Messages in this thread Patch in this message | | | Subject | [PATCH 2.6.14-rc3] evded: timestamping with monotonic time (+ configuration ioctl) | From | (Michal Maruška) | Date | Thu, 06 Oct 2005 14:50:10 +0200 |
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For my modification of XFree86 keyboard event handling I need to detect *duration* of key presses, i.e. difference in time between 2 input events.
Evdev, in current version, timestamps each event with do_gettimeofday(). In presence of adjustements to timeofday the difference/duration information is damaged.
I would like to read the events timestamped with do_posix_clock_monotonic_gettime() time.
I have prepared a patch, which provides an IOCTL call with which a reader can request this monotonic timestamp. The default behaviour remains unchanged (I think useless).
What i am not sure about:
* evdev builds as module, so do_posix_clock_monotonic_gettime is needed exported... so my patch adds EXPORT_SYMBOL_GPL(do_posix_clock_monotonic_gettime) in kernel/posix-timers.c.
* _IOW macro to declare the ioctl number I took just a successor of the highest pre-existant number.
* I don't know how interrupt handlers preempt one another. So, in my attempt to attain the most precise timestamp, I would like the interrupt routine to ask for the timestamp as soon as possible. I could prepare another patch, which adds to each "struct input_dev" a slot where the timestamp is stored at the beginning of the interrupt routine. Evdev then uses such timestamp, if the lower-level driver provides it.
Signed-off-by: Michal Maruska <mmc@maruska.dyndns.org>
--- linux-2.6.14-rc3.orig/drivers/input/evdev.c 2005-10-05 22:47:40.000000000 +0200 +++ linux-2.6.14-rc3.mmc/drivers/input/evdev.c 2005-10-06 14:27:16.084510018 +0200 @@ -38,6 +38,7 @@ struct input_event buffer[EVDEV_BUFFER_SIZE]; int head; int tail; + int time_kind; /* which time to use for the timestamps. Monotonic or timeofday */ struct fasync_struct *fasync; struct evdev *evdev; struct list_head node; @@ -45,15 +46,37 @@ static struct evdev *evdev_table[EVDEV_MINORS]; +static inline +void +mem_copy_time(struct timeval *a, struct timeval* b) +{ + memcpy(a, b, sizeof(struct timeval)); +} + static void evdev_event(struct input_handle *handle, unsigned int type, unsigned int code, int value) { struct evdev *evdev = handle->private; struct evdev_list *list; + struct timeval mtv, dtv; + /* `do_posix_clock_monotonic_gettime' delivers a different struct, + * but i do the conversion immediately, and once. */ + struct timespec mts; + + do_posix_clock_monotonic_gettime(&mts); + mtv.tv_sec = mts.tv_sec; + mtv.tv_usec = mts.tv_nsec / 1000; /* should I >> 10 ? */ + + do_gettimeofday(&dtv); /* for backward compatibility: */ + if (evdev->grab) { list = evdev->grab; - do_gettimeofday(&list->buffer[list->head].time); + if (list->time_kind == EV_USE_DAY_TIME) + mem_copy_time(&list->buffer[list->head].time,&dtv); + else + mem_copy_time(&list->buffer[list->head].time,&mtv); + list->buffer[list->head].type = type; list->buffer[list->head].code = code; list->buffer[list->head].value = value; @@ -63,7 +86,11 @@ } else list_for_each_entry(list, &evdev->list, node) { - do_gettimeofday(&list->buffer[list->head].time); + if (list->time_kind == EV_USE_DAY_TIME) + mem_copy_time(&list->buffer[list->head].time,&dtv); + else + mem_copy_time(&list->buffer[list->head].time,&mtv); + list->buffer[list->head].type = type; list->buffer[list->head].code = code; list->buffer[list->head].value = value; @@ -135,6 +162,7 @@ return -ENOMEM; memset(list, 0, sizeof(struct evdev_list)); + list->time_kind = EV_USE_DAY_TIME; /* for backward compatibility! */ list->evdev = evdev_table[i]; list_add_tail(&list->node, &evdev_table[i]->list); file->private_data = list; @@ -371,6 +399,17 @@ evdev->grab = NULL; return 0; } + case EVIOCTIME: + switch (arg) { + case EV_USE_MONOTONIC_TIME: + list->time_kind = EV_USE_MONOTONIC_TIME; + return 0; + case EV_USE_DAY_TIME: + list->time_kind = EV_USE_DAY_TIME; + return 0; + default: + return -EINVAL; + } default: --- linux-2.6.14-rc3.orig/include/linux/input.h 2005-10-05 23:07:39.833168000 +0200 +++ linux-2.6.14-rc3.mmc/include/linux/input.h 2005-10-05 22:47:40.000000000 +0200 @@ -78,6 +78,15 @@ #define EVIOCGRAB _IOW('E', 0x90, int) /* Grab/Release device */ +#define EVIOCTIME _IOW('E', 0x91, int) /* choose what kind of time to use for timestamps */ + +/* + * Time used to timestamp + */ +#define EV_USE_MONOTONIC_TIME 0 +#define EV_USE_DAY_TIME 1 + + /* * Event types */ --- linux-2.6.14-rc3/kernel/posix-timers.c 2005-10-05 23:07:40.295183000 +0200 +++ linux-2.6.14-rc3.mmc/kernel/posix-timers.c 2005-10-06 14:30:30.831829116 +0200 @@ -1223,6 +1223,7 @@ { return do_posix_clock_monotonic_get(CLOCK_MONOTONIC, tp); } +EXPORT_SYMBOL_GPL(do_posix_clock_monotonic_gettime); int do_posix_clock_nosettime(clockid_t clockid, struct timespec *tp) { - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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