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From: Bartosz Golaszewski <brgl@bgdev.pl>
To: Linus Walleij <linus.walleij@linaro.org>, Arnd Bergmann <arnd@arndb.de>
Cc: Kent Gibson <warthog618@gmail.com>,
	Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
	"open list:GPIO SUBSYSTEM" <linux-gpio@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Bartosz Golaszewski <bgolaszewski@baylibre.com>
Subject: Re: [RESEND PATCH v6 6/7] gpiolib: add new ioctl() for monitoring changes in line info
Date: Wed, 12 Feb 2020 12:00:42 +0100	[thread overview]
Message-ID: <CAMRc=MfkbJ=zTvgpaxFC7L7APEhfC7J_PcncGaQ_AQUA9uw2Fw@mail.gmail.com> (raw)
In-Reply-To: <CACRpkdZNyCBxQF_pVPGENob5EKZfYjuaNq5bLNA42XjraXzNZg@mail.gmail.com>

śr., 12 lut 2020 o 11:47 Linus Walleij <linus.walleij@linaro.org> napisał(a):
>
> On Tue, Feb 11, 2020 at 10:19 AM Bartosz Golaszewski <brgl@bgdev.pl> wrote:
>
> > From: Bartosz Golaszewski <bgolaszewski@baylibre.com>
> >
> > Currently there is no way for user-space to be informed about changes
> > in status of GPIO lines e.g. when someone else requests the line or its
> > config changes. We can only periodically re-read the line-info. This
> > is fine for simple one-off user-space tools, but any daemon that provides
> > a centralized access to GPIO chips would benefit hugely from an event
> > driven line info synchronization.
> >
> > This patch adds a new ioctl() that allows user-space processes to reuse
> > the file descriptor associated with the character device for watching
> > any changes in line properties. Every such event contains the updated
> > line information.
> >
> > Currently the events are generated on three types of status changes: when
> > a line is requested, when it's released and when its config is changed.
> > The first two are self-explanatory. For the third one: this will only
> > happen when another user-space process calls the new SET_CONFIG ioctl()
> > as any changes that can happen from within the kernel (i.e.
> > set_transitory() or set_debounce()) are of no interest to user-space.
> >
> > Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
>
> Looks good to me. This got really slim and clean after
> the reviews, and I am of course also impressed by the kfifo
> improvement this brings.
>
> Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
>
> A question:
>
> Bartosz, since you know about possible impacts on userspace,
> since this code use the preferred ktime_get_ns() rather than
> ktime_get_ns_real(), what happens if we just patch the other
> event timestamp to use ktime_get_ns() instead, so we use the
> same everywhere?
>
> If it's fine I'd like to just toss in a patch for that as well.
>

Arnd pointed out it would be an incompatible ABI change[1].

However - I asked Khouloud who's working on v2 of the line event
interface to use ktime_get_ns().

Cheers
Bart

[1] https://marc.info/?l=linux-gpio&m=151661955709074&w=2

  reply	other threads:[~2020-02-12 11:00 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-11  9:19 [RESEND PATCH v6 0/7] gpiolib: add an ioctl() for monitoring line status changes Bartosz Golaszewski
2020-02-11  9:19 ` [RESEND PATCH v6 1/7] kfifo: provide noirqsave variants of spinlocked in and out helpers Bartosz Golaszewski
2020-02-11  9:19 ` [RESEND PATCH v6 2/7] kfifo: provide kfifo_is_empty_spinlocked() Bartosz Golaszewski
2020-02-11  9:19 ` [RESEND PATCH v6 3/7] gpiolib: rework the locking mechanism for lineevent kfifo Bartosz Golaszewski
2020-02-11  9:19 ` [RESEND PATCH v6 4/7] gpiolib: emit a debug message when adding events to a full kfifo Bartosz Golaszewski
2020-02-11  9:19 ` [RESEND PATCH v6 5/7] gpiolib: provide a dedicated function for setting lineinfo Bartosz Golaszewski
2020-03-16 16:20   ` Geert Uytterhoeven
2020-03-17 13:40     ` Bartosz Golaszewski
2020-02-11  9:19 ` [RESEND PATCH v6 6/7] gpiolib: add new ioctl() for monitoring changes in line info Bartosz Golaszewski
2020-02-12 10:47   ` Linus Walleij
2020-02-12 11:00     ` Bartosz Golaszewski [this message]
2020-02-20 15:03       ` Linus Walleij
2020-02-20 15:06         ` Bartosz Golaszewski
2020-02-11  9:19 ` [RESEND PATCH v6 7/7] tools: gpio: implement gpio-watch Bartosz Golaszewski
2020-02-12 10:49 ` [RESEND PATCH v6 0/7] gpiolib: add an ioctl() for monitoring line status changes Linus Walleij

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