linux-kernel - Re: [PATCH] of/base: Replace alias if it already exists

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Message-ID: <538D9C42.9040707@gmail.com>
Date:	Tue, 03 Jun 2014 12:58:26 +0300
From:	Ivaylo Dimitrov <ivo.g.dimitrov.75@...il.com>
To:	Grant Likely <grant.likely@...aro.org>
CC:	robh+dt@...nel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] of/base: Replace alias if it already exists



On  3.06.2014 11:53, Grant Likely wrote:

> So, if I understand correctly, the .dtsi file sets up aliases like so:
>
> aliases {
> 	i2c0 = &i2c1;
> 	i2c1 = &i2c2;
> 	i2c2 = &i2c3;
> 	i2c3 = &i2c4;
> 	i2c4 = &i2c5;
> };
>
> and the board file does this:
>
>
> aliases {
> 	i2c1 = &i2c1;
> 	i2c2 = &i2c2;
> 	i2c3 = &i2c3;
> 	i2c4 = &i2c4;
> 	i2c5 = &i2c5;
> };
>
> Which results in a dtb that looks like this:
>
> aliases {
> 	i2c0 = &i2c1;
> 	i2c1 = &i2c1;
> 	i2c2 = &i2c2;
> 	i2c3 = &i2c3;
> 	i2c4 = &i2c4;
> 	i2c5 = &i2c5;
> };
>
> Do I understand correctly?
>

I guess this is the resulting dtb, at least kernel assigns "incorrect" 
index(0) only to i2c1 bus.

> The way aliases works, it is completely valid to have multiple aliases
> pointing at the same node. There are also no ordering guarantees about
> which comes first, so though this patch might work for you at the
> moment, there is no guarantee that it will continue to do so. If the
> i2c0 alias is invalid for that platform, then it must be removed.
>

I see.

> Unfortunately, the overlays have no mechanism for removing properties at
> this time. Can you try putting the following into your board dts file
> and see if it works?
>
> aliases {
> 	i2c0;		/* Deactivate the old alias by making it blank */
> 	i2c1 = &i2c1;
> 	i2c2 = &i2c2;
> 	i2c3 = &i2c3;
> 	i2c4 = &i2c4;
> 	i2c5 = &i2c5;
> };
>
> g.
>

Will do, as soon as I get back home.

Thanks,
Ivo
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