The patch titled
gpiolib: add support for changing value polarity in sysfs
has been added to the -mm tree. Its filename is
gpiolib-add-support-for-changing-value-polarity-in-the-sysfs.patch
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Subject: gpiolib: add support for changing value polarity in sysfs
From: Jani Nikula <ext-jani.1.nikula@xxxxxxxxx>
Drivers may use gpiolib sysfs as part of their public user space
interface. The GPIO number and polarity might change from board to
board. The gpio_export_link() call can be used to hide the GPIO number
from user space. Add support for also hiding the GPIO line polarity
changes from user space.
Signed-off-by: Jani Nikula <ext-jani.1.nikula@xxxxxxxxx>
Cc: David Brownell <david-b@xxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
diff -puN Documentation/gpio.txt~gpiolib-add-support-for-changing-value-polarity-in-the-sysfs Documentation/gpio.txt
--- a/Documentation/gpio.txt~gpiolib-add-support-for-changing-value-polarity-in-the-sysfs
+++ a/Documentation/gpio.txt
@@ -531,6 +531,13 @@ and have the following read/write attrib
This file exists only if the pin can be configured as an
interrupt generating input pin.
+ "active_low" ... reads as either 0 (false) or 1 (true). Write
+ any nonzero value to invert the value attribute both
+ for reading and writing. Existing and subsequent
+ poll(2) support configuration via the edge attribute
+ for "rising" and "falling" edges will follow this
+ setting.
+
GPIO controllers have paths like /sys/class/gpio/gpiochip42/ (for the
controller implementing GPIOs starting at #42) and have the following
read-only attributes:
@@ -566,6 +573,8 @@ requested using gpio_request():
int gpio_export_link(struct device *dev, const char *name,
unsigned gpio)
+ /* change the polarity of a GPIO node in sysfs */
+ int gpio_sysfs_set_active_low(unsigned gpio, int value);
After a kernel driver requests a GPIO, it may only be made available in
the sysfs interface by gpio_export(). The driver can control whether the
@@ -580,3 +589,9 @@ After the GPIO has been exported, gpio_e
symlinks from elsewhere in sysfs to the GPIO sysfs node. Drivers can
use this to provide the interface under their own device in sysfs with
a descriptive name.
+
+Drivers can use gpio_sysfs_set_active_low() to hide GPIO line polarity
+differences between boards from user space. This only affects the
+sysfs interface. Polarity change can be done both before and after
+gpio_export(), and previously enabled poll(2) support for either
+rising or falling edge will be reconfigured to follow this setting.
diff -puN drivers/gpio/gpiolib.c~gpiolib-add-support-for-changing-value-polarity-in-the-sysfs drivers/gpio/gpiolib.c
--- a/drivers/gpio/gpiolib.c~gpiolib-add-support-for-changing-value-polarity-in-the-sysfs
+++ a/drivers/gpio/gpiolib.c
@@ -53,6 +53,7 @@ struct gpio_desc {
#define FLAG_SYSFS 4 /* exported via /sys/class/gpio/control */
#define FLAG_TRIG_FALL 5 /* trigger on falling edge */
#define FLAG_TRIG_RISE 6 /* trigger on rising edge */
+#define FLAG_ACTIVE_LOW 7 /* sysfs value has active low */
#define PDESC_ID_SHIFT 16 /* add new flags before this one */
@@ -210,6 +211,11 @@ static DEFINE_MUTEX(sysfs_lock);
* * configures behavior of poll(2) on /value
* * available only if pin can generate IRQs on input
* * is read/write as "none", "falling", "rising", or "both"
+ * /active_low
+ * * configures polarity of /value
+ * * is read/write as zero/nonzero
+ * * also affects existing and subsequent "falling" and "rising"
+ * /edge configuration
*/
static ssize_t gpio_direction_show(struct device *dev,
@@ -255,7 +261,7 @@ static ssize_t gpio_direction_store(stru
return status ? : size;
}
-static const DEVICE_ATTR(direction, 0644,
+static /* const */ DEVICE_ATTR(direction, 0644,
gpio_direction_show, gpio_direction_store);
static ssize_t gpio_value_show(struct device *dev,
@@ -267,10 +273,17 @@ static ssize_t gpio_value_show(struct de
mutex_lock(&sysfs_lock);
- if (!test_bit(FLAG_EXPORT, &desc->flags))
+ if (!test_bit(FLAG_EXPORT, &desc->flags)) {
status = -EIO;
- else
- status = sprintf(buf, "%d\n", !!gpio_get_value_cansleep(gpio));
+ } else {
+ int value;
+
+ value = !!gpio_get_value_cansleep(gpio);
+ if (test_bit(FLAG_ACTIVE_LOW, &desc->flags))
+ value = !value;
+
+ status = sprintf(buf, "%d\n", value);
+ }
mutex_unlock(&sysfs_lock);
return status;
@@ -294,6 +307,8 @@ static ssize_t gpio_value_store(struct d
status = strict_strtol(buf, 0, &value);
if (status == 0) {
+ if (test_bit(FLAG_ACTIVE_LOW, &desc->flags))
+ value = !value;
gpio_set_value_cansleep(gpio, value != 0);
status = size;
}
@@ -303,7 +318,7 @@ static ssize_t gpio_value_store(struct d
return status;
}
-static /*const*/ DEVICE_ATTR(value, 0644,
+static const DEVICE_ATTR(value, 0644,
gpio_value_show, gpio_value_store);
static irqreturn_t gpio_sysfs_irq(int irq, void *priv)
@@ -352,9 +367,11 @@ static int gpio_setup_irq(struct gpio_de
irq_flags = IRQF_SHARED;
if (test_bit(FLAG_TRIG_FALL, &gpio_flags))
- irq_flags |= IRQF_TRIGGER_FALLING;
+ irq_flags |= test_bit(FLAG_ACTIVE_LOW, &desc->flags) ?
+ IRQF_TRIGGER_RISING : IRQF_TRIGGER_FALLING;
if (test_bit(FLAG_TRIG_RISE, &gpio_flags))
- irq_flags |= IRQF_TRIGGER_RISING;
+ irq_flags |= test_bit(FLAG_ACTIVE_LOW, &desc->flags) ?
+ IRQF_TRIGGER_FALLING : IRQF_TRIGGER_RISING;
if (!pdesc) {
pdesc = kmalloc(sizeof(*pdesc), GFP_KERNEL);
@@ -475,9 +492,79 @@ found:
static DEVICE_ATTR(edge, 0644, gpio_edge_show, gpio_edge_store);
+static int sysfs_set_active_low(struct gpio_desc *desc, struct device *dev,
+ int value)
+{
+ int status = 0;
+
+ if (!!test_bit(FLAG_ACTIVE_LOW, &desc->flags) == !!value)
+ return 0;
+
+ if (value)
+ set_bit(FLAG_ACTIVE_LOW, &desc->flags);
+ else
+ clear_bit(FLAG_ACTIVE_LOW, &desc->flags);
+
+ /* reconfigure poll(2) support if enabled on one edge only */
+ if (dev != NULL && (!!test_bit(FLAG_TRIG_RISE, &desc->flags) ^
+ !!test_bit(FLAG_TRIG_FALL, &desc->flags))) {
+ unsigned long trigger_flags = desc->flags & GPIO_TRIGGER_MASK;
+
+ gpio_setup_irq(desc, dev, 0);
+ status = gpio_setup_irq(desc, dev, trigger_flags);
+ }
+
+ return status;
+}
+
+static ssize_t gpio_active_low_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ const struct gpio_desc *desc = dev_get_drvdata(dev);
+ ssize_t status;
+
+ mutex_lock(&sysfs_lock);
+
+ if (!test_bit(FLAG_EXPORT, &desc->flags))
+ status = -EIO;
+ else
+ status = sprintf(buf, "%d\n",
+ !!test_bit(FLAG_ACTIVE_LOW, &desc->flags));
+
+ mutex_unlock(&sysfs_lock);
+
+ return status;
+}
+
+static ssize_t gpio_active_low_store(struct device *dev,
+ struct device_attribute *attr, const char *buf, size_t size)
+{
+ struct gpio_desc *desc = dev_get_drvdata(dev);
+ ssize_t status;
+
+ mutex_lock(&sysfs_lock);
+
+ if (!test_bit(FLAG_EXPORT, &desc->flags)) {
+ status = -EIO;
+ } else {
+ long value;
+
+ status = strict_strtol(buf, 0, &value);
+ if (status == 0)
+ status = sysfs_set_active_low(desc, dev, value != 0);
+ }
+
+ mutex_unlock(&sysfs_lock);
+
+ return status ? : size;
+}
+
+static const DEVICE_ATTR(active_low, 0644,
+ gpio_active_low_show, gpio_active_low_store);
+
static const struct attribute *gpio_attrs[] = {
- &dev_attr_direction.attr,
&dev_attr_value.attr,
+ &dev_attr_active_low.attr,
NULL,
};
@@ -662,12 +749,12 @@ int gpio_export(unsigned gpio, bool dire
dev = device_create(&gpio_class, desc->chip->dev, MKDEV(0, 0),
desc, ioname ? ioname : "gpio%d", gpio);
if (!IS_ERR(dev)) {
- if (direction_may_change)
- status = sysfs_create_group(&dev->kobj,
+ status = sysfs_create_group(&dev->kobj,
&gpio_attr_group);
- else
+
+ if (!status && direction_may_change)
status = device_create_file(dev,
- &dev_attr_value);
+ &dev_attr_direction);
if (!status && gpio_to_irq(gpio) >= 0
&& (direction_may_change
@@ -744,6 +831,55 @@ done:
}
EXPORT_SYMBOL_GPL(gpio_export_link);
+
+/**
+ * gpio_sysfs_set_active_low - set the polarity of gpio sysfs value
+ * @gpio: gpio to change
+ * @value: non-zero to use active low, i.e. inverted values
+ *
+ * Set the polarity of /sys/class/gpio/gpioN/value sysfs attribute.
+ * The GPIO does not have to be exported yet. If poll(2) support has
+ * been enabled for either rising or falling edge, it will be
+ * reconfigured to follow the new polarity.
+ *
+ * Returns zero on success, else an error.
+ */
+int gpio_sysfs_set_active_low(unsigned gpio, int value)
+{
+ struct gpio_desc *desc;
+ struct device *dev = NULL;
+ int status = -EINVAL;
+
+ if (!gpio_is_valid(gpio))
+ goto done;
+
+ mutex_lock(&sysfs_lock);
+
+ desc = &gpio_desc[gpio];
+
+ if (test_bit(FLAG_EXPORT, &desc->flags)) {
+ struct device *dev;
+
+ dev = class_find_device(&gpio_class, NULL, desc, match_export);
+ if (dev == NULL) {
+ status = -ENODEV;
+ goto unlock;
+ }
+ }
+
+ status = sysfs_set_active_low(desc, dev, value);
+
+unlock:
+ mutex_unlock(&sysfs_lock);
+
+done:
+ if (status)
+ pr_debug("%s: gpio%d status %d\n", __func__, gpio, status);
+
+ return status;
+}
+EXPORT_SYMBOL_GPL(gpio_sysfs_set_active_low);
+
/**
* gpio_unexport - reverse effect of gpio_export()
* @gpio: gpio to make unavailable
@@ -1094,6 +1230,7 @@ void gpio_free(unsigned gpio)
}
desc_set_label(desc, NULL);
module_put(desc->chip->owner);
+ clear_bit(FLAG_ACTIVE_LOW, &desc->flags);
clear_bit(FLAG_REQUESTED, &desc->flags);
} else
WARN_ON(extra_checks);
diff -puN include/asm-generic/gpio.h~gpiolib-add-support-for-changing-value-polarity-in-the-sysfs include/asm-generic/gpio.h
--- a/include/asm-generic/gpio.h~gpiolib-add-support-for-changing-value-polarity-in-the-sysfs
+++ a/include/asm-generic/gpio.h
@@ -144,6 +144,7 @@ extern int __gpio_to_irq(unsigned gpio);
extern int gpio_export(unsigned gpio, bool direction_may_change);
extern int gpio_export_link(struct device *dev, const char *name,
unsigned gpio);
+extern int gpio_sysfs_set_active_low(unsigned gpio, int value);
extern void gpio_unexport(unsigned gpio);
#endif /* CONFIG_GPIO_SYSFS */
@@ -194,6 +195,11 @@ static inline int gpio_export_link(struc
return -ENOSYS;
}
+static inline int gpio_sysfs_set_active_low(unsigned gpio, int value)
+{
+ return -ENOSYS;
+}
+
static inline void gpio_unexport(unsigned gpio)
{
}
diff -puN include/linux/gpio.h~gpiolib-add-support-for-changing-value-polarity-in-the-sysfs include/linux/gpio.h
--- a/include/linux/gpio.h~gpiolib-add-support-for-changing-value-polarity-in-the-sysfs
+++ a/include/linux/gpio.h
@@ -99,6 +99,12 @@ static inline int gpio_export_link(struc
return -EINVAL;
}
+static inline int gpio_sysfs_set_active_low(unsigned gpio, int value)
+{
+ /* GPIO can never have been requested */
+ WARN_ON(1);
+ return -EINVAL;
+}
static inline void gpio_unexport(unsigned gpio)
{
_
Patches currently in -mm which might be from ext-jani.1.nikula@xxxxxxxxx are
gpiolib-add-support-for-changing-value-polarity-in-the-sysfs.patch
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