diff options
| author | Linus Walleij <linus.walleij@linaro.org> | 2020-02-20 15:56:24 +0100 |
|---|---|---|
| committer | Linus Walleij <linus.walleij@linaro.org> | 2020-02-21 16:29:38 +0100 |
| commit | f8850206e160bfe35de9ca2e726ab6d6b8cb77dd (patch) | |
| tree | 544a8700772a327087c3a86815d2a8a465842ad2 /drivers | |
| parent | 1739a2d852265977836152be43073ead5c64d1ea (diff) | |
gpio: Switch timestamps to ktime_get_ns()
The existing use of ktime_get_real_ns() in the timestamps from
the GPIO events is dubious.
We have had several discussions about this timestamp, and it is
unclear whether userspace has ever taken into account that a
timestamp from ktime_get_real_ns() can actually move backwards
in time relative the previous timetamp, and userspace is more
likely to expect a monotonic counter.
Background:
https://lore.kernel.org/linux-gpio/CAK8P3a1Skvm48sje8FNDPLYqyz9Lf8q0qX1QETWtyZTxuX4k1g@mail.gmail.com/
https://marc.info/?l=linux-gpio&m=151661955709074&w=2
The change is ABI incompatible, but incompatible in a way that
is IMO more likely to fix future bugs rather than break current
userspace. To the best of my knowledge all userspace expects
a monotonic timestamp and users are just lucky that they very
seldom move backwards in time.
Cc: Arnd Bergmann <arnd@arndb.de>
Acked-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/gpio/gpiolib.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c index 611709fd560f..2c3a9c1c76be 100644 --- a/drivers/gpio/gpiolib.c +++ b/drivers/gpio/gpiolib.c @@ -954,7 +954,7 @@ static irqreturn_t lineevent_irq_thread(int irq, void *p) * we didn't get the timestamp from lineevent_irq_handler(). */ if (!le->timestamp) - ge.timestamp = ktime_get_real_ns(); + ge.timestamp = ktime_get_ns(); else ge.timestamp = le->timestamp; @@ -995,7 +995,7 @@ static irqreturn_t lineevent_irq_handler(int irq, void *p) * Just store the timestamp in hardirq context so we get it as * close in time as possible to the actual event. */ - le->timestamp = ktime_get_real_ns(); + le->timestamp = ktime_get_ns(); return IRQ_WAKE_THREAD; } |