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Message-ID: <CAMRc=MeL9B+oCLb4SFupmBzK5E+JoGfCvtUp-RvYNT=L9i5M1Q@mail.gmail.com>
Date: Sat, 5 Oct 2024 11:34:26 +0200
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Kent Gibson <warthog618@...il.com>
Cc: Linus Walleij <linus.walleij@...aro.org>, linux-gpio@...r.kernel.org,
linux-kernel@...r.kernel.org,
Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: Re: [PATCH 4/5] gpiolib: simplify notifying user-space about line requests
On Sat, Oct 5, 2024 at 5:46 AM Kent Gibson <warthog618@...il.com> wrote:
>
> On Fri, Oct 04, 2024 at 04:43:25PM +0200, Bartosz Golaszewski wrote:
> > From: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
> >
> > Instead of emitting the line state change event on request in three
> > different places, just do it once, closer to the source: in
> > gpiod_request_commit().
> >
> > Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
> > ---
> > drivers/gpio/gpiolib-cdev.c | 6 ------
> > drivers/gpio/gpiolib.c | 4 ++--
> > 2 files changed, 2 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/gpio/gpiolib-cdev.c b/drivers/gpio/gpiolib-cdev.c
> > index b0050250ac3a..f614a981253d 100644
> > --- a/drivers/gpio/gpiolib-cdev.c
> > +++ b/drivers/gpio/gpiolib-cdev.c
> > @@ -372,8 +372,6 @@ static int linehandle_create(struct gpio_device *gdev, void __user *ip)
> > goto out_free_lh;
> > }
> >
> > - gpiod_line_state_notify(desc, GPIO_V2_LINE_CHANGED_REQUESTED);
> > -
> > dev_dbg(&gdev->dev, "registered chardev handle for line %d\n",
> > offset);
>
> This moves the notify to before the desc->flags have been set.
> So the notified will now see the flags as previously set, not what they
> have been requested as.
>
Ah, I got fooled by the libgpiod tests passing. I guess we should
cover that first in tests-kernel-uapi.c.
> That might be acceptible if you subsequently issue GPIO_V2_LINE_CHANGED_CONFIG
> when the flags are set, but that is not done here and you explicitly don't
> notify from here in patch 5 when you add notifying to gpiod_direction_output()
> etc.
>
IMO it doesn't make sense to always emit REQUESTED and CONFIG_CHANGED
events together. The initial config should be part of the request
event. I'll get back to the drawing board.
Bart
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