Re: [RESEND PATCH v2 3/3] ARM: dts: imx28-cfa10036: Fix the reset gpio signal polarity

From: "Vokáč Michal" <Michal.Vokac@ysoft.com>
To: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
	Shawn Guo <shawnguo@kernel.org>
Cc: Fabio Estevam <fabio.estevam@nxp.com>,
	Rob Herring <robh+dt@kernel.org>,
	"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"linux-fbdev@vger.kernel.org" <linux-fbdev@vger.kernel.org>
Subject: Re: [RESEND PATCH v2 3/3] ARM: dts: imx28-cfa10036: Fix the reset gpio signal polarity
Date: Tue, 9 Oct 2018 08:29:08 +0000	[thread overview]
Message-ID: <bfbfd490-3872-2fd9-e088-3add596b987c@ysoft.com> (raw)
In-Reply-To: <20181009075145eucas1p2691c7d04aa8328080af7cbc4ab5e03b9~b4WFAVFkx0235802358eucas1p2c@eucas1p2.samsung.com>

On 9.10.2018 09:51, Bartlomiej Zolnierkiewicz wrote:
> 
> On 10/09/2018 02:20 AM, Shawn Guo wrote:
>> On Mon, Oct 08, 2018 at 11:45:36AM +0000, Vokáč Michal wrote:
>>> On 27.9.2018 11:24, Michal Vokáč wrote:
>>>> The reset signal of the SSD1306 OLED display is actually active-low.
>>>> Adapt the DT to reflect the real world.
>>>>
>>>> Signed-off-by: Michal Vokáč <michal.vokac@ysoft.com>
>>>> ---
>>>> v2 changes: New patch in the series
>>>
>>> Bartlomiej just queued the first two patches for v4.20.
>>> Will somebody take this one? Otherwise this SoM will end up with
>>> broken OLED display reset.
>>
>> Well, it means the change breaks the ABI between kernel and device tree,
>> e.g. the new kernel will not work with existing/installed DTBs.
> 
> Should I revert this sdd10307fb patch then?

Sorry for the inconvenience :( Lesson learned..

So in other words (no offense): broken drivers need to stay broken because
users may already get used to the broken behavior?

Personally I would not describe this change as a device tree ABI change.
It is not a change in the DT binding. Or are "stable device tree API" and
"device tree ABI" really two different things?

The first patch should be OK though.

Michal