netdev - Re: [PATCH] net: phy: at803x: don't depend on GPIOLIB

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Message-ID: <20160318125455.GN4292@pengutronix.de>
Date:	Fri, 18 Mar 2016 13:54:55 +0100
From:	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
To:	Sebastian Frias <sf84@...oste.net>
Cc:	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
	lkml <linux-kernel@...r.kernel.org>, mason <slash.tmp@...e.fr>,
	Daniel Mack <daniel@...que.org>,
	Florian Fainelli <f.fainelli@...il.com>,
	Mans Rullgard <mans@...sr.com>,
	Fabio Estevam <festevam@...il.com>,
	Martin Blumenstingl <martin.blumenstingl@...il.com>,
	Linus Walleij <linus.walleij@...aro.org>
Subject: Re: [PATCH] net: phy: at803x: don't depend on GPIOLIB

[expand cc a bit more]

Hello,

On Wed, Mar 16, 2016 at 06:25:59PM +0100, Sebastian Frias wrote:
> Commit 687908c2b649 ("net: phy: at803x: simplify using
> devm_gpiod_get_optional and its 4th argument") introduced a dependency
> on GPIOLIB that was not there before.
> 
> This commit removes such dependency by checking the return code and
> comparing it against ENOSYS which is returned when GPIOLIB is not
> selected.
> 
> Fixes: 687908c2b649 ("net: phy: at803x: simplify using devm_gpiod_get_optional and its 4th argument")
> 
> Signed-off-by: Sebastian Frias <sf84@...oste.net>
> ---
>  drivers/net/phy/at803x.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/phy/at803x.c b/drivers/net/phy/at803x.c
> index 2174ec9..88b7ff3 100644
> --- a/drivers/net/phy/at803x.c
> +++ b/drivers/net/phy/at803x.c
> @@ -252,7 +252,9 @@ static int at803x_probe(struct phy_device *phydev)
>  		return -ENOMEM;
> 
>  	gpiod_reset = devm_gpiod_get_optional(dev, "reset", GPIOD_OUT_HIGH);
> -	if (IS_ERR(gpiod_reset))
> +	if (PTR_ERR(gpiod_reset) == -ENOSYS)
> +		gpiod_reset = NULL;
> +	else if (IS_ERR(gpiod_reset))

this isn't better either (IMHO it's worse, but maybe this is debatable
and also depends on your POV).

With 687908c2b649 I made kernels without GPIOLIB fail to bind this
device. I admit this is not maximally nice.

Your change makes the driver bind in this case again and then the reset
gpio isn't handled at all which might result in a later and harder to
debug error.

The better approach to fix your problem is: make the driver depend (or
force) on GPIOLIB. Or alternatively, drop reset-handling from the
driver.

>From a driver perspecitive, it would be nice if devm_gpiod_get_optional
returned NULL iff the respective gpio isn't specified even with
GPIOLIB=n, but this isn't sensible either because it would result in
quite some gpiolib code to not being conditionally compiled on
CONFIG_GPIOLIB any more.

Best regards
Uwe

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