From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-11.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 150A7C3A5A6 for ; Mon, 23 Sep 2019 08:38:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DA8262064A for ; Mon, 23 Sep 2019 08:38:56 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=bgdev-pl.20150623.gappssmtp.com header.i=@bgdev-pl.20150623.gappssmtp.com header.b="GSDf8XcZ" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729376AbfIWIi4 (ORCPT ); Mon, 23 Sep 2019 04:38:56 -0400 Received: from mail-io1-f65.google.com ([209.85.166.65]:41334 "EHLO mail-io1-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729373AbfIWIi4 (ORCPT ); Mon, 23 Sep 2019 04:38:56 -0400 Received: by mail-io1-f65.google.com with SMTP id r26so31355805ioh.8 for ; Mon, 23 Sep 2019 01:38:55 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bgdev-pl.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc:content-transfer-encoding; bh=Z66RdQZHaR+LFy+7u3wSKlBb2kvT7TR/msSi0TmhaO8=; b=GSDf8XcZcj/M0eCtxhIR1y0CuHqRDf8/vYNi6vC6QDKqw2umXbrQTytViDT5lcn1K1 f2uQeQ96ORPwLevtzwj6iEyQSk58O8ESuhUs3fiQKEhSqYBwWR6niVbH8mjV2uvJSIJf OHRsxS8elhcUkT8Kg98Egcr+VTMd+8FPjpLfhT2FjKurSJiOZURPB0Ens+U8PAPpTljq Cw/zyJF49blxSLuUKsmzrhTEEg8ICbS3eIRGx/8DmaLmOro1bRXxRd+1c2AzEAyG7UAB cvGiEGOXEPek61X8ylRgfBGtUla6Dwlofgl8MiV+k5CP3WXpAaBlZL9AxDRca0CFSYYB 63TA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc:content-transfer-encoding; bh=Z66RdQZHaR+LFy+7u3wSKlBb2kvT7TR/msSi0TmhaO8=; b=mxV/LRC4SNfR8/72kaiIr7wkIyZqwNZE2plq0KeuxfzOyO99oulVVMcElKHI8hpA9q rUIQcxLRIi6BWOl7wEgSAhZZw7MxHjwl59Nj85r9yisUIaObVMUmIkstNrd/n7jhYYSz xrWzl0q6lv7rbvQhrXZoYn3FVzKto03aerPlo9HkZKnpNl8nc9iRQXHTwN3Oebdl8TKG Zrv2g+PywL2kMZBahLEigOlH6tF3wcAR0SUATsh+0SwHk3pzzYRAenpkfSQMiK/1qAAs EXZr98yWKkf96YjuvVPFatfP91+EgYcs4yux2/hdpbT1IgK7XbAIwiepuxbjfThwuQQL leYw== X-Gm-Message-State: APjAAAWLV50vP9HnVBwIplLOo6gce6FaCCno0JfXL8PkJXBaS9vc80BA lMUwPvBYCCfOFwC2ZaBxN3MqQm4qhmFTjyI+x0uo3w== X-Google-Smtp-Source: APXvYqwommw18/whlR1YCZCLlPve/5YQoTF9NQaaC3N+EQmJx3oAfamEJfaE1y1bv0X2KE/IbHs7nousAls/iRtZYQg= X-Received: by 2002:a05:6638:5ba:: with SMTP id b26mr32886006jar.57.1569227934765; Mon, 23 Sep 2019 01:38:54 -0700 (PDT) MIME-Version: 1.0 References: <20190921102522.8970-1-drew@pdp7.com> In-Reply-To: <20190921102522.8970-1-drew@pdp7.com> From: Bartosz Golaszewski Date: Mon, 23 Sep 2019 10:38:44 +0200 Message-ID: Subject: Re: [RFC] gpio: expose pull-up/pull-down line flags to userspace To: Drew Fustini Cc: "open list:GPIO SUBSYSTEM" , Linus Walleij , Thomas Petazzoni Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Sender: linux-gpio-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-gpio@vger.kernel.org sob., 21 wrz 2019 o 12:27 Drew Fustini napisa=C5=82(a): > > 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 *gde= v, 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 =3D 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 |=3D (GPIOLINE_FLAG_OPEN_SOURCE | > GPIOLINE_FLAG_IS_OUT); > + if (test_bit(FLAG_PULL_DOWN, &desc->flags)) > + lineinfo.flags |=3D GPIOLINE_FLAG_PULL_DOWN; > + if (test_bit(FLAG_PULL_UP, &desc->flags)) > + lineinfo.flags |=3D 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 *des= c) > 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 =3D 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 > Hi Drew, I remember discussing it with Linus some time ago. This may not be as straightforward as simply adding new flags. Since PULL-UP/DOWN resistors can - among other parameters - also have configurable resistance, we'll probably need some kind of a structure for this ioctl() to pass any additional information to the kernel. Since we can't change ABI this may require adding a whole new ioctl() for extended configuration. This in turn has to be as future-proof as possible - if someone asks for user-space-configurable drive-strength, the new ioctl() should be ready for it. I should have some bandwidth in the coming days, so I'll try to give it a t= ry. Bart