[v3,2/5] gpiolib: add support for pull up/down to lineevent_create
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Message ID 20191020144238.14080-3-warthog618@gmail.com
State New
Headers show
Series
  • gpio: expose line bias flags to userspace
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Commit Message

Kent Gibson Oct. 20, 2019, 2:42 p.m. UTC
This patch adds support for pull up/down to lineevent_create.
Use cases include receiving asynchronous presses from a
push button without an external pull up/down.

The patch also restricts the application of bias to lines
explicitly requested as inputs to prevent bias being applied
to as-is line requests.

Signed-off-by: Kent Gibson <warthog618@gmail.com>
---
 drivers/gpio/gpiolib.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

Patch
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diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 604dc17b3207..eef964417521 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -554,6 +554,12 @@  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_PULL_UP) ||
+	     (lflags & GPIOHANDLE_REQUEST_PULL_DOWN)))
+		return -EINVAL;
+
 	lh = kzalloc(sizeof(*lh), GFP_KERNEL);
 	if (!lh)
 		return -ENOMEM;
@@ -944,6 +950,10 @@  static int lineevent_create(struct gpio_device *gdev, void __user *ip)
 
 	if (lflags & GPIOHANDLE_REQUEST_ACTIVE_LOW)
 		set_bit(FLAG_ACTIVE_LOW, &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_direction_input(desc);
 	if (ret)