linux-kernel - Re: [PATCH v2 1/2] devicetree: i2c-hid: Add Wacom digitizer + regulator support

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Message-ID: <alpine.LNX.2.00.1612091532240.16984@cbobk.fhfr.pm>
Date:   Fri, 9 Dec 2016 15:36:27 +0100 (CET)
From:   Jiri Kosina <jikos@...nel.org>
To:     Rob Herring <robh@...nel.org>
cc:     Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Benjamin Tissoires <benjamin.tissoires@...hat.com>,
        Doug Anderson <dianders@...omium.org>,
        Brian Norris <briannorris@...omium.org>,
        Caesar Wang <wxt@...k-chips.com>,
        "open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>,
        "linux-input@...r.kernel.org" <linux-input@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Mark Rutland <mark.rutland@....com>
Subject: Re: [PATCH v2 1/2] devicetree: i2c-hid: Add Wacom digitizer +
 regulator support

On Thu, 8 Dec 2016, Rob Herring wrote:

> > And if tomorrow there is Elan device that is drop-in compatible (same 
> > connector, etc) with Wacom i2c-hid, will you ask for Elan-specific 
> > binding? Atmel? Weida? They all need to be powered up ultimately.
> 
> Yes, I will. 

What advantage does that bring?

> That in no way means the OS driver has to know about each and every one. 
> If they can all claim compatibility with Wacom (including power 
> control), then they can have a Wacom compatible string too. Or you can 
> just never tell me that there's a different manufacturer and I won't 
> care as long you don't need different control. But soon as a device 
> needs another power rail, GPIO or different timing, then you'd better 
> have a new compatible string.

Again, I simply don't understand what advantage does the aproach you are 
trying to use bring.

HID over I2C is a generic protocol. Sure, we need to have quirks for 
device-specific bugs, and in such cases enumerate particular devices. But 
we don't need DT for that at all.

-- 
Jiri Kosina
SUSE Labs