linux-kernel - Re: [PATCH v3 01/11] regulator: core: add API to get voltage constraints

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Message-ID: <20180208145834.GA27520@sirena.org.uk>
Date:   Thu, 8 Feb 2018 14:58:34 +0000
From:   Mark Brown <broonie@...nel.org>
To:     Laxman Dewangan <ldewangan@...dia.com>
Cc:     Peter De Schrijver <pdeschrijver@...dia.com>,
        linux-tegra@...r.kernel.org, linux-clk@...r.kernel.org,
        mturquette@...libre.com, sboyd@...eaurora.org, robh+dt@...nel.org,
        mark.rutland@....com, devicetree@...r.kernel.org,
        lgirdwood@...il.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 01/11] regulator: core: add API to get voltage
 constraints

On Thu, Feb 08, 2018 at 03:34:56PM +0530, Laxman Dewangan wrote:

> I added this API in downstream for the purpose of finding whether rail
> output can be changed or not(fixed) based on constraints.
> If min and max is same then it can not change. I used this information to
> set the pad voltage of SOC automatically.

That's a reasonable thing to want to know.  The way the API wants you to
ask that question at the minute is to check if you can set the voltages
you might want to set and then if there's only one possible voltage you
can conclude that change is not possible.  I appreciate that that's a
bit of a long way round to do it, the thinking was to try to keep the
client drivers more robust in cases you can change the voltage but not
to all the values the driver wants.  I'd consider relaxing that and
having a direct API to ask about variability (just as a boolean) since
it does occur to me that this can be a useful speedup during init but I
need to think.

> I dont know other usage when I added this API. May be Peter is needed here.

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