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| author | Kent Gibson <warthog618@gmail.com> | 2024-06-10 17:21:56 +0800 |
|---|---|---|
| committer | Bartosz Golaszewski <bartosz.golaszewski@linaro.org> | 2024-06-12 14:02:54 +0200 |
| commit | 5ca84d416e1ca82ca068906fc1386f61a57b17f2 (patch) | |
| tree | 71385f4cadb80e52d9be404843990126561a5b1c /Documentation/userspace-api/gpio/gpio-handle-set-line-values-ioctl.rst | |
| parent | 3ff1180a39fbc43ae69d4238e6922c57e3278910 (diff) | |
Documentation: gpio: Clarify effect of active low flag on line values
The documentation does not make sufficiently clear that the uAPI deals with
logical line values, nor does it describe the influence of the active low
flag on the mapping between physical and logical line values.
Clarify the relationship between physical and logical line values and the
effect of the active low flag for ioctls passing line values.
Suggested-by: David C. Rankin <drankinatty@gmail.com>
Signed-off-by: Kent Gibson <warthog618@gmail.com>
Link: https://lore.kernel.org/r/20240610092157.9147-2-warthog618@gmail.com
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Diffstat (limited to 'Documentation/userspace-api/gpio/gpio-handle-set-line-values-ioctl.rst')
| -rw-r--r-- | Documentation/userspace-api/gpio/gpio-handle-set-line-values-ioctl.rst | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/Documentation/userspace-api/gpio/gpio-handle-set-line-values-ioctl.rst b/Documentation/userspace-api/gpio/gpio-handle-set-line-values-ioctl.rst index 0aa05e623a6c..12862132b420 100644 --- a/Documentation/userspace-api/gpio/gpio-handle-set-line-values-ioctl.rst +++ b/Documentation/userspace-api/gpio/gpio-handle-set-line-values-ioctl.rst @@ -36,6 +36,13 @@ Description Set the values of all requested output lines. +The values set are logical, indicating if the line is to be active or inactive. +The ``GPIOHANDLE_REQUEST_ACTIVE_LOW`` flag controls the mapping between logical +values (active/inactive) and physical values (high/low). +If ``GPIOHANDLE_REQUEST_ACTIVE_LOW`` is not set then active is high and +inactive is low. If ``GPIOHANDLE_REQUEST_ACTIVE_LOW`` is set then active is low +and inactive is high. + Only the values of output lines may be set. Attempting to set the value of input lines is an error (**EPERM**). |