Re: [PATCH] Input: matrix-keypad - support binary column select gpios

[Anatolij Gustschin <agust@denx.de>]

Hi Dmitry,

On Tue, 29 Jan 2013 17:16:29 -0800
Dmitry Torokhov <dmitry.torokhov@gmail.com> wrote:
...
> On Tue, Jan 29, 2013 at 01:25:24PM +0100, Anatolij Gustschin wrote:
> > On hardware with limited gpios one column select gpio can select
> > two different rows when using some additional hardware logic:
> > high value selects one row, low value selects another row. Add
> > support for such matrix keyboards and document device tree
> > bindings used to describe them.
> > 
> > Since half of the columns is always not selected, interrupts won't be
> > generated for press events on these columns. To generate interrupts
> > for not selected columns we need to periodicaly switch to these columns
> > in order to catch the potential press events. This is done by additional
> > work function.
> 
> So this effectively switches the driver from interrupt driven to polled
> model, right? The device does not really need an interrupt anymore...

Yes, partially. I do not need to scan the state of the rows right
after column switching. The interrupts for press events will only be
generated if a key in the affected row was actually pressed. So the
device is still interrupt driven and the row state read-out happens
in the work scheduled from the interrupt handler.

Thanks,

Anatolij