gpio: expose pull-up/pull-down line flags to userspace

Add pull-up/pull-down flags to the gpio line get and
set ioctl() calls.  Use cases include a push button
that does not have an external resistor.

Addition use cases described by Limor Fried (ladyada) of
Adafruit in this PR for Adafruit_Blinka Python lib:
https://github.com/adafruit/Adafruit_Blinka/pull/59

Signed-off-by: Drew Fustini <drew@pdp7.com>
[Kent: added BIAS to GPIO flag names and restrict application to input
lines]
Signed-off-by: Kent Gibson <warthog618@gmail.com>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 731d732..5308672 100644 (file)
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -422,6 +422,8 @@ struct linehandle_state {
        (GPIOHANDLE_REQUEST_INPUT | \
        GPIOHANDLE_REQUEST_OUTPUT | \
        GPIOHANDLE_REQUEST_ACTIVE_LOW | \
+       GPIOHANDLE_REQUEST_BIAS_PULL_UP | \
+       GPIOHANDLE_REQUEST_BIAS_PULL_DOWN | \
        GPIOHANDLE_REQUEST_OPEN_DRAIN | \
        GPIOHANDLE_REQUEST_OPEN_SOURCE)
 
@@ -553,6 +555,12 @@ static int linehandle_create(struct gpio_device *gdev, void __user *ip)
             (lflags & GPIOHANDLE_REQUEST_OPEN_SOURCE)))
                return -EINVAL;
 
+       /* PULL_UP and PULL_DOWN flags only make sense for input mode. */
+       if (!(lflags & GPIOHANDLE_REQUEST_INPUT) &&
+           ((lflags & GPIOHANDLE_REQUEST_BIAS_PULL_UP) ||
+            (lflags & GPIOHANDLE_REQUEST_BIAS_PULL_DOWN)))
+               return -EINVAL;
+
        lh = kzalloc(sizeof(*lh), GFP_KERNEL);
        if (!lh)
                return -ENOMEM;
@@ -593,6 +601,10 @@ static int linehandle_create(struct gpio_device *gdev, void __user *ip)
                        set_bit(FLAG_OPEN_DRAIN, &desc->flags);
                if (lflags & GPIOHANDLE_REQUEST_OPEN_SOURCE)
                        set_bit(FLAG_OPEN_SOURCE, &desc->flags);
+               if (lflags & GPIOHANDLE_REQUEST_BIAS_PULL_DOWN)
+                       set_bit(FLAG_PULL_DOWN, &desc->flags);
+               if (lflags & GPIOHANDLE_REQUEST_BIAS_PULL_UP)
+                       set_bit(FLAG_PULL_UP, &desc->flags);
 
                ret = gpiod_set_transitory(desc, false);
                if (ret < 0)
@@ -1092,6 +1104,10 @@ static long gpio_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
                if (test_bit(FLAG_OPEN_SOURCE, &desc->flags))
                        lineinfo.flags |= (GPIOLINE_FLAG_OPEN_SOURCE |
                                           GPIOLINE_FLAG_IS_OUT);
+               if (test_bit(FLAG_PULL_DOWN, &desc->flags))
+                       lineinfo.flags |= GPIOLINE_FLAG_BIAS_PULL_DOWN;
+               if (test_bit(FLAG_PULL_UP, &desc->flags))
+                       lineinfo.flags |= GPIOLINE_FLAG_BIAS_PULL_UP;
 
                if (copy_to_user(ip, &lineinfo, sizeof(lineinfo)))
                        return -EFAULT;
@@ -2785,6 +2801,8 @@ static bool gpiod_free_commit(struct gpio_desc *desc)
                clear_bit(FLAG_REQUESTED, &desc->flags);
                clear_bit(FLAG_OPEN_DRAIN, &desc->flags);
                clear_bit(FLAG_OPEN_SOURCE, &desc->flags);
+               clear_bit(FLAG_PULL_UP, &desc->flags);
+               clear_bit(FLAG_PULL_DOWN, &desc->flags);
                clear_bit(FLAG_IS_HOGGED, &desc->flags);
                ret = true;
        }

diff --git a/include/uapi/linux/gpio.h b/include/uapi/linux/gpio.h
index 4ebfe0a..39e6c78 100644 (file)
--- a/include/uapi/linux/gpio.h
+++ b/include/uapi/linux/gpio.h
@@ -33,6 +33,8 @@ struct gpiochip_info {
 #define GPIOLINE_FLAG_ACTIVE_LOW       (1UL << 2)
 #define GPIOLINE_FLAG_OPEN_DRAIN       (1UL << 3)
 #define GPIOLINE_FLAG_OPEN_SOURCE      (1UL << 4)
+#define GPIOLINE_FLAG_BIAS_PULL_UP     (1UL << 5)
+#define GPIOLINE_FLAG_BIAS_PULL_DOWN   (1UL << 6)
 
 /**
  * struct gpioline_info - Information about a certain GPIO line
@@ -62,6 +64,8 @@ struct gpioline_info {
 #define GPIOHANDLE_REQUEST_ACTIVE_LOW  (1UL << 2)
 #define GPIOHANDLE_REQUEST_OPEN_DRAIN  (1UL << 3)
 #define GPIOHANDLE_REQUEST_OPEN_SOURCE (1UL << 4)
+#define GPIOHANDLE_REQUEST_BIAS_PULL_UP        (1UL << 5)
+#define GPIOHANDLE_REQUEST_BIAS_PULL_DOWN      (1UL << 6)
 
 /**
  * struct gpiohandle_request - Information about a GPIO handle request