linux-kernel - Re: [PATCH v2] net: mdio: switch to using gpiod_get

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Date:   Sat, 14 Sep 2019 23:05:24 -0700
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        Heiner Kallweit <hkallweit1@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Linus Walleij <linus.walleij@...aro.org>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] net: mdio: switch to using gpiod_get_optional()

On Sat, Sep 14, 2019 at 08:09:33PM +0300, Andy Shevchenko wrote:
> On Fri, Sep 13, 2019 at 03:55:47PM -0700, Dmitry Torokhov wrote:
> > The MDIO device reset line is optional and now that gpiod_get_optional()
> > returns proper value when GPIO support is compiled out, there is no
> > reason to use fwnode_get_named_gpiod() that I plan to hide away.
> > 
> > Let's switch to using more standard gpiod_get_optional() and
> > gpiod_set_consumer_name() to keep the nice "PHY reset" label.
> > 
> > Also there is no reason to only try to fetch the reset GPIO when we have
> > OF node, gpiolib can fetch GPIO data from firmwares as well.
> > 
> 
> Reviewed-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>

Thanks Andy.

> 
> But see comment below.
> 

> > +	mdiodev->reset_gpio = gpiod_get_optional(&mdiodev->dev,
> > +						 "reset", GPIOD_OUT_LOW);
> > +	error = PTR_ERR_OR_ZERO(mdiodev->reset_gpio);
> > +	if (error)
> > +		return error;
> > +
> 
> > +	if (mdiodev->reset_gpio)
> 
> This is redundant check.

I see that gpiod_* API handle NULL desc and usually return immediately,
but frankly I am not that comfortable with it. I'm OK with functions
that free/destroy objects that recognize NULL resources, but it is
unusual for other types of APIs.

Thanks.

-- 
Dmitry