linux-kernel - Re: [PATCH] of: match the compatible in the order set by the dts file

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Message-ID: <51DC1DB4.3050802@wwwdotorg.org>
Date:	Tue, 09 Jul 2013 08:27:00 -0600
From:	Stephen Warren <swarren@...dotorg.org>
To:	Sascha Hauer <s.hauer@...gutronix.de>
CC:	Huang Shijie <b32955@...escale.com>, grant.likely@...aro.org,
	devicetree-discuss@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
	rob.herring@...xeda.com, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] of: match the compatible in the order set by the dts
 file

On 07/09/2013 01:05 AM, Sascha Hauer wrote:
> On Fri, Jul 05, 2013 at 04:43:38PM +0800, Huang Shijie wrote:
>> If we set the uart compatible in the dts file like this:
>>    ------------------------------------------------------
>>     compatible = "fsl,imx6q-uart", "fsl,imx21-uart";
>>    ------------------------------------------------------
>>
>> and we set the uart compatible in the uart driver like this:
>>    ------------------------------------------------------
>> 	{ .compatible = "fsl,imx1-uart", ... },
>> 	{ .compatible = "fsl,imx21-uart", ... },
>> 	{ .compatible = "fsl,imx6q-uart", ... },
>> 	{ /* sentinel */ }
>>    ------------------------------------------------------
>>
>> the current code will match the "fsl,imx21-uart" in the end.
>>
>> Of course, this is not what we want. We want it to match the "fsl,imx6q-uart".
>>
>> This patch rewrites the match code, and make it to check the compatible
>> in the order set by the DTS file.
> 
> Why don't you set the matching order in the driver the way you want it
> to be, i.e.:
> 
> 	{ .compatible = "fsl,imx6q-uart", ... },
> 	{ .compatible = "fsl,imx21-uart", ... },
> 	{ .compatible = "fsl,imx1-uart", ... },

DT semantics are that earlier entries in the compatible property are
supposed to be matched first, irrespective of how the driver is constructed.

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