From mboxrd@z Thu Jan 1 00:00:00 1970 From: robh@kernel.org (Rob Herring) Date: Wed, 18 Jan 2017 16:20:10 -0600 Subject: [PATCH v1 2/2] arm: dts: mt2701: add nor flash node In-Reply-To: <20170117143650.5db87148@free-electrons.com> References: <20170113172825.75d545a3@bbrezillon> <86c997be-f500-eaa1-3ba5-d21cff6223b7@gmail.com> <20170113175628.1793f433@bbrezillon> <0fafcd8d-cf99-de6b-728f-5e3637810b68@gmail.com> <20170114092958.022f2fc8@bbrezillon> <20170116094032.6f471f11@bbrezillon> <20170117143650.5db87148@free-electrons.com> Message-ID: <20170118222010.ivc6jxpnrumemvdf@rob-hp-laptop> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Tue, Jan 17, 2017 at 02:36:50PM +1100, Thomas Petazzoni wrote: > Hello, > > (Side note: you guys should learn about stripping irrelevant parts of > an e-mail when replying!) > > On Mon, 16 Jan 2017 09:40:32 +0100, Boris Brezillon wrote: > > > > Well this is OK I guess, but then you can also use "mediatek,mt8173-nor" > > > as the oldest supported compatible and be done with it, no ? It looks a > > > bit crappy though, I admit that ... > > > > Let's stop bikeshedding and wait for DT maintainers feedback > > before taking a decision ;-). > > > > Rob, Mark, any opinion? > Sigh, is how to do compatibles really not yet understood? > I agree that a clarification would be good. There are really two > options: > > 1. Have two compatible strings in the DT, the one that matches the > exact SoC where the IP is found (first compatible string) and the > one that matches some other SoC where the same IP is found (second > compatible string). Originally, Linux only supports the second > compatible string in its device driver, but if it happens that a > difference is found between two IPs that we thought were the same, > we can add support for the first compatible string in the driver, > with a slightly different behavior. This. And no wildcards in the compatible string. > 2. Have a single compatible string in the DT, matching the exact SoC > where the IP is found. This involves adding immediately this > compatible string in the corresponding driver. I wouldn't object to this from a DT perspective as I have no clue generally if IP blocks are "the same" or not. Subsystem maintainers will object though. > I've not really been able to figure out which of the two options is the > most future-proof/appropriate. They are both future-proof. #2 has the disadvantage of requiring a kernel update for a new SoC. Rob