generic Precision Time Protocol (gPTP)¶
Overview¶
This gPTP stack supports the protocol and procedures as defined in the IEEE 802.1AS-2011 standard (Timing and Synchronization for Time-Sensitive Applications in Bridged Local Area Networks).
Supported features¶
The stack handles communications and state machines defined in the IEEE 802.1AS-2011 standard. Mandatory requirements for a full-duplex point-to-point link endpoint, as defined in Annex A of the standard, are supported.
The stack is in principle capable of handling communications on multiple network interfaces (also defined as “ports” in the standard) and thus act as a 802.1AS bridge. However, this mode of operation has not been validated on the Zephyr OS.
Supported hardware¶
Although the stack itself is hardware independent, Ethernet frame timestamping support must be enabled in ethernet drivers.
Boards supported:
Native POSIX execution (native_posix) (only usable for simple testing, limited capabilities due to lack of hardware clock)
X86 Emulation (QEMU) (emulated, limited capabilities due to lack of hardware clock)
Enabling the stack¶
The following configuration option must me enabled in prj.conf
file.
Application interfaces¶
Only two Application Interfaces as defined in section 9 of the standard are available:
ClockTargetPhaseDiscontinuity
interface (gptp_register_phase_dis_cb()
)ClockTargetEventCapture
interface (gptp_event_capture()
)
Testing¶
The stack has been informally tested using the OpenAVnu gPTP and Linux ptp4l daemons. The gPTP sample application from the Zephyr source distribution can be used for testing.
API Reference¶
-
group
gptp
generic Precision Time Protocol (gPTP) support
Typedefs
-
typedef void (*
gptp_phase_dis_callback_t
)(uint8_t *gm_identity, uint16_t *time_base, struct gptp_scaled_ns *last_gm_ph_change, double *last_gm_freq_change)¶ Define callback that is called after a phase discontinuity has been sent by the grandmaster.
- Parameters
uint8_t *gm_identity
: A pointer to first element of a ClockIdentity array. The size of the array is GPTP_CLOCK_ID_LEN.uint16_t *gm_time_base
: A pointer to the value of timeBaseIndicator of the current grandmaster.struct scaled_ns *last_gm_ph_change
: A pointer to the value of lastGmPhaseChange received from grandmaster.double *last_gm_freq_change
: A pointer to the value of lastGmFreqChange received from the grandmaster.
Functions
-
void
gptp_register_phase_dis_cb
(struct gptp_phase_dis_cb *phase_dis, gptp_phase_dis_callback_t cb)¶ Register a phase discontinuity callback.
- Parameters
phase_dis
: Caller specified handler for the callback.cb
: Callback to register.
-
void
gptp_unregister_phase_dis_cb
(struct gptp_phase_dis_cb *phase_dis)¶ Unregister a phase discontinuity callback.
- Parameters
phase_dis
: Caller specified handler for the callback.
-
void
gptp_call_phase_dis_cb
(void)¶ Call a phase discontinuity callback function.
-
int
gptp_event_capture
(struct net_ptp_time *slave_time, bool *gm_present)¶ Get gPTP time.
- Return
Error code. 0 if no error.
- Parameters
slave_time
: A pointer to structure where timestamp will be saved.gm_present
: A pointer to a boolean where status of the presence of a grand master will be saved.
-
char *
gptp_sprint_clock_id
(const uint8_t *clk_id, char *output, size_t output_len)¶ Utility function to print clock id to a user supplied buffer.
- Return
Pointer to output buffer
- Parameters
clk_id
: Clock idoutput
: Output bufferoutput_len
: Output buffer len
-
void
gptp_foreach_port
(gptp_port_cb_t cb, void *user_data)¶ Go through all the gPTP ports and call callback for each of them.
- Parameters
cb
: User-supplied callback function to calluser_data
: User specified data
-
struct gptp_domain *
gptp_get_domain
(void)¶ Get gPTP domain.
This contains all the configuration / status of the gPTP domain.
- Return
Pointer to domain or NULL if not found.
-
void
gptp_clk_src_time_invoke
(struct gptp_clk_src_time_invoke_params *arg)¶ This interface is used by the ClockSource entity to provide time to the ClockMaster entity of a time-aware system.
- Parameters
arg
: Current state and parameters of the ClockSource entity.
-
struct
gptp_scaled_ns
¶ - #include <gptp.h>
Scaled Nanoseconds.
-
struct
gptp_uscaled_ns
¶ - #include <gptp.h>
UScaled Nanoseconds.
-
struct
gptp_port_identity
¶ - #include <gptp.h>
Port Identity.
-
struct
gptp_flags
¶ - #include <gptp.h>
-
struct
gptp_hdr
¶ - #include <gptp.h>
-
struct
gptp_phase_dis_cb
¶ - #include <gptp.h>
Phase discontinuity callback structure.
Stores the phase discontinuity callback information. Caller must make sure that the variable pointed by this is valid during the lifetime of registration. Typically this means that the variable cannot be allocated from stack.
-
struct
gptp_clk_src_time_invoke_params
¶ - #include <gptp.h>
ClockSourceTime.invoke function parameters.
Parameters passed by ClockSourceTime.invoke function.
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typedef void (*