linux-kernel - Re: [PATCH RFC 0/4] input: touchscreen: add initial support for Goodix Berlin touchscreen IC

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Date:   Tue, 6 Jun 2023 11:44:45 -0700
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     Neil Armstrong <neil.armstrong@...aro.org>
Cc:     Hans de Goede <hdegoede@...hat.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Bastien Nocera <hadess@...ess.net>,
        Henrik Rydberg <rydberg@...math.org>,
        linux-input@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC 0/4] input: touchscreen: add initial support for
 Goodix Berlin touchscreen IC

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.

-- 
Dmitry