GPIO_GET_LINEINFO_WATCH_IOCTL

Warning

This ioctl is part of GPIO Character Device Userspace API (v1) and is obsoleted by GPIO_V2_GET_LINEINFO_WATCH_IOCTL.

Name

GPIO_GET_LINEINFO_WATCH_IOCTL - Enable watching a line for changes to its request state and configuration information.

Synopsis

GPIO_GET_LINEINFO_WATCH_IOCTL

int ioctl(int chip_fd, GPIO_GET_LINEINFO_WATCH_IOCTL, struct gpioline_info *info)

Arguments

chip_fd

The file descriptor of the GPIO character device returned by open().

info

The line_info struct to be populated, with the offset set to indicate the line to watch

Description

Enable watching a line for changes to its request state and configuration information. Changes to line info include a line being requested, released or reconfigured.

Note

Watching line info is not generally required, and would typically only be used by a system monitoring component.

The line info does NOT include the line value.

The line must be requested using GPIO_GET_LINEHANDLE_IOCTL or GPIO_GET_LINEEVENT_IOCTL to access its value, and the line event can monitor a line for events using GPIO_LINEEVENT_DATA_READ.

By default all lines are unwatched when the GPIO chip is opened.

Multiple lines may be watched simultaneously by adding a watch for each.

Once a watch is set, any changes to line info will generate events which can be read from the chip_fd as described in GPIO_LINEINFO_CHANGED_READ.

Adding a watch to a line that is already watched is an error (EBUSY).

Watches are specific to the chip_fd and are independent of watches on the same GPIO chip opened with a separate call to open().

First added in 5.7.

Return Value

On success 0 and info is populated with the current line info.

On error -1 and the errno variable is set appropriately. Common error codes are described in GPIO Error Codes.