linux-kernel - Re: linux-next: manual merge of the arm-soc tree with the i2c-embedded tree

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Message-ID: <20120718095937.GB22739@opensource.wolfsonmicro.com>
Date:	Wed, 18 Jul 2012 10:59:37 +0100
From:	Mark Brown <broonie@...nsource.wolfsonmicro.com>
To:	Shawn Guo <shawn.guo@...escale.com>
Cc:	Lee Jones <lee.jones@...aro.org>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	Linus Walleij <linus.walleij@...ricsson.com>,
	devicetree-discuss@...ts.ozlabs.org,
	Wolfram Sang <w.sang@...gutronix.de>,
	linux-kernel@...r.kernel.org, Deepak Saxena <dsaxena@...aro.org>,
	linux-next@...r.kernel.org, Alessandro Rubini <rubini@...dd.com>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: linux-next: manual merge of the arm-soc tree with the
 i2c-embedded tree

On Wed, Jul 18, 2012 at 01:33:42PM +0800, Shawn Guo wrote:

> I have an IP block getting different FIFO size on different IMX SoCs.
> We could introduce a new compatible string for driver to figure it out,
> but I think the simpler way is just have the data encoded in device
> tree.  In any case DT is not completely limited in encoding board
> specific data.  Today, we have IO region and interrupt number of
> hardware blocks encoded in DT, and to me, FIFO size could just be
> another aspect of hardware block we could choose to encode in DT.

So, this is part of the problem with encoding the description of the SoC
into the DT - we're not doing a good job of splitting out the silicon
description from the board specific description which is not a triumph
for maintainability since it means that we end up needing to modify the
DT for every board using the silicon if we want to use the new feature
(assuming people maintain binary compatibility with old DTs, which we
don't do a good job at either even for established DT architectures).

It's not the using device tree bit that creates concern for me here,
it's the fact that the board and silicon aren't being separated.

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