linux-kernel - Re: [PATCH 38/42] drivers: gpio: vr41xx: use devm_platform_ioremap

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Date:   Tue, 12 Mar 2019 12:37:32 +0100
From:   Thierry Reding <thierry.reding@...il.com>
To:     "Enrico Weigelt, metux IT consult" <info@...ux.net>
Cc:     linux-kernel@...r.kernel.org, linus.walleij@...aro.org,
        bgolaszewski@...libre.com, andrew@...id.au, f.fainelli@...il.com,
        sbranden@...adcom.com, bcm-kernel-feedback-list@...adcom.com,
        hoan@...amperecomputing.com, orsonzhai@...il.com,
        baolin.wang@...aro.org, zhang.lyra@...il.com,
        keguang.zhang@...il.com, vz@...ia.com, matthias.bgg@...il.com,
        grygorii.strashko@...com, ssantosh@...nel.org, khilman@...nel.org,
        robert.jarzmik@...e.fr, yamada.masahiro@...ionext.com,
        jun.nie@...aro.org, shawnguo@...nel.org,
        linux-gpio@...r.kernel.org, linux-mips@...r.kernel.org,
        linux-pwm@...r.kernel.org, linux-omap@...r.kernel.org,
        linux-tegra@...r.kernel.org
Subject: Re: [PATCH 38/42] drivers: gpio: vr41xx: use
 devm_platform_ioremap_resource()

On Mon, Mar 11, 2019 at 07:55:17PM +0100, Enrico Weigelt, metux IT consult wrote:
> Use the new helper that wraps the calls to platform_get_resource()
> and devm_ioremap_resource() together.
> 
> this driver deserves a bit more cleanup, to get rid of the global
> variable giu_base, which makes it single-instance-only.
> 
> Signed-off-by: Enrico Weigelt, metux IT consult <info@...ux.net>
> ---
>  drivers/gpio/gpio-vr41xx.c | 19 +++++--------------
>  1 file changed, 5 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/gpio/gpio-vr41xx.c b/drivers/gpio/gpio-vr41xx.c
> index b13a49c..98cd715 100644
> --- a/drivers/gpio/gpio-vr41xx.c
> +++ b/drivers/gpio/gpio-vr41xx.c
> @@ -467,10 +467,9 @@ static int vr41xx_gpio_to_irq(struct gpio_chip *chip, unsigned offset)
>  
>  static int giu_probe(struct platform_device *pdev)
>  {
> -	struct resource *res;
>  	unsigned int trigger, i, pin;
>  	struct irq_chip *chip;
> -	int irq, ret;
> +	int irq;
>  
>  	switch (pdev->id) {
>  	case GPIO_50PINS_PULLUPDOWN:
> @@ -489,21 +488,14 @@ static int giu_probe(struct platform_device *pdev)
>  		return -ENODEV;
>  	}
>  
> -	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> -	if (!res)
> -		return -EBUSY;
> -
> -	giu_base = ioremap(res->start, resource_size(res));
> -	if (!giu_base)
> -		return -ENOMEM;
> +	giu_base = devm_platform_ioremap_resource(pdev, 0);
> +	if (IS_ERR(giu_base))
> +		return PTR_ERR(giu_base);

The driver currently doesn't request the memory described in the
resource, so technically you're changing behaviour here and with your
change the driver could now fail if somebody else has already claimed
the memory.

Looking at arch/mips/vr41xx there doesn't seem to be an overlap between
the memory region used by the GIU device and any others, so this should
be safe. Not sure anyone still has hardware for this around to give it
a spin.

Thierry

>  
>  	vr41xx_gpio_chip.parent = &pdev->dev;
>  
> -	ret = gpiochip_add_data(&vr41xx_gpio_chip, NULL);
> -	if (!ret) {
> -		iounmap(giu_base);
> +	if (gpiochip_add_data(&vr41xx_gpio_chip, NULL))
>  		return -ENODEV;
> -	}
>  
>  	giu_write(GIUINTENL, 0);
>  	giu_write(GIUINTENH, 0);
> @@ -534,7 +526,6 @@ static int giu_probe(struct platform_device *pdev)
>  static int giu_remove(struct platform_device *pdev)
>  {
>  	if (giu_base) {
> -		iounmap(giu_base);
>  		giu_base = NULL;
>  	}
>  
> -- 
> 1.9.1
> 

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