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SubjectRe: [PATCH v4 00/13] gpiolib: add an ioctl() for monitoring line status changes
On Tue, Dec 24, 2019 at 1:07 PM Bartosz Golaszewski <> wrote:

> From: Bartosz Golaszewski <>
> When discussing the recent user-space changes with Kent and while working
> on dbus API for libgpiod I noticed that we really don't have any way of
> keeping the line info synchronized between the kernel and user-space
> processes. We can of course periodically re-read the line information or
> even do it every time we want to read a property but this isn't optimal.
> This series adds a new ioctl() that allows user-space to set up a watch on
> the GPIO chardev file-descriptor which can then be polled for events
> emitted by the kernel when the line is requested, released or its status
> changed. This of course doesn't require the line to be requested. Multiple
> user-space processes can watch the same lines.
> This series also includes a variety of minor tweaks & fixes for problems
> discovered during development. For instance it addresses a race-condition
> in current line event fifo.

The patch set overall looks good to me, I don't understand the kfifo
parts but I trust you on this, though we need review from a FIFO

Could you send me a pull request of the first patches before the
FIFO changes start, they are good cleanups on their own, also
it brings down the size of your patch stack.

Linus Walleij

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