GPIO line request

group line_request

Functions allowing interactions with requested lines.

Functions

void gpiod_line_request_release(struct gpiod_line_request *request)

Release the requested lines and free all associated resources.

Parameters:

request – Line request object to release.

const char *gpiod_line_request_get_chip_name(struct gpiod_line_request *request)

Get the name of the chip this request was made on.

Parameters:

request – Line request object.

Returns:

Name the GPIO chip device. The returned pointer is valid for the lifetime of the request object and must not be freed by the caller.

size_t gpiod_line_request_get_num_requested_lines(struct gpiod_line_request *request)

Get the number of lines in the request.

Parameters:

request – Line request object.

Returns:

Number of requested lines.

size_t gpiod_line_request_get_requested_offsets(struct gpiod_line_request *request, unsigned int *offsets, size_t max_offsets)

Get the offsets of the lines in the request.

If max_offsets is lower than the number of lines actually requested (this value can be retrieved using gpiod_line_request_get_num_requested_lines), then only up to max_lines offsets will be stored in offsets.

Parameters:

  • request – Line request object.

  • offsets – Array to store offsets.

  • max_offsets – Number of offsets that can be stored in the offsets array.

Returns:

Number of offsets stored in the offsets array.

enum gpiod_line_value gpiod_line_request_get_value(struct gpiod_line_request *request, unsigned int offset)

Get the value of a single requested line.

Parameters:

  • request – Line request object.

  • offset – The offset of the line of which the value should be read.

Returns:

Returns 1 or 0 on success and -1 on error.

int gpiod_line_request_get_values_subset(struct gpiod_line_request *request, size_t num_values, const unsigned int *offsets, enum gpiod_line_value *values)

Get the values of a subset of requested lines.

Parameters:

  • request – GPIO line request.

  • num_values – Number of lines for which to read values.

  • offsets – Array of offsets identifying the subset of requested lines from which to read values.

  • values – Array in which the values will be stored. Must be sized to hold num_values entries. Each value is associated with the line identified by the corresponding entry in offsets.

Returns:

0 on success, -1 on failure.

int gpiod_line_request_get_values(struct gpiod_line_request *request, enum gpiod_line_value *values)

Get the values of all requested lines.

Parameters:
Returns:

0 on success, -1 on failure.

int gpiod_line_request_set_value(struct gpiod_line_request *request, unsigned int offset, enum gpiod_line_value value)

Set the value of a single requested line.

Parameters:

  • request – Line request object.

  • offset – The offset of the line for which the value should be set.

  • value – Value to set.

Returns:

0 on success, -1 on failure.

int gpiod_line_request_set_values_subset(struct gpiod_line_request *request, size_t num_values, const unsigned int *offsets, const enum gpiod_line_value *values)

Set the values of a subset of requested lines.

Parameters:

  • request – GPIO line request.

  • num_values – Number of lines for which to set values.

  • offsets – Array of offsets, containing the number of entries specified by num_values, identifying the requested lines for which to set values.

  • values – Array of values to set, containing the number of entries specified by num_values. Each value is associated with the line identified by the corresponding entry in offsets.

Returns:

0 on success, -1 on failure.

int gpiod_line_request_set_values(struct gpiod_line_request *request, const enum gpiod_line_value *values)

Set the values of all lines associated with a request.

Parameters:
Returns:

0 on success, -1 on failure.

int gpiod_line_request_reconfigure_lines(struct gpiod_line_request *request, struct gpiod_line_config *config)

Update the configuration of lines associated with a line request.

Note

The new line configuration completely replaces the old.

Note

Any requested lines without overrides are configured to the requested defaults.

Note

Any configured overrides for lines that have not been requested are silently ignored.

Parameters:

  • request – GPIO line request.

  • config – New line config to apply.

Returns:

0 on success, -1 on failure.

int gpiod_line_request_get_fd(struct gpiod_line_request *request)

Get the file descriptor associated with a line request.

Parameters:

request – GPIO line request.

Returns:

The file descriptor associated with the request. This function never fails. The returned file descriptor must not be closed by the caller. Call gpiod_line_request_release to close the file.

int gpiod_line_request_wait_edge_events(struct gpiod_line_request *request, int64_t timeout_ns)

Wait for edge events on any of the requested lines.

Lines must have edge detection set for edge events to be emitted. By default edge detection is disabled.

Parameters:

  • request – GPIO line request.

  • timeout_ns – Wait time limit in nanoseconds. If set to 0, the function returns immediately. If set to a negative number, the function blocks indefinitely until an event becomes available.

Returns:

0 if wait timed out, -1 if an error occurred, 1 if an event is pending.

int gpiod_line_request_read_edge_events(struct gpiod_line_request *request, struct gpiod_edge_event_buffer *buffer, size_t max_events)

Read a number of edge events from a line request.

Note

This function will block if no event was queued for the line request.

Note

Any exising events in the buffer are overwritten. This is not an append operation.

Parameters:

  • request – GPIO line request.

  • buffer – Edge event buffer, sized to hold at least max_events.

  • max_events – Maximum number of events to read.

Returns:

On success returns the number of events read from the file descriptor, on failure return -1.