linux-kernel - Re: [PATCH v2 2/2] Input: edt-ft5x06

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Message-ID: <CAHp75VdA_peJBWXFWSs-vDxA86y6MG0J7ixzXExqDxJJzfJ7mA@mail.gmail.com>
Date: Fri, 26 Apr 2024 16:51:59 +0300
From: Andy Shevchenko <andy.shevchenko@...il.com>
To: Andreas Kemnade <andreas@...nade.info>
Cc: Felix Kaechele <felix@...chele.ca>, dmitry.torokhov@...il.com, robh+dt@...nel.org, 
	krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org, 
	o.rempel@...gutronix.de, u.kleine-koenig@...gutronix.de, hdegoede@...hat.com, 
	ye.xingchen@....com.cn, p.puschmann@...onex.com, linux-input@...r.kernel.org, 
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, 
	caleb.connolly@...aro.org
Subject: Re: [PATCH v2 2/2] Input: edt-ft5x06 - add ft5426

On Fri, Apr 26, 2024 at 10:56 AM Andreas Kemnade <andreas@...nade.info> wrote:
> On Thu, 25 Apr 2024 22:54:13 -0400
> Felix Kaechele <felix@...chele.ca> wrote:
> > On 2024-04-25 12:54, Andreas Kemnade wrote:
> > > On Fri, 5 Apr 2024 20:21:19 +0300
> > > Andy Shevchenko <andy.shevchenko@...il.com> wrote:
> > >> On Fri, Apr 5, 2024 at 7:28 PM Andreas Kemnade <andreas@...nade.info> wrote: >>> On Fri, 5 Apr 2024 18:13:45 +0300
> > >>> Andy Shevchenko <andy.shevchenko@...il.com> wrote:

..

> > >>>> Why a different vendor prefix?
> >
> > >>> I sorted by the numbers. Looking at datasheets for other controllers I see >>> https://www.displayfuture.com/Display/datasheet/controller/FT5x06.pdf
> > >>> it only mentions FocalTech Systems Co., Ltd.
> > >>
> > >> But does the driver use that? AFAICS it uses edt. Perhaps it's due to
> > >> a business split, not to my knowledge anyway.
> >
> > I've been looking into this over the past few weeks as I was working on
> > mainline support for an Android device.
> > And please forgive me if any of the following is not fully accurate, I'm
> > not an industry expert.
> >
> > After some research, my understanding of this is as follows:
> >
> > - There are companies that make touch ICs, LCD driver ICs and sometimes
> > even ICs that are both. Focaltech or Himax are examples of such companies.
> >
> > - There are companies that make LCMs. These are complete assemblies of
> > panel, backlight, touch layer and driver circuitry PCBs. This is what
> > OEMs generally purchase when they design a consumer device. Emerging
> > Display Technologies Corp. (EDT) is such a LCM manufacturing company.
> > More often than not LCM manufacturers do not make their own driver ICs.
> >
> > LCM manufacturers include ICs from Focaltech in their LCMs.
> > To my knowledge Focaltech is not a manufacturer of LCMs.
> >
> > As such, an interpretation of the compatible string "edt,edt-ft5406"
> > could be: Unspecified EDT LCM with Focaltech FT5406 IC.
> >
> >  From my perspective, more correct would either be something like
> > "edt,etm070001bdh6" (the LCM by EDT that contains this IC, especially if
> > it had model specific quirks) or "focaltech,ft5406".
> > But "edt,edt-ft5406" is incorrect if being specific is the goal here.
> > Given that the driver predates much of the DT binding rigour it's what
> > we have now though.
> >
> I think focaltech,ft5406 is better because it is consistent with other drivers/
> bindings. We do not specify the display it is used on on other touchscreen
> bindings. We do not specify the actual LEDs behind a LED interface chip.
> And often the chip name is more easily to find out than the name of a
> display.

I'm _not_ a DT person, you should clarify this with them. I just
pointed out the possible mistake (from Linux / DT perspective), and
not hardware / business related one. If they are fine with focaltech
prefix, then it's fine to me as well!

-- 
With Best Regards,
Andy Shevchenko