diff options
Diffstat (limited to 'Documentation/driver-api')
| -rw-r--r-- | Documentation/driver-api/gpio/driver.rst | 8 | ||||
| -rw-r--r-- | Documentation/driver-api/gpio/legacy.rst | 23 |
2 files changed, 4 insertions, 27 deletions
diff --git a/Documentation/driver-api/gpio/driver.rst b/Documentation/driver-api/gpio/driver.rst index 6baaeab79534..bf6319cc531b 100644 --- a/Documentation/driver-api/gpio/driver.rst +++ b/Documentation/driver-api/gpio/driver.rst @@ -218,10 +218,10 @@ not support open drain/open source in hardware, the GPIO library will instead use a trick: when a line is set as output, if the line is flagged as open drain, and the IN output value is low, it will be driven low as usual. But if the IN output value is set to high, it will instead *NOT* be driven high, -instead it will be switched to input, as input mode is high impedance, thus -achieving an "open drain emulation" of sorts: electrically the behaviour will -be identical, with the exception of possible hardware glitches when switching -the mode of the line. +instead it will be switched to input, as input mode is an equivalent to +high impedance, thus achieving an "open drain emulation" of sorts: electrically +the behaviour will be identical, with the exception of possible hardware glitches +when switching the mode of the line. For open source configuration the same principle is used, just that instead of actively driving the line low, it is set to input. diff --git a/Documentation/driver-api/gpio/legacy.rst b/Documentation/driver-api/gpio/legacy.rst index a0559d93efd1..78372853c6d4 100644 --- a/Documentation/driver-api/gpio/legacy.rst +++ b/Documentation/driver-api/gpio/legacy.rst @@ -238,8 +238,6 @@ setup or driver probe/teardown code, so this is an easy constraint.):: ## gpio_free_array() gpio_free() - gpio_set_debounce() - Claiming and Releasing GPIOs @@ -716,27 +714,6 @@ gpiochip nodes (possibly in conjunction with schematics) to determine the correct GPIO number to use for a given signal. -Exporting from Kernel code --------------------------- -Kernel code can explicitly manage exports of GPIOs which have already been -requested using gpio_request():: - - /* export the GPIO to userspace */ - int gpio_export(unsigned gpio, bool direction_may_change); - - /* reverse gpio_export() */ - void gpio_unexport(); - -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 -from accidentally clobbering important system state. - -This explicit exporting can help with debugging (by making some kinds -of experiments easier), or can provide an always-there interface that's -suitable for documenting as part of a board support package. - - API Reference ============= |