diff options
| -rw-r--r-- | Documentation/gpio.txt | 15 | ||||
| -rw-r--r-- | drivers/gpio/gpiolib.c | 161 | ||||
| -rw-r--r-- | include/asm-generic/gpio.h | 6 | ||||
| -rw-r--r-- | include/linux/gpio.h | 6 |
4 files changed, 176 insertions, 12 deletions
diff --git a/Documentation/gpio.txt b/Documentation/gpio.txt index e4e7daed2ba8..1866c27eec69 100644 --- a/Documentation/gpio.txt +++ b/Documentation/gpio.txt @@ -531,6 +531,13 @@ and have the following read/write attributes: 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_export_link() allows creating 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 --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c index 50de0f5750d8..a25ad284a272 100644 --- a/drivers/gpio/gpiolib.c +++ b/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(struct device *dev, 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 device *dev, 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 device *dev, 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 device *dev, 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_desc *desc, struct device *dev, 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 direction_may_change) 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 --git a/include/asm-generic/gpio.h b/include/asm-generic/gpio.h index 204bed37e82d..485eeb6c4ef3 100644 --- a/include/asm-generic/gpio.h +++ b/include/asm-generic/gpio.h @@ -145,6 +145,7 @@ 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 */ @@ -197,6 +198,11 @@ static inline int gpio_export_link(struct device *dev, const char *name, return -ENOSYS; } +static inline int gpio_sysfs_set_active_low(unsigned gpio, int value) +{ + return -ENOSYS; +} + static inline void gpio_unexport(unsigned gpio) { } diff --git a/include/linux/gpio.h b/include/linux/gpio.h index 059bd189d35d..4e949a5b5b85 100644 --- a/include/linux/gpio.h +++ b/include/linux/gpio.h @@ -99,6 +99,12 @@ static inline int gpio_export_link(struct device *dev, const char *name, 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) { |