linux-kernel - Re: [PATCH] net: dsa: lan9303: correctly check return value of devm_gpiod_get

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Date:   Mon, 13 Nov 2017 05:38:15 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     Phil Reid <preid@...ctromag.com.au>
Cc:     Pan Bian <bianpan2016@....com>,
        Vivien Didelot <vivien.didelot@...oirfairelinux.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org
Subject: Re: [PATCH] net: dsa: lan9303: correctly check return value of
 devm_gpiod_get_optional

On Mon, Nov 13, 2017 at 12:08:49PM +0800, Phil Reid wrote:
> On 12/11/2017 23:38, Pan Bian wrote:
> >Function devm_gpiod_get_optional() returns an ERR_PTR on failure. Its
> >return value should not be validated by a NULL check. Instead, use IS_ERR.
> >
> >Signed-off-by: Pan Bian <bianpan2016@....com>
> >---
> >  drivers/net/dsa/lan9303-core.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> >diff --git a/drivers/net/dsa/lan9303-core.c b/drivers/net/dsa/lan9303-core.c
> >index b471413..6d3fc8f 100644
> >--- a/drivers/net/dsa/lan9303-core.c
> >+++ b/drivers/net/dsa/lan9303-core.c
> >@@ -828,7 +828,7 @@ static void lan9303_probe_reset_gpio(struct lan9303 *chip,
> >  	chip->reset_gpio = devm_gpiod_get_optional(chip->dev, "reset",
> >  						   GPIOD_OUT_LOW);
> >-	if (!chip->reset_gpio) {
> >+	if (IS_ERR(chip->reset_gpio)) {
> >  		dev_dbg(chip->dev, "No reset GPIO defined\n");
> >  		return;
> >  	}
> >
> Should not an error actually report the error and error out (ie fail probe).
> But a null is the optional return and ok. (ie when -ENOENT return from sub gpiod_get call).
> 
> IS_ERR should be a separate condition check I think.

Hi Phil

Yes, you are right. In particular, -EPROBE_DEFFER should be propagated
up and cause the probe to fail and be called later.

Care to submit a patch?

     Andrew