[PATCH v1 08/12] input: keypad-matrix: tell GPIO pins from matrix lines
Stephen Warren
swarren at wwwdotorg.org
Sat Jun 29 00:35:42 EST 2013
On 06/28/2013 01:52 AM, Gerhard Sittig wrote:
>
> [ late reply, just catching up with the backlog ]
>
> On Mon, Jun 24, 2013 at 17:26 -0600, Stephen Warren wrote:
>>
>> [ ... sparse matrices, not all columns/rows populated ... ]
>> On some Tegra boards, there end up
>> being rather tri-angular keymaps, where key positions (0, 0), (0, 1),
>> (0, 2), (1, 1), (1, 2), (2, 2) end up being used. In this scenario,
>> detailed investigation of the keymap would reveal:
>>
>> * Only scan columns 0..2
>> * For column 0, scan rows 0..2
>> * For column 1, scan rows 1..2
>> * For columm 2, scan row 2.
>
> That's another question I had. So far I was concerned with just
> polling or scanning the relevant columns, while all the rows for
> a given column were queried (as the driver always used to do).
>
> Now you raise the question of whether rows should get queried as
> well depending on whether "a key may sit there". It wasn't the
> exact question I raised, but I added a comment to the spot where
> input subsystem events get generated: Is the driver expected to
> emit events for matrix positions where no key map entry exists?
I would assume there is no need to, but I don't know for sure. Perhaps
Dmitry can answer that?
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