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SubjectRe: [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 <>
> 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 <>
> ---
> 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?

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