linux-kernel - Re: [PATCH] regulator: rk808: make better use of the gpiod API

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Message-ID: <20150721143524.GD9981@pengutronix.de>
Date:	Tue, 21 Jul 2015 16:35:24 +0200
From:	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
To:	Krzysztof Kozlowski <k.kozlowski@...sung.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	Linus Walleij <linus.walleij@...aro.org>,
	Mark Brown <broonie@...nel.org>,
	Liam Girdwood <lgirdwood@...il.com>,
	linux-next@...r.kernel.org, linux-kernel@...r.kernel.org,
	Chris Zhong <zyw@...k-chips.com>, kernel@...gutronix.de
Subject: Re: [PATCH] regulator: rk808: make better use of the gpiod API

Hello,

On Tue, Jul 21, 2015 at 10:09:32PM +0900, Krzysztof Kozlowski wrote:
> 2015-07-21 15:59 GMT+09:00 Uwe Kleine-König <u.kleine-koenig@...gutronix.de>:
> > @@ -540,14 +540,19 @@ static int rk808_regulator_dt_parse_pdata(struct device *dev,
> >                 goto dt_parse_end;
> >
> >         for (i = 0; i < ARRAY_SIZE(pdata->dvs_gpio); i++) {
> > -               pdata->dvs_gpio[i] = gpiod_get_index(client_dev, "dvs", i);
> > +               pdata->dvs_gpio[i] =
> > +                       devm_gpiod_get_index_optional(client_dev, "dvs", i,
> > +                                                     GPIOD_OUT_LOW);
> >                 if (IS_ERR(pdata->dvs_gpio[i])) {
> > +                       dev_err(dev, "failed to get dvs%d gpio\n", i);
> 
> Missing of_node_put() from of_get_child_by_name() called before.
Good catch, thanks.

> > @@ -561,14 +566,6 @@ dt_parse_end:
> >
> >  static int rk808_regulator_remove(struct platform_device *pdev)
> >  {
> > -       struct rk808_regulator_data *pdata = platform_get_drvdata(pdev);
> > -       int i;
> > -
> > -       for (i = 0; i < ARRAY_SIZE(pdata->dvs_gpio); i++) {
> > -               if (!IS_ERR(pdata->dvs_gpio[i]))
> > -                       gpiod_put(pdata->dvs_gpio[i]);
> > -       }
> > -
> >         return 0;
> >  }
> 
> The function looks empty so it can be removed entirely.
I assumed that not having a remove function makes the device not
detachable. Not sure about that.
Looking at the code I found that not having a remove function can yield
surprises, though. If your driver has a probe but no remove function the
platform bus glue calls

	dev_pm_domain_attach(_dev, true);

at probe time, but not

	dev_pm_domain_detach(_dev, true);

at remove. I admit I don't know about that dev_pm_domain stuff, but it
looks wrong to only have one but not the other. Greg?

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |
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