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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A3716EB64DD for ; Thu, 27 Jul 2023 22:11:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231161AbjG0WLO (ORCPT ); Thu, 27 Jul 2023 18:11:14 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39760 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229902AbjG0WLO (ORCPT ); Thu, 27 Jul 2023 18:11:14 -0400 Received: from mail-qt1-x833.google.com (mail-qt1-x833.google.com [IPv6:2607:f8b0:4864:20::833]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 571A6271E for ; Thu, 27 Jul 2023 15:11:13 -0700 (PDT) Received: by mail-qt1-x833.google.com with SMTP id d75a77b69052e-40398ccdaeeso8072721cf.3 for ; Thu, 27 Jul 2023 15:11:13 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20221208; t=1690495872; x=1691100672; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:from:to:cc:subject:date :message-id:reply-to; bh=tEh7JReNRZOP+ZRbj/0ebr1DojcV2uFwlOYTP1QsgQ0=; b=oefp9HHuDc+4ygSk83D2X0OL0jdkqWfzW2c9ldsTl1SysCOo5A8U58PIgBY8RDEskz KW9HOzQ/c6uqb+jSXqemjeHDz11oCA3SArc6wHzT9wp1FGX2hXze6aWxKfGihuzaJ0vr JMp8tcOznYTfl7TKCT//I/KGWsmexNVL442HLY4hR+yOcPhc9XAyFiMnW/IuuGNBFGcx tGPjBBo+2aKSeo3ClwO+59oRYiOAkFqvsB1Haxlvt3Et/ZWkxfKJZBlWFJlomd+Nv7ns w9XcSSPMa8Dyh9IytQcPzq6oMWhV3xYgtIS1AXnlqSIu7F8dEAe5qLSf6zvuIWOjBWDs DJ4w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1690495872; x=1691100672; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=tEh7JReNRZOP+ZRbj/0ebr1DojcV2uFwlOYTP1QsgQ0=; b=cpgY6qLVIdX+HsmBCjI4ayC5qDm2pPmUlm6jOpUh6yHIGNPvK+emEgaqADFLEu7pZ5 AXDmgcTpJU6EpyxdkEeq/3TKzY8PCdr1ZKB/+90XMpyGYzQ/0Ft7jri2eN8aaA0xn2Mk VvVTyMlzqJjQWqqDB2VVG7jtWLbzHuAD2n0NwFxlHjamRHGuQHA/7una95NFL5sumeKR S9EXomZj3QCiMddN3cBJ1pQLKPfIKQSAfDiT6cALP/4BCzY0IydTadkEcnYIk5sQ+wTA GZlTYMhxpqAnS4phkoftXUbW+VFRUlhnufbx2/THXo+Gx6fnAQ67niczd/EQabXPS3ZQ UsxQ== X-Gm-Message-State: ABy/qLbiGxLClf5snZ0Br+jjaiHjrYU/gP8Xprinkudk4XAE0AF2IdVc b0/Jd2beF8Xtxy6UfeEJSAUu+9l4KtytlWm13nTOufOjq/Y= X-Google-Smtp-Source: APBJJlEl1jTZAcZjAEbR/l5t14wmDwcR/n/jhVmZRuFxeCeNwTaJOGfRihSqR/SIVRKxLRdU7GSkjBDkyVKr4wtvcQw= X-Received: by 2002:ac8:5915:0:b0:400:aaaf:cf0b with SMTP id 21-20020ac85915000000b00400aaafcf0bmr1057039qty.4.1690495872435; Thu, 27 Jul 2023 15:11:12 -0700 (PDT) MIME-Version: 1.0 References: In-Reply-To: From: andy pugh Date: Thu, 27 Jul 2023 23:10:36 +0100 Message-ID: Subject: Re: [libgpiod] gpiod_line_get_value_bulk may be broken? To: Kent Gibson Cc: linux-gpio@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-gpio@vger.kernel.org On Thu, 27 Jul 2023 at 22:55, Kent Gibson wrote: > On a Pi is it significantly faster to go direct to hardware using > /dev/gpiomem, rather than going via the kernel as libgpiod does. > I do my best to avoid using gpiomem these days, but if you really need to > minimize CPU cycles or latency then that is another option. The existing driver uses gpiomem, but the interface used seems to not be set up in Debian Bookworm. It might be available in _Raspbian_ but that current Raspbian version is based on Bullseye (or Buster) https://github.com/LinuxCNC/linuxcnc/issues/2371 Is where the suggestion was made to try gpiod, initially because of a problem with the way we were detecting Pi versions, but then because gpiomem wasn't there. (It can probably be configured, but we have a user base largely made of machinists, not Linux enthusiasts) --=20 atp "A motorcycle is a bicycle with a pandemonium attachment and is designed for the especial use of mechanical geniuses, daredevils and lunatics." =E2=80=94 George Fitch, Atlanta Constitution Newspaper, 1912