linux-kernel - Re: [PATCH v5 0/7] gpiolib: add an ioctl() for monitoring line status changes

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Date:   Thu, 23 Jan 2020 11:15:05 +0100
From:   Bartosz Golaszewski <brgl@...ev.pl>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Kent Gibson <warthog618@...il.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Linus Walleij <linus.walleij@...aro.org>
Subject: Re: [PATCH v5 0/7] gpiolib: add an ioctl() for monitoring line status changes

wt., 14 sty 2020 o 08:44 Bartosz Golaszewski <brgl@...ev.pl> napisał(a):
>
> czw., 9 sty 2020 o 12:50 Bartosz Golaszewski <brgl@...ev.pl> napisał(a):
> >
> > From: Bartosz Golaszewski <bgolaszewski@...libre.com>
> >
> > 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.
> >
> > First two patches add new helpers to kfifo, that are used in the later
> > parts of the series.
> >
> > v1: https://lkml.org/lkml/2019/11/27/327
> >
> > v1 -> v2:
> > - rework the main patch of the series: re-use the existing file-descriptor
> >   associated with an open character device
> > - add a patch adding a debug message when the line event kfifo is full and
> >   we're discarding another event
> > - rework the locking mechanism for lineevent kfifo: reuse the spinlock
> >   from the waitqueue structure
> > - other minor changes
> >
> > v2 -> v3:
> > - added patches providing new implementation for some kfifo macros
> > - fixed a regression in the patch reworking the line event fifo: reading
> >   multiple events is now still possible
> > - reworked the structure for new ioctl: it's now padded such that there
> >   be no alignment issues if running a 64-bit kernel on 32-bit userspace
> > - fixed a bug where one process could disable the status watch of another
> > - use kstrtoul() instead of atoi() in gpio-watch for string validation
> >
> > v3 -> v4:
> > - removed a binary file checked in by mistake
> > - drop __func__ from debug messages
> > - restructure the code in the notifier call
> > - add comments about the alignment of the new uAPI structure
> > - remove a stray new line that doesn't belong in this series
> > - tested the series on 32-bit user-space with 64-bit kernel
> >
> > v4 -> v5:
> > - dropped patches already merged upstream
> > - collected review tags
> >
> > Bartosz Golaszewski (7):
> >   kfifo: provide noirqsave variants of spinlocked in and out helpers
> >   kfifo: provide kfifo_is_empty_spinlocked()
> >   gpiolib: rework the locking mechanism for lineevent kfifo
> >   gpiolib: emit a debug message when adding events to a full kfifo
> >   gpiolib: provide a dedicated function for setting lineinfo
> >   gpiolib: add new ioctl() for monitoring changes in line info
> >   tools: gpio: implement gpio-watch
>
> Hi Andrew,
>
> could you Ack the first two patches in this series if you're fine with
> them? The code they modify lives in lib/ and doesn't have an assigned
> maintainer, so I've been told to Cc you on this series. It would be
> great if we could get it in for v5.6 merge window.
>
> Best regards,
> Bartosz Golaszewski

Gentle ping.

Greg: could you maybe ack the kfifo patches so that we can get this in for v5.6?

Bart