:
> > Hello everyone,
> >
> > I'm in the process of writing an input driver for the Microsoft
> > Pixelsense (formerly Surface 2.0). The device only has bulk endpoints
> > and consequently needs to be polled regularly. My beta driver uses
> > input-polldev for this, and it appears to work nicely, however, I
> > couldn't find out how input-polldev behaves if one polling cycle takes
> > longer than expected and a new poll would already be triggered while the
> > first one is still running?

With input-polldev new poll can not get scheduled until driver's poll()
method returns:

static void input_polled_device_work(struct work_struct *work)
{
	struct input_polled_dev *dev =
		container_of(work, struct input_polled_dev, work.work);

	dev->poll(dev);
	input_polldev_queue_work(dev);
}

The expectation here is that poll function is quick and does not
introduce much skew into scheduling of polls (although of course error
is accumulating).

-- 
Dmitry