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/59Signed-off-by: Drew Fustini <drew@pdp7.com>
Link: https://lore.kernel.org/r/20190921102522.8970-1-drew@pdp7.comSigned-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/gpiolib.c

@@ -421,6 +421,8 @@ struct linehandle_state {
 	(GPIOHANDLE_REQUEST_INPUT | \
 	GPIOHANDLE_REQUEST_OUTPUT | \
 	GPIOHANDLE_REQUEST_ACTIVE_LOW | \
+	GPIOHANDLE_REQUEST_PULL_UP | \
+	GPIOHANDLE_REQUEST_PULL_DOWN | \
 	GPIOHANDLE_REQUEST_OPEN_DRAIN | \
 	GPIOHANDLE_REQUEST_OPEN_SOURCE)
 
@@ -592,6 +594,10 @@ 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_PULL_DOWN)
+			set_bit(FLAG_PULL_DOWN, &desc->flags);
+		if (lflags & GPIOHANDLE_REQUEST_PULL_UP)
+			set_bit(FLAG_PULL_UP, &desc->flags);
 
 		ret = gpiod_set_transitory(desc, false);
 		if (ret < 0)
@@ -1097,6 +1103,10 @@ 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_PULL_DOWN;
+		if (test_bit(FLAG_PULL_UP, &desc->flags))
+			lineinfo.flags |= GPIOLINE_FLAG_PULL_UP;
 
 		if (copy_to_user(ip, &lineinfo, sizeof(lineinfo)))
 			return -EFAULT;
@@ -2770,6 +2780,8 @@ 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;
 	}

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_PULL_UP	(1UL << 5)
+#define GPIOLINE_FLAG_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_PULL_UP	(1UL << 5)
+#define GPIOHANDLE_REQUEST_PULL_DOWN	(1UL << 6)
 
 /**
  * struct gpiohandle_request - Information about a GPIO handle request