Definitions and functions for retrieving kernel information about both requested and free lines. More...
Enumerations | |
| enum | { GPIOD_LINE_DIRECTION_INPUT = 1, GPIOD_LINE_DIRECTION_OUTPUT } |
| Possible direction settings. More... | |
| enum | { GPIOD_LINE_ACTIVE_STATE_HIGH = 1, GPIOD_LINE_ACTIVE_STATE_LOW } |
| Possible active state settings. More... | |
| enum | { GPIOD_LINE_BIAS_AS_IS = 1, GPIOD_LINE_BIAS_DISABLE, GPIOD_LINE_BIAS_PULL_UP, GPIOD_LINE_BIAS_PULL_DOWN } |
| Possible internal bias settings. More... | |
Functions | |
| unsigned int | gpiod_line_offset (struct gpiod_line *line) GPIOD_API |
| Read the GPIO line offset. More... | |
| const char * | gpiod_line_name (struct gpiod_line *line) GPIOD_API |
| Read the GPIO line name. More... | |
| const char * | gpiod_line_consumer (struct gpiod_line *line) GPIOD_API |
| Read the GPIO line consumer name. More... | |
| int | gpiod_line_direction (struct gpiod_line *line) GPIOD_API |
| Read the GPIO line direction setting. More... | |
| int | gpiod_line_active_state (struct gpiod_line *line) GPIOD_API |
| Read the GPIO line active state setting. More... | |
| int | gpiod_line_bias (struct gpiod_line *line) GPIOD_API |
| Read the GPIO line bias setting. More... | |
| bool | gpiod_line_is_used (struct gpiod_line *line) GPIOD_API |
| Check if the line is currently in use. More... | |
| bool | gpiod_line_is_open_drain (struct gpiod_line *line) GPIOD_API |
| Check if the line is an open-drain GPIO. More... | |
| bool | gpiod_line_is_open_source (struct gpiod_line *line) GPIOD_API |
| Check if the line is an open-source GPIO. More... | |
| int | gpiod_line_update (struct gpiod_line *line) GPIOD_API |
| Re-read the line info. More... | |
| bool | gpiod_line_needs_update (struct gpiod_line *line) GPIOD_API GPIOD_DEPRECATED |
| Check if the line info needs to be updated. More... | |
Detailed Description
Definitions and functions for retrieving kernel information about both requested and free lines.
Enumeration Type Documentation
◆ anonymous enum
| anonymous enum |
◆ anonymous enum
| anonymous enum |
◆ anonymous enum
| anonymous enum |
Function Documentation
◆ gpiod_line_active_state()
| int gpiod_line_active_state | ( | struct gpiod_line * | line | ) |
Read the GPIO line active state setting.
- Parameters
-
line GPIO line object.
- Returns
- Returns GPIOD_LINE_ACTIVE_STATE_HIGH or GPIOD_LINE_ACTIVE_STATE_LOW.
◆ gpiod_line_bias()
| int gpiod_line_bias | ( | struct gpiod_line * | line | ) |
Read the GPIO line bias setting.
- Parameters
-
line GPIO line object.
- Returns
- Returns GPIOD_LINE_BIAS_PULL_UP, GPIOD_LINE_BIAS_PULL_DOWN, GPIOD_LINE_BIAS_DISABLE or GPIOD_LINE_BIAS_AS_IS.
◆ gpiod_line_consumer()
| const char* gpiod_line_consumer | ( | struct gpiod_line * | line | ) |
Read the GPIO line consumer name.
- Parameters
-
line GPIO line object.
- Returns
- Name of the GPIO consumer name as it is represented in the kernel. This routine returns a pointer to a null-terminated string or NULL if the line is not used.
◆ gpiod_line_direction()
| int gpiod_line_direction | ( | struct gpiod_line * | line | ) |
Read the GPIO line direction setting.
- Parameters
-
line GPIO line object.
- Returns
- Returns GPIOD_LINE_DIRECTION_INPUT or GPIOD_LINE_DIRECTION_OUTPUT.
◆ gpiod_line_is_open_drain()
| bool gpiod_line_is_open_drain | ( | struct gpiod_line * | line | ) |
Check if the line is an open-drain GPIO.
- Parameters
-
line GPIO line object.
- Returns
- True if the line is an open-drain GPIO, false otherwise.
◆ gpiod_line_is_open_source()
| bool gpiod_line_is_open_source | ( | struct gpiod_line * | line | ) |
Check if the line is an open-source GPIO.
- Parameters
-
line GPIO line object.
- Returns
- True if the line is an open-source GPIO, false otherwise.
◆ gpiod_line_is_used()
| bool gpiod_line_is_used | ( | struct gpiod_line * | line | ) |
Check if the line is currently in use.
- Parameters
-
line GPIO line object.
- Returns
- True if the line is in use, false otherwise.
The user space can't know exactly why a line is busy. It may have been requested by another process or hogged by the kernel. It only matters that the line is used and we can't request it.
◆ gpiod_line_name()
| const char* gpiod_line_name | ( | struct gpiod_line * | line | ) |
Read the GPIO line name.
- Parameters
-
line GPIO line object.
- Returns
- Name of the GPIO line as it is represented in the kernel. This routine returns a pointer to a null-terminated string or NULL if the line is unnamed.
◆ gpiod_line_needs_update()
| bool gpiod_line_needs_update | ( | struct gpiod_line * | line | ) |
Check if the line info needs to be updated.
- Parameters
-
line GPIO line object.
- Returns
- Always returns false.
- Deprecated:
- This mechanism no longer exists in the library and this function does nothing.
References GPIOD_LINE_REQUEST_DIRECTION_AS_IS, GPIOD_LINE_REQUEST_DIRECTION_INPUT, GPIOD_LINE_REQUEST_DIRECTION_OUTPUT, GPIOD_LINE_REQUEST_EVENT_BOTH_EDGES, GPIOD_LINE_REQUEST_EVENT_FALLING_EDGE, and GPIOD_LINE_REQUEST_EVENT_RISING_EDGE.
◆ gpiod_line_offset()
| unsigned int gpiod_line_offset | ( | struct gpiod_line * | line | ) |
Read the GPIO line offset.
- Parameters
-
line GPIO line object.
- Returns
- Line offset.
◆ gpiod_line_update()
| int gpiod_line_update | ( | struct gpiod_line * | line | ) |
Re-read the line info.
- Parameters
-
line GPIO line object.
- Returns
- 0 if the operation succeeds. In case of an error this routine returns -1 and sets the last error number.
The line info is initially retrieved from the kernel by gpiod_chip_get_line() and is later re-read after every successful request. Users can use this function to manually re-read the line info when needed.
We currently have no mechanism provided by the kernel for keeping the line info synchronized and for the sake of speed and simplicity of this low-level library we don't want to re-read the line info automatically everytime a property is retrieved. Any daemon using this library must track the state of lines on its own and call this routine if needed.
The state of requested lines is kept synchronized (or rather cannot be changed by external agents while the ownership of the line is taken) so there's no need to call this function in that case.
