time_pps_create().
This implies that the source has a /dev/... entry. This assumption is
-ok for the serial and parallel port, where you can do something
+OK for the serial and parallel port, where you can do something
useful besides(!) the gathering of timestamps as it is the central
-task for a PPS-API. But this assumption does not work for a single
+task for a PPS API. But this assumption does not work for a single
purpose GPIO line. In this case even basic file-related functionality
(like read() and write()) makes no sense at all and should not be a
-precondition for the use of a PPS-API.
+precondition for the use of a PPS API.
The problem can be simply solved if you consider that a PPS source is
not always connected with a GPS data source.
--------------
To register a PPS source into the kernel you should define a struct
-pps_source_info_s as follows:
+pps_source_info as follows:
static struct pps_source_info pps_ktimer_info = {
.name = "ktimer",
.path = "",
- .mode = PPS_CAPTUREASSERT | PPS_OFFSETASSERT | \
- PPS_ECHOASSERT | \
+ .mode = PPS_CAPTUREASSERT | PPS_OFFSETASSERT |
+ PPS_ECHOASSERT |
PPS_CANWAIT | PPS_TSFMT_TSPEC,
.echo = pps_ktimer_echo,
.owner = THIS_MODULE,
The pps_register_source() prototype is:
- int pps_register_source(struct pps_source_info_s *info, int default_params)
+ int pps_register_source(struct pps_source_info *info, int default_params)
where "info" is a pointer to a structure that describes a particular
PPS source, "default_params" tells the system what the initial default
parameters for the device should be (it is obvious that these parameters
must be a subset of ones defined in the struct
-pps_source_info_s which describe the capabilities of the driver).
+pps_source_info which describe the capabilities of the driver).
Once you have registered a new PPS source into the system you can
signal an assert event (for example in the interrupt handler routine)
Every directory is the ID of a PPS sources defined in the system and
inside you find several files:
- $ ls /sys/class/pps/pps0/
- assert clear echo mode name path subsystem@ uevent
+ $ ls -F /sys/class/pps/pps0/
+ assert dev mode path subsystem@
+ clear echo name power/ uevent
+
Inside each "assert" and "clear" file you can find the timestamp and a
sequence number:
Where before the "#" is the timestamp in seconds; after it is the
sequence number. Other files are:
-* echo: reports if the PPS source has an echo function or not;
+ * echo: reports if the PPS source has an echo function or not;
-* mode: reports available PPS functioning modes;
+ * mode: reports available PPS functioning modes;
-* name: reports the PPS source's name;
+ * name: reports the PPS source's name;
-* path: reports the PPS source's device path, that is the device the
- PPS source is connected to (if it exists).
+ * path: reports the PPS source's device path, that is the device the
+ PPS source is connected to (if it exists).
Testing the PPS support
-----------------------
In order to test the PPS support even without specific hardware you can use
-the ktimer driver (see the client subsection in the PPS configuration menu)
+the pps-ktimer driver (see the client subsection in the PPS configuration menu)
and the userland tools available in your distribution's pps-tools package,
-http://linuxpps.org , or https://github.com/ago/pps-tools .
+http://linuxpps.org , or https://github.com/redlab-i/pps-tools.
-Once you have enabled the compilation of ktimer just modprobe it (if
+Once you have enabled the compilation of pps-ktimer just modprobe it (if
not statically compiled):
- # modprobe ktimer
+ # modprobe pps-ktimer
and the run ppstest as follow:
- $ ./ppstest /dev/pps0
+ $ ./ppstest /dev/pps1
trying PPS source "/dev/pps1"
found PPS source "/dev/pps1"
ok, found 1 source(s), now start fetching data...
source 0 - assert 1186592700.388931295, sequence: 365 - clear 0.000000000, sequence: 0
source 0 - assert 1186592701.389032765, sequence: 366 - clear 0.000000000, sequence: 0
-Please, note that to compile userland programs you need the file timepps.h .
+Please note that to compile userland programs, you need the file timepps.h.
This is available in the pps-tools repository mentioned above.
#define LINUX_PPS_KERNEL_H
#include <linux/pps.h>
-
#include <linux/cdev.h>
#include <linux/device.h>
#include <linux/time.h>
/* The specific PPS source info */
struct pps_source_info {
- char name[PPS_MAX_NAME_LEN]; /* simbolic name */
+ char name[PPS_MAX_NAME_LEN]; /* symbolic name */
char path[PPS_MAX_NAME_LEN]; /* path of connected device */
- int mode; /* PPS's allowed mode */
+ int mode; /* PPS allowed mode */
void (*echo)(struct pps_device *pps,
int event, void *data); /* PPS echo function */
struct pps_device {
struct pps_source_info info; /* PSS source info */
- struct pps_kparams params; /* PPS's current params */
+ struct pps_kparams params; /* PPS current params */
- __u32 assert_sequence; /* PPS' assert event seq # */
- __u32 clear_sequence; /* PPS' clear event seq # */
+ __u32 assert_sequence; /* PPS assert event seq # */
+ __u32 clear_sequence; /* PPS clear event seq # */
struct pps_ktime assert_tu;
struct pps_ktime clear_tu;
int current_mode; /* PPS mode at event time */
wait_queue_head_t queue; /* PPS event queue */
unsigned int id; /* PPS source unique ID */
- void const *lookup_cookie; /* pps_lookup_dev only */
+ void const *lookup_cookie; /* For pps_lookup_dev() only */
struct cdev cdev;
struct device *dev;
struct fasync_struct *async_queue; /* fasync method */
extern void pps_unregister_source(struct pps_device *pps);
extern void pps_event(struct pps_device *pps,
struct pps_event_time *ts, int event, void *data);
-/* Look up a pps device by magic cookie */
+/* Look up a pps_device by magic cookie */
struct pps_device *pps_lookup_dev(void const *cookie);
static inline void timespec_to_pps_ktime(struct pps_ktime *kt,
}
#endif /* LINUX_PPS_KERNEL_H */
-
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