gpio: remove gpiod_sysfs_set_active_low

Remove gpiod_sysfs_set_active_low (and gpio_sysfs_set_active_low) which
allowed code to change the polarity of a gpio line even after it had
been exported through sysfs.

Drivers should not care, and generally does not know, about gpio-line
polarity which is a hardware feature that needs to be described by
firmware.

It is currently possible to define gpio-line polarity in device-tree and
acpi firmware or using platform data. Userspace can also change the
polarity through sysfs.

Note that drivers using the legacy gpio interface could still use
GPIOF_ACTIVE_LOW to change the polarity before exporting the gpio.

There are no in-kernel users of this interface.

Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Harry Wei <harryxiyou@gmail.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: linux-doc@vger.kernel.org
Cc: linux-kernel@zh-kernel.org
Cc: linux-arch@vger.kernel.org
Signed-off-by: Johan Hovold <johan@kernel.org>
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

Documentation/gpio/gpio-legacy.txt

@@ -751,9 +751,6 @@ 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
 signal direction may change.  This helps drivers prevent userspace code
@@ -767,9 +764,3 @@ 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.

Documentation/gpio/sysfs.txt

@@ -132,9 +132,6 @@ requested using gpio_request():
 	int gpiod_export_link(struct device *dev, const char *name,
 		      struct gpio_desc *desc);
 
-	/* change the polarity of a GPIO node in sysfs */
-	int gpiod_sysfs_set_active_low(struct gpio_desc *desc, int value);
-
 After a kernel driver requests a GPIO, it may only be made available in
 the sysfs interface by gpiod_export(). The driver can control whether the
 signal direction may change. This helps drivers prevent userspace code
@@ -148,8 +145,3 @@ After the GPIO has been exported, gpiod_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 gpiod_sysfs_set_active_low() to hide GPIO line polarity
-differences between boards from user space. Polarity change can be done both
-before and after gpiod_export(), and previously enabled poll(2) support for
-either rising or falling edge will be reconfigured to follow this setting.

Documentation/zh_CN/gpio.txt

@@ -638,9 +638,6 @@ GPIO 控制器的路径类似 /sys/class/gpio/gpiochip42/ (对于从#42 GPIO
 	int gpio_export_link(struct device *dev, const char *name,
 		unsigned gpio)
 
-	/* 改变 sysfs 中的一个 GPIO 节点的极性 */
-	int gpio_sysfs_set_active_low(unsigned gpio, int value);
-
 在一个内核驱动申请一个 GPIO 之后，它可以通过 gpio_export()使其在 sysfs
 接口中可见。该驱动可以控制信号方向是否可修改。这有助于防止用户空间代码无意间
 破坏重要的系统状态。
@@ -651,8 +648,3 @@ GPIO 控制器的路径类似 /sys/class/gpio/gpiochip42/ (对于从#42 GPIO
 在 GPIO 被导出之后，gpio_export_link()允许在 sysfs 文件系统的任何地方
 创建一个到这个 GPIO sysfs 节点的符号链接。这样驱动就可以通过一个描述性的
 名字，在 sysfs 中他们所拥有的设备下提供一个(到这个 GPIO sysfs 节点的)接口。
-
-驱动可以使用 gpio_sysfs_set_active_low() 来在用户空间隐藏电路板之间
-GPIO 线的极性差异。这个仅对 sysfs 接口起作用。极性的改变可以在 gpio_export()
-前后进行,且之前使能的轮询操作(poll(2))支持(上升或下降沿)将会被重新配置来遵循
-这个设置。

drivers/gpio/gpiolib-sysfs.c

@@ -308,8 +308,8 @@ static int sysfs_set_active_low(struct gpio_desc *desc, struct device *dev,
 		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) ^
+	if (!!test_bit(FLAG_TRIG_RISE, &desc->flags) ^
-				!!test_bit(FLAG_TRIG_FALL, &desc->flags))) {
+				!!test_bit(FLAG_TRIG_FALL, &desc->flags)) {
 		unsigned long trigger_flags = desc->flags & GPIO_TRIGGER_MASK;
 
 		gpio_setup_irq(desc, dev, 0);
@@ -680,50 +680,6 @@ int gpiod_export_link(struct device *dev, const char *name,
 }
 EXPORT_SYMBOL_GPL(gpiod_export_link);
 
-/**
- * gpiod_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 gpiod_sysfs_set_active_low(struct gpio_desc *desc, int value)
-{
-	struct device		*dev = NULL;
-	int			status = -EINVAL;
-
-	if (!desc) {
-		pr_warn("%s: invalid GPIO\n", __func__);
-		return -EINVAL;
-	}
-
-	mutex_lock(&sysfs_lock);
-
-	if (test_bit(FLAG_EXPORT, &desc->flags)) {
-		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);
-	put_device(dev);
-unlock:
-	mutex_unlock(&sysfs_lock);
-
-	if (status)
-		gpiod_dbg(desc, "%s: status %d\n", __func__, status);
-
-	return status;
-}
-EXPORT_SYMBOL_GPL(gpiod_sysfs_set_active_low);
-
 /**
  * gpiod_unexport - reverse effect of gpio_export()
  * @gpio: gpio to make unavailable

include/asm-generic/gpio.h

@@ -128,11 +128,6 @@ static inline int gpio_export_link(struct device *dev, const char *name,
 	return gpiod_export_link(dev, name, gpio_to_desc(gpio));
 }
 
-static inline int gpio_sysfs_set_active_low(unsigned gpio, int value)
-{
-	return gpiod_sysfs_set_active_low(gpio_to_desc(gpio), value);
-}
-
 static inline void gpio_unexport(unsigned gpio)
 {
 	gpiod_unexport(gpio_to_desc(gpio));

include/linux/gpio.h

@@ -196,13 +196,6 @@ 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)
 {
 	/* GPIO can never have been exported */

include/linux/gpio/consumer.h

@@ -449,7 +449,6 @@ static inline int desc_to_gpio(const struct gpio_desc *desc)
 int gpiod_export(struct gpio_desc *desc, bool direction_may_change);
 int gpiod_export_link(struct device *dev, const char *name,
 		      struct gpio_desc *desc);
-int gpiod_sysfs_set_active_low(struct gpio_desc *desc, int value);
 void gpiod_unexport(struct gpio_desc *desc);
 
 #else  /* CONFIG_GPIOLIB && CONFIG_GPIO_SYSFS */
@@ -466,11 +465,6 @@ static inline int gpiod_export_link(struct device *dev, const char *name,
 	return -ENOSYS;
 }
 
-static inline int gpiod_sysfs_set_active_low(struct gpio_desc *desc, int value)
-{
-	return -ENOSYS;
-}
-
 static inline void gpiod_unexport(struct gpio_desc *desc)
 {
 }