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SubjectRe: [PATCH v4 00/13] gpiolib: add an ioctl() for monitoring line status changes
wt., 7 sty 2020 o 11:07 Linus Walleij <> napisał(a):
> 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
> maintainer.

Ha! This may be a problem - there doesn't seem to be one. This is why
I Cc'd Greg.

> 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.

Sure, will do.

> Yours,
> Linus Walleij


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