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Subject: Re: [PATCH v2] gpiolib: Take MUX usage into account
To:     Ramon Fried <ramon.fried@linux.intel.com>,
        linus.walleij@linaro.org, bgolaszewski@baylibre.com
Cc:     linux-gpio@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20190813014210.15519-1-ramon.fried@linux.intel.com>
Reply-To: Stefan Wahren <wahrenst@gmx.net>
From:   Stefan Wahren <stefan.wahren@i2se.com>
Message-ID: <1650c967-5176-70db-ff9a-b2af432ba1e7@i2se.com>
Date:   Tue, 13 Aug 2019 07:38:38 +0200
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Hi Ramon,

On 13.08.19 03:42, Ramon Fried wrote:
> From: Stefan Wahren <stefan.wahren@i2se.com>
>
> The user space like gpioinfo only see the GPIO usage but not the
> MUX usage (e.g. I2C or SPI usage) of a pin. As a user we want to know which
> pin is free/safe to use. So take the MUX usage of strict pinmux controllers
> into account to get a more realistic view for ioctl GPIO_GET_LINEINFO_IOCTL.
>
> Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
> Tested-by: Ramon Fried <rfried.dev@gmail.com>
> Signed-off-by: Ramon Fried <rfried.dev@gmail.com>
> ---
> v2: Address review from linus:
> * ** Please notive logic was reversed **
> * renamed pinctrl_gpio_is_in_use() to pinctrl_gpio_can_use_line()
> * renamed pinmux_is_in_use() to pinmux_can_be_used_for_gpio()
> * changed dev_err to dev_dbg (Linus suggested removing it altogether, I
>   find it better to keep it for debug).
thanks for taking care of this.
>
>  drivers/gpio/gpiolib.c           |  3 ++-
>  drivers/pinctrl/core.c           | 28 ++++++++++++++++++++++++++++
>  drivers/pinctrl/pinmux.c         | 27 +++++++++++++++++++++++++++
>  drivers/pinctrl/pinmux.h         |  8 ++++++++
>  include/linux/pinctrl/consumer.h |  6 ++++++
>  5 files changed, 71 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
> index f497003f119c..52937bf8e514 100644
> --- a/drivers/gpio/gpiolib.c
> +++ b/drivers/gpio/gpiolib.c
> @@ -1084,7 +1084,8 @@ static long gpio_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
>  		    test_bit(FLAG_IS_HOGGED, &desc->flags) ||
>  		    test_bit(FLAG_USED_AS_IRQ, &desc->flags) ||
>  		    test_bit(FLAG_EXPORT, &desc->flags) ||
> -		    test_bit(FLAG_SYSFS, &desc->flags))
> +		    test_bit(FLAG_SYSFS, &desc->flags) ||
> +		    !pinctrl_gpio_can_use_line(chip->base + lineinfo.line_offset))
>  			lineinfo.flags |= GPIOLINE_FLAG_KERNEL;
>  		if (test_bit(FLAG_IS_OUT, &desc->flags))
>  			lineinfo.flags |= GPIOLINE_FLAG_IS_OUT;
> diff --git a/drivers/pinctrl/core.c b/drivers/pinctrl/core.c
> index b70df27874d1..2bbd8ee93507 100644
> --- a/drivers/pinctrl/core.c
> +++ b/drivers/pinctrl/core.c
> @@ -736,6 +736,34 @@ int pinctrl_get_group_selector(struct pinctrl_dev *pctldev,
>  	return -EINVAL;
>  }
>  
> +bool pinctrl_gpio_can_use_line(unsigned gpio)
> +{
> +	struct pinctrl_dev *pctldev;
> +	struct pinctrl_gpio_range *range;
> +	bool result;
> +	int pin;
> +
> +	/*
> +	 * Try to obtain GPIO range, if it fails
> +	 * we're probably dealing with GPIO driver
> +	 * without a backing pin controller - bail out.
> +	 */
> +	if (pinctrl_get_device_gpio_range(gpio, &pctldev, &range))
> +		return true;
> +
> +	mutex_lock(&pctldev->mutex);
> +
> +	/* Convert to the pin controllers number space */
> +	pin = gpio_to_pin(range, gpio);
> +
> +	result = pinmux_can_be_used_for_gpio(pctldev, pin);
> +
> +	mutex_unlock(&pctldev->mutex);
> +
> +	return result;
> +}
> +EXPORT_SYMBOL_GPL(pinctrl_gpio_can_use_line);
> +
>  /**
>   * pinctrl_gpio_request() - request a single pin to be used as GPIO
>   * @gpio: the GPIO pin number from the GPIO subsystem number space
> diff --git a/drivers/pinctrl/pinmux.c b/drivers/pinctrl/pinmux.c
> index 020e54f843f9..7e42a5738d82 100644
> --- a/drivers/pinctrl/pinmux.c
> +++ b/drivers/pinctrl/pinmux.c
> @@ -70,6 +70,33 @@ int pinmux_validate_map(const struct pinctrl_map *map, int i)
>  	return 0;
>  }
>  
> +/**
> + * pinmux_can_be_used_for_gpio() - check if a specific pin
> + *	is either muxed to a different function or used as gpio.
> + *
> + * @pin: the pin number in the global pin space
> + *
> + * Controllers not defined as strict will always return true,
> + * menaning that the gpio can be used.
> + */
> +bool pinmux_can_be_used_for_gpio(struct pinctrl_dev *pctldev, unsigned pin)
> +{
> +	struct pin_desc *desc = pin_desc_get(pctldev, pin);
> +	const struct pinmux_ops *ops = pctldev->desc->pmxops;
> +
> +	if (!desc) {
> +		dev_dbg(pctldev->dev,
> +			"pin %u is not registered so it cannot be requested\n",
> +			pin);
> +		return true;

This return value looks strange to me.

Stefan