linux-kernel - Re: [PATCH v3 12/13] gpiolib: add new ioctl() for monitoring changes in line info

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Message-ID: <CAMRc=McM6VeOHj5hhk5bLoc=Vy3LTnuoCt-18s8BFOZDbChqqw@mail.gmail.com>
Date:   Fri, 20 Dec 2019 09:45:53 +0100
From:   Bartosz Golaszewski <brgl@...ev.pl>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Kent Gibson <warthog618@...il.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>
Subject: Re: [PATCH v3 12/13] gpiolib: add new ioctl() for monitoring changes
 in line info

czw., 19 gru 2019 o 18:24 Greg Kroah-Hartman
<gregkh@...uxfoundation.org> napisał(a):
>
> On Thu, Dec 19, 2019 at 06:15:27PM +0100, Bartosz Golaszewski wrote:
> > From: Bartosz Golaszewski <bgolaszewski@...libre.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@...libre.com>
> > ---
> >  drivers/gpio/gpiolib.c    | 191 ++++++++++++++++++++++++++++++++++++--
> >  drivers/gpio/gpiolib.h    |   1 +
> >  include/uapi/linux/gpio.h |  24 +++++
> >  tools/gpio/gpio-watch     | Bin 0 -> 26528 bytes
>
> Did you mean for this binary file to be checked in?
>

No, of course not, it's a mistake. I'll remove it in v4.

Bart