linux-kernel - Re: [v2,2/4] Input: mt-matrix-keypad: Add Bosch mt matrix keypad driver

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Date:   Fri, 19 Aug 2022 06:56:33 +0000
From:   <Gireesh.Hiremath@...bosch.com>
To:     <krzysztof.kozlowski+dt@...aro.org>
CC:     <m.felsch@...gutronix.de>, <linux-omap@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-input@...r.kernel.org>, <bcousson@...libre.com>,
        <tony@...mide.com>, <robh+dt@...nel.org>,
        <dmitry.torokhov@...il.com>, <mkorpershoek@...libre.com>,
        <davidgow@...gle.com>, <swboyd@...omium.org>,
        <fengping.yu@...iatek.com>, <y.oudjana@...tonmail.com>,
        <rdunlap@...radead.org>, <colin.king@...el.com>,
        <Gireesh.Hiremath@...bosch.com>, <sjoerd.simons@...labora.co.uk>,
        <VinayKumar.Shettar@...bosch.com>,
        <Govindaraji.Sivanantham@...bosch.com>,
        <anaclaudia.dias@...bosch.com>
Subject: Re: [v2,2/4] Input: mt-matrix-keypad: Add Bosch mt matrix keypad driver

From: Gireesh Hiremath <Gireesh.Hiremath@...bosch.com>

Hi Krzysztof,

>>> You wrote pretty long message explaining how the device works, but I
>>> still do not see the answer to questions - why it cannot be part of
>>> matrix keypad?
>> 
>> Following are the difference between matrix keypad and Bosch keypad
>> make us to add another keypad driver.
>> 
>> matrix keypad:
>> 	- By hardware schematic, a column GPIO line will intersect only
>> 	  with row GPIO lines, not with the other column GPIO lines
>> 	- so, row and column GPIO property are fixed, because of this
>> 	- key scanning work based on interrupt mode
>> 	- and key press is determined based on setting column as output,
>> 	  row GPIO as input and set interrupt to monitor the changes in state,
>> 	  serve the key pressed in ISR
>> 
>> Bosch keypad:
>>     - By hardware schematic column GPIO line can intersect with row GPIO line
>> 	  as well as other column GPIO lines
>> 	- so, all GPIO act as row as well as column, because of this
>> 	- key scanning based on polling mode
>> 	- a key pressed is determined by setting one of GPIO line as output and
>> 	  other as input and poll for change in the state of input GPIO lines.
>> 	  Setting one of a GPIO line as output and remaining GPIO lines as input is on
>> 	  round robin bases.
>
>Which is still not the answer "why it cannot be part of matrix keypad?".
>To me looks similar enough, although maybe not exactly superset of the
>other.

I have merged the Bosch keypad in to the matrix keypad
and sending version v3 patches to support that.

v3-0001-driver-input-matric-keypad-switch-to-gpiod.patch
v3-0002-driver-input-matric-keypad-add-reduced-matrix-sup.patch
v3-0003-dt-bindings-input-gpio-matrix-keypad-add-reduced-.patch 

>
>>>
>>> "It looks like this driver has smaller number of features than
>>> matrix-keypad, so it should be integrated into the matrix-keypad.
>>> matrix-keypad features are superset to this one."
>>>
>>> "But anyway this should be just merged into matrix-keypad. It's a
>>> simpler set of that binding."
>> 
>> This keypad driver specific to Bosch measuring tool or similar devices.
>> Please let me know to send latest patch which resolves build warning
>> and gpiod API support.
>
>That's a poor reason not to merge into existing driver... I am sorry,
>but our entire Linux kernel concept is to integrate, not duplicate. If
>each of vendors wanted their own feature, we would have unmanageable
>monstrosity with millions of drivers doing almost the same...
>
>
>Best regards,
>Krzysztof
>

Best regards,
Gireesh Hiremath