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

[Neil Armstrong]

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.