GPIO_GET_LINEEVENT_IOCTL¶
Warning
This ioctl is part of GPIO Character Device Userspace API (v1) and is obsoleted by GPIO_V2_GET_LINE_IOCTL.
Name¶
GPIO_GET_LINEEVENT_IOCTL - Request a line with edge detection from the kernel.
Synopsis¶
-
GPIO_GET_LINEEVENT_IOCTL¶
int ioctl(int chip_fd, GPIO_GET_LINEEVENT_IOCTL, struct gpioevent_request *request)
Arguments¶
chip_fdThe file descriptor of the GPIO character device returned by open().
requestThe
event_requestspecifying the line to request and its configuration.
Description¶
Request a line with edge detection from the kernel.
On success, the requesting process is granted exclusive access to the line value and may receive events when edges are detected on the line, as described in GPIO_LINEEVENT_DATA_READ.
The state of a line is guaranteed to remain as requested until the returned file descriptor is closed. Once the file descriptor is closed, the state of the line becomes uncontrolled from the userspace perspective, and may revert to its default state.
Requesting a line already in use is an error (EBUSY).
Requesting edge detection on a line that does not support interrupts is an error (ENXIO).
As with the line handle, the bias configuration is best effort.
Closing the chip_fd has no effect on existing line events.
Configuration Rules¶
The following configuration rules apply:
The line event is requested as an input, so no flags specific to output lines,
GPIOHANDLE_REQUEST_OUTPUT, GPIOHANDLE_REQUEST_OPEN_DRAIN, or
GPIOHANDLE_REQUEST_OPEN_SOURCE, may be set.
Only one bias flag, GPIOHANDLE_REQUEST_BIAS_xxx, may be set.
If no bias flags are set then the bias configuration is not changed.
The edge flags, GPIOEVENT_REQUEST_RISING_EDGE and
GPIOEVENT_REQUEST_FALLING_EDGE, may be combined to detect both rising
and falling edges.
Requesting an invalid configuration is an error (EINVAL).
Return Value¶
On success 0 and the request.fd contains the file
descriptor for the request.
On error -1 and the errno variable is set appropriately.
Common error codes are described in GPIO Error Codes.