netdev - Re: [PATCH net-next] mdio_bus: Remove unneeded gpiod NULL check

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Date:   Tue, 18 Jul 2017 15:32:09 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Fabio Estevam <festevam@...il.com>,
        Linus Walleij <linus.walleij@...aro.org>
Cc:     Sergei Shtylyov <sergei.shtylyov@...entembedded.com>,
        "David S. Miller" <davem@...emloft.net>,
        Florian Fainelli <f.fainelli@...il.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Fabio Estevam <fabio.estevam@....com>
Subject: Re: [PATCH net-next] mdio_bus: Remove unneeded gpiod NULL check

On Tue, Jul 18, 2017 at 09:52:51AM -0300, Fabio Estevam wrote:
> On Tue, Jul 18, 2017 at 9:48 AM, Sergei Shtylyov
> <sergei.shtylyov@...entembedded.com> wrote:
> > On 07/18/2017 03:39 PM, Fabio Estevam wrote:
> >
> >>>    Won't this result in kernel WARNING when GPIO is disabled?
> >
> >
> >    GPIO support, I was going to type...
> >
> >> Not sure if I understood your point, but gpiod_set_value_cansleep() is
> >> a no-op when the gpiod is NULL.
> >
> >
> >    Look at the stub in <linux/gpio/consumer.h>, it has WARN_ON(1).
> 
> This patch does not alter the behavior of the driver with respect to
> GPIO being disabled, so I still do not understand your concern.

http://elixir.free-electrons.com/linux/latest/source/include/linux/gpio/consumer.h#L345
static inline void gpiod_set_value_cansleep(struct gpio_desc *desc, int value)
{
	/* GPIO can never have been requested */
	WARN_ON(1);
}

But i would say this is a gpio problem. If GPIO enabled does not care,
GPIO disabled should also not care.

Adding Linus Walleij.

     Andrew