Hi,
On 02-07-16 13:02, Maxime Ripard wrote:
On Sat, Jul 02, 2016 at 11:32:07AM +0200, Hans de Goede wrote:
Hi,
On 02-07-16 11:12, Chen-Yu Tsai wrote:
Hi,
On Sat, Jul 2, 2016 at 5:00 AM, Alexandre Belloni
<alexandre.belloni@xxxxxxxxxxxxxxxxxx> wrote:
Document the bindings for the Allwinner LRADC.
We already have Documentation/devicetree/bindings/input/sun4i-lradc-keys.txt
and I'm pretty sure Hans (CC-ed) argued that this is not a generic ADC
block.
Right, this block is used on many tablets and some dev boards to
provide buttons (as in the hid type) and the block is designed for
this purpose, giving an irq when the adc level crosses a certain
threshold.
Sure it can be used in a more generic way, but that is not its
primary goal.
We've always had a different view on this, but it's a detail :)
So any generic purpose adc driver must not break the current
use-case (which is already used in mainline kernel dts files
in plenty of cases).
Yep.
I believe that the best way to deal with this is to add an
"allwinner,general-purpose-mode" flag to the existing binding
(as well as document general purpose mode in the existing
binding rather then in a new binding doc).
That seems to be the right thing to do purely looking at this
from a dt binding pov.
There's a way simpler solution: if there's no child nodes, it's meant
to be used as an ADC, otherwise, as input.
The logic will have to be a bit more complex than that, since there's
two channels, and you could only require one for the buttons, leaving
the other one available as an ADC.
But that doesn't require any new property.
True, if there are no button nodes, then go general-purpose will
work too.
For the implementation of this we can simpy have 2 drivers,
then both drivers can check the flag and if present return
-ENODEV from the existing input driver and likewise if not
present return -ENODEV from the iio driver.
We may actually use a similar solution for the touchscreen
controller which can also be alternatively used as a generic
purpose adc.
There's no need to keep both drivers as long as we keep the features
and bindings.
That is also true.
Regards,
Hans
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