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=-1.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED autolearn=no 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 5380AC433DF for ; Sat, 27 Jun 2020 16:59:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2286E206C0 for ; Sat, 27 Jun 2020 16:59:01 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=walle.cc header.i=@walle.cc header.b="KDjyolna" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725900AbgF0Q7A (ORCPT ); Sat, 27 Jun 2020 12:59:00 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60820 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725882AbgF0Q7A (ORCPT ); Sat, 27 Jun 2020 12:59:00 -0400 Received: from ssl.serverraum.org (ssl.serverraum.org [IPv6:2a01:4f8:151:8464::1:2]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 17702C061794; Sat, 27 Jun 2020 09:59:00 -0700 (PDT) Received: from ssl.serverraum.org (web.serverraum.org [172.16.0.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ssl.serverraum.org (Postfix) with ESMTPSA id 9486622708; Sat, 27 Jun 2020 18:58:54 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=walle.cc; s=mail2016061301; t=1593277134; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=1nGL+tnFIAt0ZoojBnWf47XaRiyJlS+iVijOfL+WgN8=; b=KDjyolnahGMCwSPrN3p3Fo+EAzc4V2j/Qj1pS0mkzPzRQ7FFlvsijQDE8mL1WhFn6ZT6Sm +s0a+4agmyvkqpNPN410Cod0aFiiGM8WmlQmpsVTQD1HqjFTBDoxk9otowPmCIj/fVADf8 u4Sf253hGdU+Hqycn2N/c4J/2tX2OwQ= MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Date: Sat, 27 Jun 2020 18:58:54 +0200 From: Michael Walle To: Andy Shevchenko Cc: Sungbo Eo , Linus Walleij , Bartosz Golaszewski , Linux Kernel Mailing List , "open list:GPIO SUBSYSTEM" Subject: Re: [PATCH] gpio: add GPO driver for PCA9570 In-Reply-To: References: <20200623060526.29922-1-mans0n@gorani.run> <80bbca9a625b2a0feb9b816906549b7c@walle.cc> <2291c01d-30df-518e-a952-644bd955f1f3@gorani.run> <69f5d1a1970838b8c4bd8d6e8dba6cac@walle.cc> <9956439a3c887dde7b2b8fa48de20db2@walle.cc> User-Agent: Roundcube Webmail/1.4.5 Message-ID: <83f1fba7fb04780b84c5e96a184f61f9@walle.cc> X-Sender: michael@walle.cc Sender: linux-gpio-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-gpio@vger.kernel.org Hi, Am 2020-06-24 16:52, schrieb Andy Shevchenko: > On Wed, Jun 24, 2020 at 4:46 PM Michael Walle wrote: [..] >> So you just write one byte of data (or you might repeat it, but >> that is just as if you start a new i2c transaction, just that >> you save the i2c addressing). > > You can write the same value twice. > It means that the first byte can represent the register address. But > it's still too volatile. In this case the output pin will hold the value of the "fake" address register for a short period of time. No? > Perhaps regmap can gain something like register-less communication. I don't know if that is worth it (and if that is an intended use of regmap). -michael