Skip to contentSkip to conversation

gpio: expose line bias flags to userspace

PATCH Superseded Kent Gibson 1 participant 6 messages Oct 20, 2019

Subsystems (3)
GPIO GPIO uapi GPIO mockup driver

v3 of 6 Superseded Latest is v6 →

lore
Share & tools
lore

Kent Gibson

author reviewer
#0 lore raw

v3 cover gpio: expose line bias flags to userspace

The major change from v2 is the change to three separate flags rather than encoding four possible values into a two bit field.

I expect more work is required. While I was initially satisfied with the patch, I have noticed a few deficiencies that I'm uncertain on how to best resolve:

There is no sanity checking on bias flag combinations, they are passed through unaltered to the pinctrl driver. I'd add sanity checks, but I'm unsure which combinations are invalid.

The setting of bias is performed by gpio_set_bias, which is hooked into gpiod_direction_input and gpiod_direction_output. It extends the setting of bias that was already present in gpiod_direction_input.
In keeping with the existing behaviour, the bias is set on a best-effort basis - no error is returned to the user if an error is returned by the pinctrl driver. Returning an error makes sense to me, particularly for the uAPI, but that conflicts with the existing gpiod_direction_input behaviour. So leave as best-effort, change gpiod_direction_input behaviour, or restructure to support both behaviours?

Also, the gpio_set_bias is hooked into gpiod_direction_output, which is fine for the uAPI, but perhaps it should be hooked into gpiod_direction_output_raw_commit? Or the setting of direction and bias should be decoupled?

And now the actual blurb...

This series adds gross control of pull-up/pull-down to the GPIO uAPI. Gross control means enabling and disabling of bias functionality, not finer grained control such as setting biasing impedances.

The support allows both input and output lines to have any one of the following biases applied as part of the line handle or event request:
0. As Is - bias is left alone. This is the default for ABI compatibility.
1. Bias Disable - bias is explicitly disabled.
2. Pull Down - pull-down bias is enabled.
3. Pull Up - pull-up bias is enabled.

The biases are set via three flags, BIAS_DISABLE, BIAS_PULL_DOWN and BIAS_PULL_UP. These map directly to the similarly named pinctrl pin_config_param flags.
As Is corresponds to none of the flags being set.

The setting of biases on output lines may seem odd, but is to allow for utilisation of internal pull-up/pull-down on open drain and open source outputs, where supported in hardware.

Patches are against Bart's gpio/for-next branch[1].

The patch has been successfully tested against gpio-mockup, and on a Raspberry Pi, in both cases using the feature/pud branch of my Go gpiod library[2], as libgpiod still requires updating to match.

Patch 1 adds support to line handle requests.
Patch 2 adds support to line event requests and restricts bias settings to lines explicitly requested as inputs.
Patch 3 adds pull-up/down support to the gpio-mockup for uAPI testing. Patch 4 adds support for disabling bias.
Patch 5 adds support for setting bias on output lines.

Drew Fustini (1):
gpio: expose pull-up/pull-down line flags to userspace

Kent Gibson (4):
gpiolib: add support for pull up/down to lineevent_create
gpio: mockup: add set_config to support pull up/down
gpiolib: add support for disabling line bias
gpiolib: add support for bias output lines

 drivers/gpio/gpio-mockup.c | 94 ++++++++++++++++++++++++--------------
 drivers/gpio/gpiolib.c     | 65 +++++++++++++++++++++++---
 drivers/gpio/gpiolib.h     |  1 +
 include/uapi/linux/gpio.h  |  6 +++
 4 files changed, 126 insertions(+), 40 deletions(-)
Signature · 4 lines
2.23.0

[1] git://git.kernel.org/pub/scm/linux/kernel/git/brgl/linux.git
[2] https://github.com/warthog618/gpiod.git
author reviewer
#1 lore raw

PATCH v3 1/5 gpio: expose pull-up/pull-down line flags to userspace

From: Drew Fustini <[email protected]>

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 <[email protected]>
---
 drivers/gpio/gpiolib.c    | 12 ++++++++++++
 include/uapi/linux/gpio.h |  4 ++++
 2 files changed, 16 insertions(+)
drivers/gpio/gpiolib.c +12 -0
index e8964493c571..604dc17b3207 100644
@@ -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)

@@ -1091,6 +1097,10 @@ 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;

@@ -2764,6 +2774,8 @@ 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 +4 -0
index 4ebfe0ac6c5b..c2d1f7d908d6 100644
@@ -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
Signature · 1 line
2.23.0
author reviewer
#2 lore raw

PATCH v3 2/5 gpiolib: add support for pull up/down to lineevent_create

In reply to Kent Gibson

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 <[email protected]>
---
 drivers/gpio/gpiolib.c | 10 ++++++++++
 1 file changed, 10 insertions(+)
drivers/gpio/gpiolib.c +10 -0
index 604dc17b3207..eef964417521 100644
@@ -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)
Signature · 1 line
2.23.0
author reviewer
#3 lore raw

PATCH v3 3/5 gpio: mockup: add set_config to support pull up/down

In reply to Kent Gibson

This patch adds support for the pull up/down state set via gpiolib line requests to be reflected in the state of the mockup.
Use case is for testing of the GPIO uAPI, specifically the pull up/down flags.

Signed-off-by Kent Gibson <[email protected]>
---
 drivers/gpio/gpio-mockup.c | 94 ++++++++++++++++++++++++--------------
 1 file changed, 60 insertions(+), 34 deletions(-)
drivers/gpio/gpio-mockup.c +60 -34
index 213aedc97dc2..c28219962ae2 100644
@@ -146,6 +146,61 @@ static void gpio_mockup_set_multiple(struct gpio_chip *gc,
 	mutex_unlock(&chip->lock);
 }
 
+static int gpio_mockup_apply_pull(struct gpio_mockup_chip *chip,
+				  unsigned int offset, int value)
+{
+	struct gpio_desc *desc;
+	struct gpio_chip *gc;
+	struct irq_sim *sim;
+	int curr, irq, irq_type;
+
+	gc = &chip->gc;
+	desc = &gc->gpiodev->descs[offset];
+	sim = &chip->irqsim;
+
+	mutex_lock(&chip->lock);
+
+	if (test_bit(FLAG_REQUESTED, &desc->flags) &&
+		!test_bit(FLAG_IS_OUT, &desc->flags)) {
+		curr = __gpio_mockup_get(chip, offset);
+		if (curr == value)
+			goto out;
+
+		irq = irq_sim_irqnum(sim, offset);
+		irq_type = irq_get_trigger_type(irq);
+
+		if ((value == 1 && (irq_type & IRQ_TYPE_EDGE_RISING)) ||
+			(value == 0 && (irq_type & IRQ_TYPE_EDGE_FALLING)))
+			irq_sim_fire(sim, offset);
+	}
+
+	/* Change the value unless we're actively driving the line. */
+	if (!test_bit(FLAG_REQUESTED, &desc->flags) ||
+		!test_bit(FLAG_IS_OUT, &desc->flags))
+		__gpio_mockup_set(chip, offset, value);
+
+out:
+	chip->lines[offset].pull = value;
+	mutex_unlock(&chip->lock);
+	return 0;
+}
+
+static int gpio_mockup_set_config(struct gpio_chip *gc,
+				  unsigned int offset, unsigned long config)
+{
+	struct gpio_mockup_chip *chip = gpiochip_get_data(gc);
+
+	switch (pinconf_to_config_param(config)) {
+	case PIN_CONFIG_BIAS_PULL_UP:
+		return gpio_mockup_apply_pull(chip, offset, 1);
+	case PIN_CONFIG_BIAS_PULL_DOWN:
+		return gpio_mockup_apply_pull(chip, offset, 0);
+	default:
+		break;
+	}
+	return -ENOTSUPP;
+}
+
 static int gpio_mockup_dirout(struct gpio_chip *gc,
 			      unsigned int offset, int value)
 {

@@ -226,12 +281,8 @@ static ssize_t gpio_mockup_debugfs_write(struct file *file,
 					 size_t size, loff_t *ppos)
 {
 	struct gpio_mockup_dbgfs_private *priv;
-	int rv, val, curr, irq, irq_type;
-	struct gpio_mockup_chip *chip;
+	int rv, val;
 	struct seq_file *sfile;
-	struct gpio_desc *desc;
-	struct gpio_chip *gc;
-	struct irq_sim *sim;
 
 	if (*ppos != 0)
 		return -EINVAL;

@@ -244,35 +295,9 @@ static ssize_t gpio_mockup_debugfs_write(struct file *file,
 
 	sfile = file->private_data;
 	priv = sfile->private;
-	chip = priv->chip;
-	gc = &chip->gc;
-	desc = &gc->gpiodev->descs[priv->offset];
-	sim = &chip->irqsim;
-
-	mutex_lock(&chip->lock);
-
-	if (test_bit(FLAG_REQUESTED, &desc->flags) &&
-	    !test_bit(FLAG_IS_OUT, &desc->flags)) {
-		curr = __gpio_mockup_get(chip, priv->offset);
-		if (curr == val)
-			goto out;
-
-		irq = irq_sim_irqnum(sim, priv->offset);
-		irq_type = irq_get_trigger_type(irq);
-
-		if ((val == 1 && (irq_type & IRQ_TYPE_EDGE_RISING)) ||
-		    (val == 0 && (irq_type & IRQ_TYPE_EDGE_FALLING)))
-			irq_sim_fire(sim, priv->offset);
-	}
-
-	/* Change the value unless we're actively driving the line. */
-	if (!test_bit(FLAG_REQUESTED, &desc->flags) ||
-	    !test_bit(FLAG_IS_OUT, &desc->flags))
-		__gpio_mockup_set(chip, priv->offset, val);
-
-out:
-	chip->lines[priv->offset].pull = val;
-	mutex_unlock(&chip->lock);
+	rv = gpio_mockup_apply_pull(priv->chip, priv->offset, val);
+	if (rv)
+		return rv;
 
 	return size;
 }

@@ -418,6 +443,7 @@ static int gpio_mockup_probe(struct platform_device *pdev)
 	gc->direction_output = gpio_mockup_dirout;
 	gc->direction_input = gpio_mockup_dirin;
 	gc->get_direction = gpio_mockup_get_direction;
+	gc->set_config = gpio_mockup_set_config;
 	gc->to_irq = gpio_mockup_to_irq;
 	gc->free = gpio_mockup_free;
Signature · 1 line
2.23.0
author reviewer
#4 lore raw

PATCH v3 4/5 gpiolib: add support for disabling line bias

In reply to Kent Gibson

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 <[email protected]>
---
 drivers/gpio/gpiolib.c    | 63 ++++++++++++++++++++++++++++-----------
 drivers/gpio/gpiolib.h    |  1 +
 include/uapi/linux/gpio.h | 10 ++++---
 3 files changed, 53 insertions(+), 21 deletions(-)
drivers/gpio/gpiolib.c +46 -17
index eef964417521..b6fdaedc793a 100644
@@ -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);
drivers/gpio/gpiolib.h +1 -0
index b8b10a409c7b..ca9bc1e4803c 100644
@@ -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;
include/uapi/linux/gpio.h +6 -4
index c2d1f7d908d6..300c2151e9f7 100644
@@ -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
Signature · 1 line
2.23.0
author reviewer
#5 lore raw

PATCH v3 5/5 gpiolib: add support for biasing output lines

In reply to Kent Gibson

This patch allows pull up/down bias to be set on outputs. Use case is for open source or open drain applications where internal pull up/down may conflict with external biasing.

Signed-off-by Kent Gibson <[email protected]>
---
 drivers/gpio/gpiolib.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)
drivers/gpio/gpiolib.c +4 -2
index b6fdaedc793a..f1f6a390e7f5 100644
@@ -555,8 +555,9 @@ static int linehandle_create(struct gpio_device *gdev, void __user *ip)
 	     (lflags & GPIOHANDLE_REQUEST_OPEN_SOURCE)))
 		return -EINVAL;
 
-	/* Bias flags only allowed for input mode. */
-	if (!(lflags & GPIOHANDLE_REQUEST_INPUT) &&
+	/* Bias flags only allowed for input or output mode. */
+	if (!((lflags & GPIOHANDLE_REQUEST_INPUT) ||
+	      (lflags & GPIOHANDLE_REQUEST_OUTPUT)) &&
 	    ((lflags & GPIOHANDLE_REQUEST_BIAS_DISABLE) ||
 	     (lflags & GPIOHANDLE_REQUEST_BIAS_PULL_DOWN) ||
 	     (lflags & GPIOHANDLE_REQUEST_BIAS_PULL_UP)))

@@ -3132,6 +3133,7 @@ int gpiod_direction_output(struct gpio_desc *desc, int value)
 	}
 
 set_output_value:
+	gpio_set_bias(gc, desc);
 	return gpiod_direction_output_raw_commit(desc, value);
 }
 EXPORT_SYMBOL_GPL(gpiod_direction_output);
Signature · 1 line
2.23.0