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Message-ID: <665c9aa5-ef70-65ce-7d9c-4b3b93874934@linaro.org>
Date:   Tue, 6 Jun 2023 20:55:35 +0200
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From:   Neil Armstrong <neil.armstrong@linaro.org>
Reply-To: neil.armstrong@linaro.org
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To:     Dmitry Torokhov <dmitry.torokhov@gmail.com>
Cc:     Hans de Goede <hdegoede@redhat.com>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Conor Dooley <conor+dt@kernel.org>,
        Bastien Nocera <hadess@hadess.net>,
        Henrik Rydberg <rydberg@bitmath.org>,
        linux-input@vger.kernel.org, linux-arm-msm@vger.kernel.org,
        devicetree@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20230606-topic-goodix-berlin-upstream-initial-v1-0-4a0741b8aefd@linaro.org>
 <f5f20de8-851a-fe20-4664-62b6de14ebd7@redhat.com>
 <2677ae8c-59d3-b658-dc3f-918838ac0fb6@linaro.org>
 <ZH9+ndrF0RIgFhnI@google.com>
Organization: Linaro Developer Services
Subject: Re: [PATCH RFC 0/4] input: touchscreen: add initial support for
 Goodix Berlin touchscreen IC
In-Reply-To: <ZH9+ndrF0RIgFhnI@google.com>
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Hi Dmitry,

On 06/06/2023 20:44, Dmitry Torokhov wrote:
> On Tue, Jun 06, 2023 at 08:12:04PM +0200, Neil Armstrong wrote:
>> Hi,
>>
>> On 06/06/2023 17:31, Hans de Goede wrote:
>>> Hi Neil,
>>>
>>> On 6/6/23 16:31, Neil Armstrong wrote:
>>>> These touchscreen ICs support SPI, I2C and I3C interface, up to
>>>> 10 finger touch, stylus and gestures events.
>>>>
>>>> This initial driver is derived from the Goodix goodix_ts_berlin
>>>> available at [1] and [2] and only supports the GT9916 IC
>>>> present on the Qualcomm SM8550 MTP & QRD touch panel.
>>>>
>>>> The current implementation only supports BerlinD, aka GT9916.
>>>>
>>>> Support for advanced features like:
>>>> - Firmware & config update
>>>> - Stylus events
>>>> - Gestures events
>>>> - Previous revisions support (BerlinA or BerlinB)
>>>> is not included in current version.
>>>>
>>>> The current support will work with currently flashed firmware
>>>> and config, and bail out if firmware or config aren't flashed yet.
>>>
>>> What I'm missing here / in the commit msg of
>>> "input: touchscreen: add core support for Goodix Berlin Touchscreen IC"
>>>
>>> is an explanation why this is a new driver instead of adding
>>> support to the existing goodix.c code.
>>>
>>> I assume you have good reasons for this, but it would be good
>>> if you can write the reasons for this down.
>>
>> Sure, should I write it down here and/or update the commit message in a new revision ?
>>
>> Anyway, here's the reasons:
>> - globally the event handling "looks like" the current goodix.c, but again the offsets
>> are again different and none of the register address are the same, and unlike the current
>> support all registers are provided by the "ic_info" structure
>> - while with the current code it *could* be possible to merge it, with a lot of changes,
>> the firmware management looks really different, and it would be really hard to merge.
>>
>> But I may be wrong, and may be misleaded by the goodix driver structure (even if it
>> went through a really heavy cleaning process).
>>
>> Globally it seems they tried to match the "event handling" process of the previous
>> generations, but the firmware interface is completely different.
> 
> It is not unprecedented for drivers to share event processing and
> implement several ways/generations of firmware update mechanisms.

Thanks for your reply, I'm perfectly aware of that, this is why I posted
this as RFC.

If the event handling is vaguely similar, I'm not sure it's worth refactoring the
current driver since I do not have the old and current IC datasheet nor
HW to check for current support non-regression.

What I'm sure is that not a single register address, flag or struct is even close
to the current upstream defined ones.

Neil

> 
> Thanks.
>