From: Linus Walleij <linus.walleij@linaro.org>
To: Arnd Bergmann <arnd@arndb.de>
Cc: Bartosz Golaszewski <brgl@bgdev.pl>,
linux-gpio@vger.kernel.org,
Andy Shevchenko <andy.shevchenko@gmail.com>,
Clemens Gruber <clemens.gruber@pqgruber.com>,
Thierry Reding <thierry.reding@gmail.com>,
Peter Rosin <peda@axentia.se>,
Lars-Peter Clausen <lars@metafoo.de>
Subject: Re: [RFC] libgpiod public API reviews needed
Date: Mon, 22 Jan 2018 09:21:00 +0100 [thread overview]
Message-ID: <CACRpkdbJUOvNDwM=wZw5iLwPAf-D+i27E9JRzV=Gr0mnZbX3kg@mail.gmail.com> (raw)
In-Reply-To: <CAK8P3a1JeOREOXWz+BBurs3odtDTGEUnpotbLEZEOsX7YUNfeA@mail.gmail.com>
On Sun, Jan 21, 2018 at 11:18 PM, Arnd Bergmann <arnd@arndb.de> wrote:
> On Sun, Jan 21, 2018 at 10:30 PM, Bartosz Golaszewski <brgl@bgdev.pl> wrote:
>> 2018-01-21 16:49 GMT+01:00 Linus Walleij <linus.walleij@linaro.org>:
>>> On Fri, Jan 19, 2018 at 2:28 PM, Bartosz Golaszewski <brgl@bgdev.pl> wrote:
>
>> I was not aware of this, but it seems you're right! Nice catch, thanks.
>>
>> How about defining a local struct gpiod_timespec with both seconds and
>> nanoseconds explicitly defined to uint64_t?
>
> Where is that timestamp generated? Is this purely a user space interface
> with the time read from gettimeofday(), or are we talking about a new
> kernel-to-user interface?
This is in include/uapi/linux/gpio.h:
/**
* struct gpioevent_data - The actual event being pushed to userspace
* @timestamp: best estimate of time of event occurrence, in nanoseconds
* @id: event identifier
*/
struct gpioevent_data {
__u64 timestamp;
__u32 id;
};
It is the same as is used for IIO. Inside the kernel this ultimately
comes from ktime_get_real_ns();
> In a lot of cases, a simple 64-bit nanosecond counter using CLOCK_MONOTONIC
> timestamps is the most robust and simple solution.
Bartosz also seems to think it is the best so would vote to go
for that and we have one problem less.
Yours,
Linus Walleij
next prev parent reply other threads:[~2018-01-22 8:21 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-19 13:28 [RFC] libgpiod public API reviews needed Bartosz Golaszewski
2018-01-20 16:02 ` Clemens Gruber
2018-01-21 21:14 ` Bartosz Golaszewski
2018-01-21 15:49 ` Linus Walleij
2018-01-21 21:30 ` Bartosz Golaszewski
2018-01-21 22:18 ` Arnd Bergmann
2018-01-22 8:21 ` Linus Walleij [this message]
2018-01-22 9:25 ` Arnd Bergmann
2018-01-22 9:28 ` Arnd Bergmann
2018-01-22 11:02 ` Bartosz Golaszewski
2018-01-22 11:12 ` Arnd Bergmann
2018-01-23 15:14 ` Bartosz Golaszewski
2018-01-22 12:02 ` Linus Walleij
2018-01-22 13:46 ` Arnd Bergmann
2018-01-23 14:15 ` Ludovic Desroches
2018-01-23 15:05 ` Bartosz Golaszewski
2018-01-25 16:29 ` Bartosz Golaszewski
2018-01-26 7:35 ` Ludovic Desroches
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