[v3,4/5] gpiolib: add support for disabling line bias
diff mbox series

Message ID 20191020144238.14080-5-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 allows pull up/down bias to be disabled, allowing
the line to float or to be biased only by external circuitry.
Use case is for where the bias has been applied previously,
either by default or by the user, but that setting may
conflict with the current use of the line.

Signed-off-by: Kent Gibson <warthog618@gmail.com>
---
 drivers/gpio/gpiolib.c    | 63 ++++++++++++++++++++++++++++-----------
 drivers/gpio/gpiolib.h    |  1 +
 include/uapi/linux/gpio.h | 10 ++++---
 3 files changed, 53 insertions(+), 21 deletions(-)

Patch
diff mbox series

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index eef964417521..b6fdaedc793a 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -421,8 +421,9 @@  struct linehandle_state {
 	(GPIOHANDLE_REQUEST_INPUT | \
 	GPIOHANDLE_REQUEST_OUTPUT | \
 	GPIOHANDLE_REQUEST_ACTIVE_LOW | \
-	GPIOHANDLE_REQUEST_PULL_UP | \
-	GPIOHANDLE_REQUEST_PULL_DOWN | \
+	GPIOHANDLE_REQUEST_BIAS_DISABLE | \
+	GPIOHANDLE_REQUEST_BIAS_PULL_DOWN | \
+	GPIOHANDLE_REQUEST_BIAS_PULL_UP | \
 	GPIOHANDLE_REQUEST_OPEN_DRAIN | \
 	GPIOHANDLE_REQUEST_OPEN_SOURCE)
 
@@ -554,10 +555,11 @@  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. */
+	/* Bias flags only allowed for input mode. */
 	if (!(lflags & GPIOHANDLE_REQUEST_INPUT) &&
-	    ((lflags & GPIOHANDLE_REQUEST_PULL_UP) ||
-	     (lflags & GPIOHANDLE_REQUEST_PULL_DOWN)))
+	    ((lflags & GPIOHANDLE_REQUEST_BIAS_DISABLE) ||
+	     (lflags & GPIOHANDLE_REQUEST_BIAS_PULL_DOWN) ||
+	     (lflags & GPIOHANDLE_REQUEST_BIAS_PULL_UP)))
 		return -EINVAL;
 
 	lh = kzalloc(sizeof(*lh), GFP_KERNEL);
@@ -600,9 +602,11 @@  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)
+		if (lflags & GPIOHANDLE_REQUEST_BIAS_DISABLE)
+			set_bit(FLAG_BIAS_DISABLE, &desc->flags);
+		if (lflags & GPIOHANDLE_REQUEST_BIAS_PULL_DOWN)
 			set_bit(FLAG_PULL_DOWN, &desc->flags);
-		if (lflags & GPIOHANDLE_REQUEST_PULL_UP)
+		if (lflags & GPIOHANDLE_REQUEST_BIAS_PULL_UP)
 			set_bit(FLAG_PULL_UP, &desc->flags);
 
 		ret = gpiod_set_transitory(desc, false);
@@ -924,6 +928,13 @@  static int lineevent_create(struct gpio_device *gdev, void __user *ip)
 	    (lflags & GPIOHANDLE_REQUEST_OPEN_SOURCE))
 		return -EINVAL;
 
+	/* Bias flags only make sense for input mode. */
+	if (!(lflags & GPIOHANDLE_REQUEST_INPUT) &&
+	    ((lflags & GPIOHANDLE_REQUEST_BIAS_DISABLE) ||
+	     (lflags & GPIOHANDLE_REQUEST_BIAS_PULL_DOWN) ||
+	     (lflags & GPIOHANDLE_REQUEST_BIAS_PULL_UP)))
+		return -EINVAL;
+
 	le = kzalloc(sizeof(*le), GFP_KERNEL);
 	if (!le)
 		return -ENOMEM;
@@ -950,9 +961,11 @@  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)
+	if (lflags & GPIOHANDLE_REQUEST_BIAS_DISABLE)
+		set_bit(FLAG_BIAS_DISABLE, &desc->flags);
+	if (lflags & GPIOHANDLE_REQUEST_BIAS_PULL_DOWN)
 		set_bit(FLAG_PULL_DOWN, &desc->flags);
-	if (lflags & GPIOHANDLE_REQUEST_PULL_UP)
+	if (lflags & GPIOHANDLE_REQUEST_BIAS_PULL_UP)
 		set_bit(FLAG_PULL_UP, &desc->flags);
 
 	ret = gpiod_direction_input(desc);
@@ -1107,10 +1120,12 @@  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_BIAS_DISABLE, &desc->flags))
+			lineinfo.flags |= GPIOLINE_FLAG_BIAS_DISABLE;
 		if (test_bit(FLAG_PULL_DOWN, &desc->flags))
-			lineinfo.flags |= GPIOLINE_FLAG_PULL_DOWN;
+			lineinfo.flags |= GPIOLINE_FLAG_BIAS_PULL_DOWN;
 		if (test_bit(FLAG_PULL_UP, &desc->flags))
-			lineinfo.flags |= GPIOLINE_FLAG_PULL_UP;
+			lineinfo.flags |= GPIOLINE_FLAG_BIAS_PULL_UP;
 
 		if (copy_to_user(ip, &lineinfo, sizeof(lineinfo)))
 			return -EFAULT;
@@ -2786,6 +2801,7 @@  static bool gpiod_free_commit(struct gpio_desc *desc)
 		clear_bit(FLAG_OPEN_SOURCE, &desc->flags);
 		clear_bit(FLAG_PULL_UP, &desc->flags);
 		clear_bit(FLAG_PULL_DOWN, &desc->flags);
+		clear_bit(FLAG_BIAS_DISABLE, &desc->flags);
 		clear_bit(FLAG_IS_HOGGED, &desc->flags);
 		ret = true;
 	}
@@ -2912,6 +2928,7 @@  static int gpio_set_config(struct gpio_chip *gc, unsigned offset,
 	unsigned arg;
 
 	switch (mode) {
+	case PIN_CONFIG_BIAS_DISABLE:
 	case PIN_CONFIG_BIAS_PULL_DOWN:
 	case PIN_CONFIG_BIAS_PULL_UP:
 		arg = 1;
@@ -2925,6 +2942,23 @@  static int gpio_set_config(struct gpio_chip *gc, unsigned offset,
 	return gc->set_config ? gc->set_config(gc, offset, config) : -ENOTSUPP;
 }
 
+static int gpio_set_bias(struct gpio_chip *chip, struct gpio_desc *desc)
+{
+	int bias = 0;
+
+	if (test_bit(FLAG_BIAS_DISABLE, &desc->flags))
+		bias |= PIN_CONFIG_BIAS_DISABLE;
+	if (test_bit(FLAG_PULL_UP, &desc->flags))
+		bias |= PIN_CONFIG_BIAS_PULL_UP;
+	if (test_bit(FLAG_PULL_DOWN, &desc->flags))
+		bias |= PIN_CONFIG_BIAS_PULL_DOWN;
+
+	if (bias)
+		return gpio_set_config(chip, gpio_chip_hwgpio(desc), bias);
+
+	return 0;
+}
+
 /**
  * gpiod_direction_input - set the GPIO direction to input
  * @desc:	GPIO to set to input
@@ -2972,12 +3006,7 @@  int gpiod_direction_input(struct gpio_desc *desc)
 	if (ret == 0)
 		clear_bit(FLAG_IS_OUT, &desc->flags);
 
-	if (test_bit(FLAG_PULL_UP, &desc->flags))
-		gpio_set_config(chip, gpio_chip_hwgpio(desc),
-				PIN_CONFIG_BIAS_PULL_UP);
-	else if (test_bit(FLAG_PULL_DOWN, &desc->flags))
-		gpio_set_config(chip, gpio_chip_hwgpio(desc),
-				PIN_CONFIG_BIAS_PULL_DOWN);
+	gpio_set_bias(chip, desc);
 
 	trace_gpio_direction(desc_to_gpio(desc), 1, ret);
 
diff --git a/drivers/gpio/gpiolib.h b/drivers/gpio/gpiolib.h
index b8b10a409c7b..ca9bc1e4803c 100644
--- a/drivers/gpio/gpiolib.h
+++ b/drivers/gpio/gpiolib.h
@@ -110,6 +110,7 @@  struct gpio_desc {
 #define FLAG_TRANSITORY 12	/* GPIO may lose value in sleep or reset */
 #define FLAG_PULL_UP    13	/* GPIO has pull up enabled */
 #define FLAG_PULL_DOWN  14	/* GPIO has pull down enabled */
+#define FLAG_BIAS_DISABLE    15	/* GPIO has pull disabled */
 
 	/* Connection label */
 	const char		*label;
diff --git a/include/uapi/linux/gpio.h b/include/uapi/linux/gpio.h
index c2d1f7d908d6..300c2151e9f7 100644
--- a/include/uapi/linux/gpio.h
+++ b/include/uapi/linux/gpio.h
@@ -33,8 +33,9 @@  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)
+#define GPIOLINE_FLAG_BIAS_DISABLE	(1UL << 5)
+#define GPIOLINE_FLAG_BIAS_PULL_DOWN	(1UL << 6)
+#define GPIOLINE_FLAG_BIAS_PULL_UP	(1UL << 7)
 
 /**
  * struct gpioline_info - Information about a certain GPIO line
@@ -64,8 +65,9 @@  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)
+#define GPIOHANDLE_REQUEST_BIAS_DISABLE	(1UL << 5)
+#define GPIOHANDLE_REQUEST_BIAS_PULL_DOWN	(1UL << 6)
+#define GPIOHANDLE_REQUEST_BIAS_PULL_UP	(1UL << 7)
 
 /**
  * struct gpiohandle_request - Information about a GPIO handle request