diff options
| author | Johan Hovold <johan@kernel.org> | 2015-05-04 17:10:33 +0200 |
|---|---|---|
| committer | Linus Walleij <linus.walleij@linaro.org> | 2015-05-12 10:46:53 +0200 |
| commit | 166a85e44245d771bd7042f3ad72aa0e12bb53bd (patch) | |
| tree | a9fd0409715c50ff15d2314b2314b4358c754ffb /Documentation/gpio/sysfs.txt | |
| parent | gpio: sysfs: rename gpiochip registration functions (diff) | |
| download | linux-166a85e44245d771bd7042f3ad72aa0e12bb53bd.tar.xz linux-166a85e44245d771bd7042f3ad72aa0e12bb53bd.zip | |
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>
Diffstat (limited to 'Documentation/gpio/sysfs.txt')
| -rw-r--r-- | Documentation/gpio/sysfs.txt | 8 |
1 files changed, 0 insertions, 8 deletions
diff --git a/Documentation/gpio/sysfs.txt b/Documentation/gpio/sysfs.txt index c2c3a97f8ff7..535b6a8a7a7c 100644 --- a/Documentation/gpio/sysfs.txt +++ b/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. |