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

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Date:   Thu, 19 Dec 2019 18:24:14 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Bartosz Golaszewski <brgl@...ev.pl>
Cc:     Kent Gibson <warthog618@...il.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        linux-gpio@...r.kernel.org, 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

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?