linux-kernel - Re: [PATCH 4.19 038/113] serial: mctrl_gpio: Check if GPIO property exisits before requesting it

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Message-ID: <20190731181923.GB821@amd>
Date:   Wed, 31 Jul 2019 20:19:23 +0200
From:   Pavel Machek <pavel@...x.de>
To:     pavel@....cz
Cc:     linux-kernel@...r.kernel.org, Stefan Roese <sr@...x.de>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Yegor Yefremov <yegorslists@...glemail.com>,
        Giulio Benetti <giulio.benetti@...ronovasrl.com>,
        Sasha Levin <sashal@...nel.org>
Subject: Re: [PATCH 4.19 038/113] serial: mctrl_gpio: Check if GPIO property
 exisits before requesting it

Hi!

> This patch implements the fix suggested by Mika in his statement above.

> @@ -12,6 +12,7 @@
>  #include <linux/termios.h>
>  #include <linux/serial_core.h>
>  #include <linux/module.h>
> +#include <linux/property.h>
>  
>  #include "serial_mctrl_gpio.h"
>  
> @@ -115,6 +116,19 @@ struct mctrl_gpios *mctrl_gpio_init_noauto(struct device *dev, unsigned int idx)
>  
>  	for (i = 0; i < UART_GPIO_MAX; i++) {
>  		enum gpiod_flags flags;
> +		char *gpio_str;
> +		bool present;
> +
> +		/* Check if GPIO property exists and continue if not */
> +		gpio_str = kasprintf(GFP_KERNEL, "%s-gpios",
> +				     mctrl_gpios_desc[i].name);
> +		if (!gpio_str)
> +			continue;

So if this fails, we'll let the system boot in different configuration
than usual. I guess GFP_KERNEL allocation failures are really rare,
but would it be worth a message? Or maybe buffer on the stack so we
don't do allocations in a loop, and so that allocation can't fail?

Thanks,
								Pavel

> +		present = device_property_present(dev, gpio_str);
> +		kfree(gpio_str);
> +		if (!present)
> +			continue;
>  
>  		if (mctrl_gpios_desc[i].dir_out)
>  			flags = GPIOD_OUT_LOW;

-- 
DENX Software Engineering GmbH,      Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany

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