linux-kernel - Re: [PATCH v2 03/10] dt-bindings: sound: Add new reset compatible for sun4i-i2s

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Date:   Wed, 18 Jan 2017 08:20:34 +1100
From:   Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>
To:     Icenowy Zheng <icenowy@...c.xyz>
Cc:     Mylène Josserand 
        <mylene.josserand@...e-electrons.com>, mturquette@...libre.com,
        lgirdwood@...il.com, broonie@...nel.org, perex@...ex.cz,
        sboyd@...eaurora.org, maxime.ripard@...e-electrons.com,
        tiwai@...e.com, linux-clk@...r.kernel.org,
        linux-kernel@...r.kernel.org, mark.rutland@....com,
        devicetree@...r.kernel.org, alsa-devel@...a-project.org,
        alexandre.belloni@...e-electrons.com,
        linux-arm-kernel@...ts.infradead.org, linux-sunxi@...glegroups.com,
        wens@...e.org, robh+dt@...nel.org
Subject: Re: [PATCH v2 03/10] dt-bindings: sound: Add new reset compatible
 for sun4i-i2s

Hello,

On Wed, 18 Jan 2017 01:10:00 +0800, Icenowy Zheng wrote:

> > Add a new compatible for sun4i-i2s driver to handle some
> > SoCs that have a reset line that must be asserted/deasserted.
> >
> > This new compatible, "allwinner,sun6i-a31-i2s", requires two
> > properties:
> > - resets: phandle to the reset line
> > - reset-names: the name of the reset line ("rst").
> > Except these differences, the compatible is identical to previous one
> > which will not handle a reset line.  
> 
> But I think the IP block is identical, right?
> 
> Should a new compatible be added only for reset-line?

Having a different compatible in this case allows to make some stricter
error checking: the driver can make sure that if the compatible string
is sun6i-a31-i2s there *IS* a reset line specified in the DT. Without a
separate compatible value, such a check is not possible, and the reset
line is just optional. This can lead to people being confused if they
forget to specify the reset line.

Thomas
-- 
Thomas Petazzoni, CTO, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com