Commit 166a85e4 authored by Johan Hovold's avatar Johan Hovold Committed by Linus Walleij
Browse files

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: default avatarJohan Hovold <johan@kernel.org>
Reviewed-by: default avatarAlexandre Courbot <acourbot@nvidia.com>
Signed-off-by: default avatarLinus Walleij <linus.walleij@linaro.org>
parent 426577bd

Documentation/gpio/gpio-legacy.txt

+0 −9
Original line number Diff line number Diff line
@@ -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

+0 −8
Original line number Diff line number Diff line
@@ -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

+0 −8
Original line number Diff line number Diff line
@@ -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

+2 −46
Original line number Diff line number Diff line
@@ -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) ^

				!!test_bit(FLAG_TRIG_FALL, &desc->flags))) {

	if (!!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);
@@ -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

+0 −5
Original line number Diff line number Diff line
@@ -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));

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