netdev - Re: [PATCH 3/6] net: stmmac: sun8i: Use devm_regulator

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Date:   Tue, 20 Aug 2019 17:47:14 +0200
From:   Ondřej Jirman <megous@...ous.com>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Maxime Ripard <mripard@...nel.org>,
        Chen-Yu Tsai <wens@...e.org>,
        Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        Jose Abreu <joabreu@...opsys.com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        devicetree@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        linux-stm32@...md-mailman.stormreply.com,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 3/6] net: stmmac: sun8i: Use devm_regulator_get for PHY
 regulator

Hi Andrew,

On Tue, Aug 20, 2019 at 05:39:39PM +0200, Andrew Lunn wrote:
> On Tue, Aug 20, 2019 at 04:53:40PM +0200, megous@...ous.com wrote:
> > From: Ondrej Jirman <megous@...ous.com>
> > 
> > Use devm_regulator_get instead of devm_regulator_get_optional and rely
> > on dummy supply. This avoids NULL checks before regulator_enable/disable
> > calls.
> 
> Hi Ondrej
> 
> What do you mean by a dummy supply? I'm just trying to make sure you
> are not breaking backwards compatibility.

Sorry, I mean dummy regulator. See:

https://elixir.bootlin.com/linux/latest/source/drivers/regulator/core.c#L1874

On systems that use DT (i.e. have_full_constraints() == true), when the
regulator is not found (ENODEV, not specified in DT), regulator_get will return
a fake dummy regulator that can be enabled/disabled, but doesn't do anything
real.

This can be used to avoid NULL checks and make the code simpler.

regards,
	Ondrej

>      Thanks
> 	Andrew