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

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Date:   Mon, 12 Dec 2016 11:01:10 +0100
From:   Benjamin Tissoires <benjamin.tissoires@...hat.com>
To:     Jiri Kosina <jikos@...nel.org>
Cc:     Rob Herring <robh@...nel.org>,
        Dmitry Torokhov <dmitry.torokhov@...il.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 Dec 12 2016 or thereabouts, Jiri Kosina wrote:
> Given the timing (merge window being open) and given then NACK given by 
> Rob, I've now unapplied the patches (the for-4.10/i2c-hid branch is now 
> obsolete, and has been superseded by for-4.10/i2c-hid-nopower).
> 
> However, this is mostly done in order to provide more time for discussion; 
> I still disagree with the reasoning behind the NACK.
> 

To hopefully make things going forward a little bit, I was wondering
over the week-end if we should not solve this particular issue by adding
an intermediate platform DT node:

instead of having:
---
	i2c-hid-dev@2c {
		compatible = "hid-over-i2c";
		reg = <0x2c>;
		hid-descr-addr = <0x0020>;
		interrupt-parent = <&gpx3>;
		interrupts = <3 2>;
		vdd-supply = <sth>;
		init-delay-ms = <100>;
	};
---

we would have:
---
	platform-i2c-hid@01 {
		compatible = "very-special-board-that-needs-firmware-quirks-and-delay-of-100ms";
		vdd-supply = <sth>;
		i2c-hid-dev@2c {
			compatible = "hid-over-i2c";
			reg = <0x2c>;
			hid-descr-addr = <0x0020>;
			interrupt-parent = <&gpx3>;
			interrupts = <3 2>;
                };
	};
---

If I am not wrong, the platform device should be initialized before
i2c-hid get called, which allows to setup properly the vdd supply.
On resume/suspend, the tree should be respected and we should be able to
enable/disable power in the same fashion this patch provides.

We could then extend this platform device at will without tinkering in
i2c-hid and we could also handle the GPIOs, reset or whatever is
required in the future through compatibles.

Thoughts? yes? no? bullshit?

Cheers,
Benjamin