pinctrl/gpio: Take MUX usage into account

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>
Link: https://lore.kernel.org/r/20190814110035.13451-1-ramon.fried@linux.intel.com
Acked-by: Stefan Wahren <stefan.wahren@i2se.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

1 files changed, 24 insertions, 0 deletions

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
@@ -71,6 +71,30 @@ int pinmux_validate_map(const struct pinctrl_map *map, int i)
 }
 
 /**
+ * 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
  * @owner: a representation of the owner of this pin; typically the device