diff options
Diffstat (limited to 'Documentation/userspace-api/gpio/gpio-lineevent-data-read.rst')
| -rw-r--r-- | Documentation/userspace-api/gpio/gpio-lineevent-data-read.rst | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/Documentation/userspace-api/gpio/gpio-lineevent-data-read.rst b/Documentation/userspace-api/gpio/gpio-lineevent-data-read.rst index 68b8d4f9f604..d1e7e2383b0d 100644 --- a/Documentation/userspace-api/gpio/gpio-lineevent-data-read.rst +++ b/Documentation/userspace-api/gpio/gpio-lineevent-data-read.rst @@ -44,6 +44,11 @@ Edge detection must be enabled for the input line using either both. Edge events are then generated whenever edge interrupts are detected on the input line. +Edges are defined in terms of changes to the logical line value, so an inactive +to active transition is a rising edge. If ``GPIOHANDLE_REQUEST_ACTIVE_LOW`` is +set then logical polarity is the opposite of physical polarity, and +``GPIOEVENT_REQUEST_RISING_EDGE`` then corresponds to a falling physical edge. + The kernel captures and timestamps edge events as close as possible to their occurrence and stores them in a buffer from where they can be read by userspace at its convenience using `read()`. |