Re: [PATCH 2/2] Input: add touchscreen support for TS-4800

[Damien Riegel <damien.riegel@savoirfairelinux.com>]

Hi Dmitry

On Sat, Dec 12, 2015 at 08:58:58PM -0800, Dmitry Torokhov wrote:
> Hi Damien,
> 
> On Thu, Dec 10, 2015 at 11:11:12AM -0500, Damien Riegel wrote:
> > On this board, the touchscreen, an ads7843, is not handled directly by
> > Linux but by a companion FPGA. This FPGA is memory-mapped and the IP
> > design is very similar to the mk712.
> 
> ...
> 
> > +
> > +	poll_dev = devm_input_allocate_polled_device(&pdev->dev);
> > +	if (!poll_dev)
> > +		return -ENOMEM;
> 
> I wonder how useful touchscreen implemented as polling device is. Isn't
> there an interrupt line for it?
 
There is an interrupt line between the touchscreen and the FGPA, but not
between the FPGA and the SoC. I agree it is a bit peculiar. Hopefully on
more recent boards, they changed their design to handle the touchscreen
directly with Linux.

Thanks,
Damien

> Thanks.
> 
> -- 
> Dmitry