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From: Kent Gibson <warthog618@gmail.com>
To: Linus Walleij <linus.walleij@linaro.org>
Cc: Bartosz Golaszewski <brgl@bgdev.pl>, Drew Fustini <drew@pdp7.com>,
	"open list:GPIO SUBSYSTEM" <linux-gpio@vger.kernel.org>,
	Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Subject: Re: [RFC] gpio: expose pull-up/pull-down line flags to userspace
Date: Sun, 6 Oct 2019 11:12:20 +0800
Message-ID: <20191006031220.GA7957@sol> (raw)
In-Reply-To: <CACRpkdZP8GYPUk4ZB+2Ei4hrrT0Orq0MUEszJ+YM=npuh1uH9w@mail.gmail.com>

On Sat, Oct 05, 2019 at 07:02:58PM +0200, Linus Walleij wrote:
> On Fri, Oct 4, 2019 at 9:22 AM Bartosz Golaszewski <brgl@bgdev.pl> wrote:
> 
> > The config ioctl (or
> > something similar) you're mentioning may appear sooner actually -
> > users of libgpiod have been requesting a way of changing the direction
> > of a line without releasing it - something that's possible in the
> > kernel, but not from user-space at the moment. I'll submit something
> > that allows to change the configuration of a requested line soon.
> 
> Hm! I guess I assumed that userspace users would be using the lines
> for either input or output, not complex use cases like that, reversing
> direction and what not.
> 
> What kind of usecase is this? I certainly hope nothing like doing
> userspace drivers for complex hardware ... those should be in
> the kernel... the current ABI is a bit oriented around industrial
> automation and prototyping use cases.
> 
I'm not the only one asking for this, and I can't speak to others' use
cases, but in my case I'm prototyping and bit bashing a SPI driver for
an ADC where the MOSI/MISO lines can be tied to save a pin. I need to
be able to switch line direction without glitching the line and that
can't be guaranteed with the current UAPI.

Would you consider that "complex hardware"?

Kent.

  reply index

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-21 10:25 Drew Fustini
2019-09-23  8:38 ` Bartosz Golaszewski
2019-10-02 11:10   ` Drew Fustini
2019-10-03 12:47   ` Linus Walleij
2019-10-04  7:22     ` Bartosz Golaszewski
2019-10-04 12:46       ` Bartosz Golaszewski
2019-10-05 17:02       ` Linus Walleij
2019-10-06  3:12         ` Kent Gibson [this message]
2019-10-06 21:06           ` Linus Walleij
2019-10-07  4:37             ` Kent Gibson
2019-10-08  6:15 ` Kent Gibson
2019-10-08 20:56   ` Bartosz Golaszewski
2019-10-08 23:21     ` Kent Gibson
2019-10-08 23:30       ` Bartosz Golaszewski
2019-10-08 23:56         ` Kent Gibson
2019-10-09  0:03           ` Bartosz Golaszewski
2019-10-09  0:22             ` Kent Gibson
2019-10-09  6:55               ` Kent Gibson
2019-10-09 12:57                 ` Drew Fustini
2019-10-09 13:23                   ` Kent Gibson
2019-10-09 13:30                 ` Drew Fustini
2019-10-09 14:11                   ` Kent Gibson
2019-10-09 15:50                     ` Bartosz Golaszewski
2019-10-09 16:19                       ` Kent Gibson
2019-10-09 23:59                   ` Kent Gibson
2019-10-10  7:47                     ` Drew Fustini
2019-10-10 10:14                       ` Kent Gibson
2019-10-10 11:17                         ` Kent Gibson
2019-10-11 13:04                           ` Drew Fustini
2019-10-11 13:06                         ` Drew Fustini
2019-10-11 13:49                           ` Kent Gibson
2019-10-09 11:32               ` Drew Fustini
2019-10-09 13:57       ` Drew Fustini
2019-10-09 14:01         ` Kent Gibson
2019-10-09 11:46   ` Drew Fustini

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