linux-kernel - Re: [PATCH v2 1/3] serial: mctrl_gpio: Avoid probe failures in case of missing gpiolib

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Message-ID: <20190801203316.7ntlv6hequmddfxu@pengutronix.de>
Date:   Thu, 1 Aug 2019 22:33:16 +0200
From:   Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
To:     Schrempf Frieder <frieder.schrempf@...tron.de>
Cc:     "shawnguo@...nel.org" <shawnguo@...nel.org>,
        "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        "festevam@...il.com" <festevam@...il.com>,
        "linux-imx@....com" <linux-imx@....com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "geert+renesas@...der.be" <geert+renesas@...der.be>,
        Jiri Slaby <jslaby@...e.com>,
        "linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 1/3] serial: mctrl_gpio: Avoid probe failures in case
 of missing gpiolib

On Thu, Aug 01, 2019 at 06:45:21PM +0000, Schrempf Frieder wrote:
> From: Frieder Schrempf <frieder.schrempf@...tron.de>
> 
> If CONFIG_GPIOLIB is not enabled, mctrl_gpio_init() and
> mctrl_gpio_init_noauto() will currently return an error pointer with
> -ENOSYS. As the mctrl GPIOs are usually optional, drivers need to
> check for this condition to allow continue probing.
> 
> To avoid the need for this check in each driver, we return NULL
> instead, as all the mctrl_gpio_*() functions are skipped anyway.
> We also adapt mctrl_gpio_to_gpiod() to be in line with this change.
> 
> Signed-off-by: Frieder Schrempf <frieder.schrempf@...tron.de>
> Reviewed-by: Fabio Estevam <festevam@...il.com>

nitpick: put your S-o-b last.

> ---
> Changes in v2
> =============
> * Move the sh_sci changes to a separate patch
> * Add a patch for the 8250 driver
> * Add Fabio's R-b tag
> ---
>  drivers/tty/serial/serial_mctrl_gpio.c | 3 +++
>  drivers/tty/serial/serial_mctrl_gpio.h | 6 +++---
>  2 files changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/tty/serial/serial_mctrl_gpio.c b/drivers/tty/serial/serial_mctrl_gpio.c
> index 2b400189be91..54c43e02e375 100644
> --- a/drivers/tty/serial/serial_mctrl_gpio.c
> +++ b/drivers/tty/serial/serial_mctrl_gpio.c
> @@ -61,6 +61,9 @@ EXPORT_SYMBOL_GPL(mctrl_gpio_set);
>  struct gpio_desc *mctrl_gpio_to_gpiod(struct mctrl_gpios *gpios,
>  				      enum mctrl_gpio_idx gidx)
>  {
> +	if (gpios == NULL)
> +		return NULL;
> +

I wonder why you need this. If GPIOLIB is off this code isn't active and
with GPIOLIB calling mctrl_gpio_to_gpiod with a gpios == NULL is a bug
that IMHO should not be silently ignored.

Am I missing something (again)?

>  	return gpios->gpio[gidx];
>  }

Best regards
Uwe

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