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Subject[PATCH v3] gpiolib: Take MUX usage into account
Date
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>
---
v3:
* Remove the debug message and replace with comment in code.
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).
drivers/gpio/gpiolib.c | 3 ++-
drivers/pinctrl/core.c | 28 ++++++++++++++++++++++++++++
drivers/pinctrl/pinmux.c | 24 ++++++++++++++++++++++++
drivers/pinctrl/pinmux.h | 8 ++++++++
include/linux/pinctrl/consumer.h | 6 ++++++
5 files changed, 68 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..e914f6efd39e 100644
--- a/drivers/pinctrl/pinmux.c
+++ b/drivers/pinctrl/pinmux.c
@@ -70,6 +70,30 @@ 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;
+
+ /* Can't inspect pin, assume it can be used */
+ if (!desc)
+ return true;
+
+ if (ops->strict && desc->mux_usecount)
+ return false;
+
+ return !(ops->strict && !!desc->gpio_owner);
+}
+
/**
* pin_request() - request a single pin to be muxed in, typically for GPIO
* @pin: the pin number in the global pin space
diff --git a/drivers/pinctrl/pinmux.h b/drivers/pinctrl/pinmux.h
index 794cb3a003ff..78c3a31be882 100644
--- a/drivers/pinctrl/pinmux.h
+++ b/drivers/pinctrl/pinmux.h
@@ -15,6 +15,8 @@ int pinmux_check_ops(struct pinctrl_dev *pctldev);

int pinmux_validate_map(const struct pinctrl_map *map, int i);

+bool pinmux_can_be_used_for_gpio(struct pinctrl_dev *pctldev, unsigned pin);
+
int pinmux_request_gpio(struct pinctrl_dev *pctldev,
struct pinctrl_gpio_range *range,
unsigned pin, unsigned gpio);
@@ -42,6 +44,12 @@ static inline int pinmux_validate_map(const struct pinctrl_map *map, int i)
return 0;
}

+static inline bool pinmux_can_be_used_for_gpio(struct pinctrl_dev *pctldev,
+ unsigned pin)
+{
+ return true;
+}
+
static inline int pinmux_request_gpio(struct pinctrl_dev *pctldev,
struct pinctrl_gpio_range *range,
unsigned pin, unsigned gpio)
diff --git a/include/linux/pinctrl/consumer.h b/include/linux/pinctrl/consumer.h
index 86720a5a384f..7f8c7d9583d3 100644
--- a/include/linux/pinctrl/consumer.h
+++ b/include/linux/pinctrl/consumer.h
@@ -24,6 +24,7 @@ struct device;
#ifdef CONFIG_PINCTRL

/* External interface to pin control */
+extern bool pinctrl_gpio_can_use_line(unsigned gpio);
extern int pinctrl_gpio_request(unsigned gpio);
extern void pinctrl_gpio_free(unsigned gpio);
extern int pinctrl_gpio_direction_input(unsigned gpio);
@@ -61,6 +62,11 @@ static inline int pinctrl_pm_select_idle_state(struct device *dev)

#else /* !CONFIG_PINCTRL */

+static inline bool pinctrl_gpio_can_use_line(unsigned gpio)
+{
+ return true;
+}
+
static inline int pinctrl_gpio_request(unsigned gpio)
{
return 0;
--
2.20.1
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