Re: [PATCH 1/1] TWL4030 keypad: keypad lock / unlock

[Mark Brown <broonie@opensource.wolfsonmicro.com>]

On Wed, Nov 11, 2009 at 11:57:36AM +0200, Onkalo Samu wrote:
> On Tue, 2009-11-10 at 18:26 +0100, ext Dmitry Torokhov wrote:

> > It seems that Samu's patch is a bit different - it completely disables
> > the keypad. But I wonder if it needs the special attribute or the same
> > can be simply achieved by simply closing event device when it is not
> > needed. Or maybe unbinding driver through sysfs.

> Yes, purpose is to provide keylock feature which totally disables the
> keymatrix. This way system is not even aware that some key was pressed.
> It also helps to save power since unnecessary interrupts are not
> received.

OK, that's not what your patch description sounded like - it was talking
specifically about preventing resume so I thought it was focused on
suspend and resume.

> It seems that several userspace programs are reading the device. I have
> no idea how to get all the users to close the device when keylock is
> needed. Could be quite big number of changes to here and there in
> userspace side.

This sounds like something that should have a generic API for - keylock
functionality is a very common feature.

> > Overall it seems that every input device used in embedded has it's own
> > way of disabling itself, we need a generic solution... Maybe
> > userspace-controlled PM is the answer).

> That is something which should be somehow handled. Depending on what is
> happening at the userspace, there can be different needs for input
> devices. Current way will be a mess since every driver has its own
> tricks to save power. But power saving is really needed for embedded
> devices.

It doesn't look that bad to me, to be honest - mostly it seems to be a
case of shutting down the device as much as possible when it's closed
plus other things that the particular device can get away with without
impacting actual operation.