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[220.235.84.126]) by smtp.gmail.com with ESMTPSA id z4sm256436pfn.45.2019.10.08.17.22.14 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Tue, 08 Oct 2019 17:22:17 -0700 (PDT) Date: Wed, 9 Oct 2019 08:22:11 +0800 From: Kent Gibson To: Bartosz Golaszewski Cc: Drew Fustini , "open list:GPIO SUBSYSTEM" , Linus Walleij , Thomas Petazzoni Subject: Re: [RFC] gpio: expose pull-up/pull-down line flags to userspace Message-ID: <20191009002211.GA11168@sol> References: <20190921102522.8970-1-drew@pdp7.com> <20191008061512.GA19956@sol> <20191008232120.GA9225@sol> <20191008235626.GA10744@sol> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-gpio-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-gpio@vger.kernel.org On Wed, Oct 09, 2019 at 02:03:58AM +0200, Bartosz Golaszewski wrote: > śr., 9 paź 2019 o 01:56 Kent Gibson napisał(a): > > > > On Wed, Oct 09, 2019 at 01:30:18AM +0200, Bartosz Golaszewski wrote: > > > śr., 9 paź 2019 o 01:21 Kent Gibson napisał(a): > > > > > > > > On Tue, Oct 08, 2019 at 10:56:18PM +0200, Bartosz Golaszewski wrote: > > > > > wt., 8 paź 2019 o 08:15 Kent Gibson napisał(a): > > > > > > > > > > > > On Sat, Sep 21, 2019 at 12:25:23PM +0200, Drew Fustini wrote: > > > > > > > Add pull-up/pull-down flags to the gpio line get and > > > > > > > set ioctl() calls. Use cases include a push button > > > > > > > that does not have an external resistor. > > > > > > > > > > > > > > Addition use cases described by Limor Fried (ladyada) of > > > > > > > Adafruit in this PR for Adafruit_Blinka Python lib: > > > > > > > https://github.com/adafruit/Adafruit_Blinka/pull/59 > > > > > > > > > > > > > > Signed-off-by: Drew Fustini > > > > > > > --- > > > > > > > drivers/gpio/gpiolib.c | 12 ++++++++++++ > > > > > > > include/uapi/linux/gpio.h | 4 ++++ > > > > > > > 2 files changed, 16 insertions(+) > > > > > > > > > > > > > > diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c > > > > > > > index d9074191edef..9da1093cc7f5 100644 > > > > > > > --- a/drivers/gpio/gpiolib.c > > > > > > > +++ b/drivers/gpio/gpiolib.c > > > > > > > @@ -427,6 +427,8 @@ struct linehandle_state { > > > > > > > (GPIOHANDLE_REQUEST_INPUT | \ > > > > > > > GPIOHANDLE_REQUEST_OUTPUT | \ > > > > > > > GPIOHANDLE_REQUEST_ACTIVE_LOW | \ > > > > > > > + GPIOHANDLE_REQUEST_PULL_UP | \ > > > > > > > + GPIOHANDLE_REQUEST_PULL_DOWN | \ > > > > > > > GPIOHANDLE_REQUEST_OPEN_DRAIN | \ > > > > > > > GPIOHANDLE_REQUEST_OPEN_SOURCE) > > > > > > > > > > > > > > @@ -598,6 +600,10 @@ static int linehandle_create(struct gpio_device *gdev, void __user *ip) > > > > > > > set_bit(FLAG_OPEN_DRAIN, &desc->flags); > > > > > > > if (lflags & GPIOHANDLE_REQUEST_OPEN_SOURCE) > > > > > > > set_bit(FLAG_OPEN_SOURCE, &desc->flags); > > > > > > > + if (lflags & GPIOHANDLE_REQUEST_PULL_DOWN) > > > > > > > + set_bit(FLAG_PULL_DOWN, &desc->flags); > > > > > > > + if (lflags & GPIOHANDLE_REQUEST_PULL_UP) > > > > > > > + set_bit(FLAG_PULL_UP, &desc->flags); > > > > > > > > > > > > > > ret = gpiod_set_transitory(desc, false); > > > > > > > if (ret < 0) > > > > > > > @@ -1102,6 +1108,10 @@ static long gpio_ioctl(struct file *filp, unsigned int cmd, unsigned long arg) > > > > > > > if (test_bit(FLAG_OPEN_SOURCE, &desc->flags)) > > > > > > > lineinfo.flags |= (GPIOLINE_FLAG_OPEN_SOURCE | > > > > > > > GPIOLINE_FLAG_IS_OUT); > > > > > > > + if (test_bit(FLAG_PULL_DOWN, &desc->flags)) > > > > > > > + lineinfo.flags |= GPIOLINE_FLAG_PULL_DOWN; > > > > > > > + if (test_bit(FLAG_PULL_UP, &desc->flags)) > > > > > > > + lineinfo.flags |= GPIOLINE_FLAG_PULL_UP; > > > > > > > > > > > > > > if (copy_to_user(ip, &lineinfo, sizeof(lineinfo))) > > > > > > > return -EFAULT; > > > > > > > @@ -2475,6 +2485,8 @@ static bool gpiod_free_commit(struct gpio_desc *desc) > > > > > > > clear_bit(FLAG_REQUESTED, &desc->flags); > > > > > > > clear_bit(FLAG_OPEN_DRAIN, &desc->flags); > > > > > > > clear_bit(FLAG_OPEN_SOURCE, &desc->flags); > > > > > > > + clear_bit(FLAG_PULL_UP, &desc->flags); > > > > > > > + clear_bit(FLAG_PULL_DOWN, &desc->flags); > > > > > > > clear_bit(FLAG_IS_HOGGED, &desc->flags); > > > > > > > ret = true; > > > > > > > } > > > > > > > diff --git a/include/uapi/linux/gpio.h b/include/uapi/linux/gpio.h > > > > > > > index 4ebfe0ac6c5b..c2d1f7d908d6 100644 > > > > > > > --- a/include/uapi/linux/gpio.h > > > > > > > +++ b/include/uapi/linux/gpio.h > > > > > > > @@ -33,6 +33,8 @@ struct gpiochip_info { > > > > > > > #define GPIOLINE_FLAG_ACTIVE_LOW (1UL << 2) > > > > > > > #define GPIOLINE_FLAG_OPEN_DRAIN (1UL << 3) > > > > > > > #define GPIOLINE_FLAG_OPEN_SOURCE (1UL << 4) > > > > > > > +#define GPIOLINE_FLAG_PULL_UP (1UL << 5) > > > > > > > +#define GPIOLINE_FLAG_PULL_DOWN (1UL << 6) > > > > > > > > > > > > > > /** > > > > > > > * struct gpioline_info - Information about a certain GPIO line > > > > > > > @@ -62,6 +64,8 @@ struct gpioline_info { > > > > > > > #define GPIOHANDLE_REQUEST_ACTIVE_LOW (1UL << 2) > > > > > > > #define GPIOHANDLE_REQUEST_OPEN_DRAIN (1UL << 3) > > > > > > > #define GPIOHANDLE_REQUEST_OPEN_SOURCE (1UL << 4) > > > > > > > +#define GPIOHANDLE_REQUEST_PULL_UP (1UL << 5) > > > > > > > +#define GPIOHANDLE_REQUEST_PULL_DOWN (1UL << 6) > > > > > > > > > > > > > > /** > > > > > > > * struct gpiohandle_request - Information about a GPIO handle request > > > > > > > -- > > > > > > > 2.20.1 > > > > > > > > > > > > > Sorry for the late feedback, but I'm still not sure whether this patch > > > > > > is on track to be applied or not. I had thought not, at least not yet, > > > > > > but just in case... > > > > > > > > > > > > > > > > It still needs some fixes, but Linus seems to be fine with the general idea. > > > > > > > > > > > You have added the flags to linehandle_create, but not lineevent_create. > > > > > > Given that your primary use case is push buttons, isn't the event request > > > > > > at least as important as the handle request? Even ignoring your use > > > > > > case, I'd add them to lineevent_create just to maintain symmetry. > > > > > > > > > > > > Also, is it valid to set PULL_UP and PULL_DOWN simulaneously? > > > > > > I would think not, but I could be wrong. > > > > > > If not then that combination should be rejected with EINVAL. > > > > > > > > > > > > > > > > Yes, some validity checks of the flags must be added. I even did it in > > > > > my local branch[1]. > > > > > > > > > Your changes for linehandle_create look ok, but for lineevent_create > > > > you explicitly disabled PULL_UP and PULL_DOWN, and in a block labelled > > > > "This is just wrong: we don't look for events on output lines" at that. > > > > > > > > > > Yeah, feel free to change it. > > > > > Yeah, you see I didn't feel free to change it, as I thought the > > appropriate etiquette was to send comments to the original author. > > At least until the patch has been applied. > > Or are RFCs a special case? > > > > So either you review it and the author changes it and resends, or - if > for example you want to build on top of someone else's changes - you > take the patch, keep the original authorship, modify it and add your > signed-off-by tag with a small note on your changes in square > brackets. > Ok, but I'd still expect some feedback to the author to that effect. Maybe I missed it. > > > > > Re: direction and configuration changes on requested lines: I think > > > > > it's quite useful to add in the form of a new ioctl(): > > > > > GPIOHANDLE_SET_CONFIG_IOCTL or something. I started hacking on this > > > > > but eventually got more busy this week than I anticipated. I'm still > > > > > planning on sending an RFC by the end of the week though. > > > > > > > > > I have the reverse problem - bored and looking for something to do, so > > > > more than willing to help out - if you want it. > > > > > > > > > > Sure, in that case let's just wait for your patches. You can just > > > extend what I started, if you wish. > > > > > Yep, you sound tired. > > Are we talking about the SET_CONFIG here? If you have a link to what > > you've started I'll take a look, but as I've already said - I'm not > > about to go writing new ioctls without approval and guidance from you > > and Linus. If you have the ioctl defined I'm happy to take it from > > there. Well happy-ish. > > > > But there's absolutely nothing wrong with writing code even if you're > not sure about the solution - it's even encouraged[1]. It's much > easier to discuss existing code than potential solutions. > > [1] https://lkml.org/lkml/2000/8/25/132 > Exactly - show me your code. > > > > And while we're talking, does the gpio-mockup support pull up/down > > > > being set from the kernel side? > > > > > > > > > > No, but feel free to add it. > > > > > Ok, will have a look - cos I would like to add tests for the above and > > that will require the mockup supporting it as wel > > Do you also plan on extending libgpiod by any chance? > Well I thought that was your baby and was going to extend my Go library, and leave libgpiod to you. But I can help out with libgpiod as well. I suppose you'll want the Python and C++ bindings updated to match? Cheers, Kent.