linux-kernel - Re: [PATCH net-next] mdio_bus: Fix PTR_ERR() usage after initialization to constant

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Message-ID: <20190201042411.GM2217@ZenIV.linux.org.uk>
Date:   Fri, 1 Feb 2019 04:24:11 +0000
From:   Al Viro <viro@...iv.linux.org.uk>
To:     YueHaibing <yuehaibing@...wei.com>
Cc:     Andrew Lunn <andrew@...n.ch>, davem@...emloft.net,
        f.fainelli@...il.com, hkallweit1@...il.com,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH net-next] mdio_bus: Fix PTR_ERR() usage after
 initialization to constant

On Tue, Jan 29, 2019 at 11:30:27AM +0800, YueHaibing wrote:
> >>  		gpiod = fwnode_get_named_gpiod(&mdiodev->dev.of_node->fwnode,
> >>  					       "reset-gpios", 0, GPIOD_OUT_LOW,
> >>  					       "PHY reset");
> >> -	if (PTR_ERR(gpiod) == -ENOENT ||
> >> -	    PTR_ERR(gpiod) == -ENOSYS)
> >> -		gpiod = NULL;
> >> -	else if (IS_ERR(gpiod))
> >> -		return PTR_ERR(gpiod);
> >> +	if (IS_ERR(gpiod)) {
> >> +		ret = PTR_ERR(gpiod);
> >> +		if (ret == -ENOENT || ret == -ENOSYS)
> >> +			gpiod = NULL;
> >> +		else
> >> +			return ret;
> >> +	}

Rule of the thumb: PTR_ERR(p) == -E... is almost always better off
as p == ERR_PTR(-E...)