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=-10.1 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable 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 2B07EC43460 for ; Tue, 27 Apr 2021 18:04:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 00E23613BD for ; Tue, 27 Apr 2021 18:03:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238488AbhD0SEm (ORCPT ); Tue, 27 Apr 2021 14:04:42 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46360 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236817AbhD0SEk (ORCPT ); Tue, 27 Apr 2021 14:04:40 -0400 Received: from pandora.armlinux.org.uk (pandora.armlinux.org.uk [IPv6:2001:4d48:ad52:32c8:5054:ff:fe00:142]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4A203C061574; Tue, 27 Apr 2021 11:03:56 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=armlinux.org.uk; s=pandora-2019; h=Sender:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=E7zb0oK3WjxUHxPQ/MvMrL1VfGxeoNA00qBLofYv7W8=; b=FrlrztJ1WNAkAfDrZuXxjpvtq PoOdbfxaFe4N5vi6/eA2wJPuQZNGs2b/oYKFHGtXcRDAO0wTPiaobXRSE8kIbZGGTRzubW9yGuYu4 p05trRy9CsroIfNM8Ig7D6abiqyr1uUMi8egibQpoIV8/Ogw0IHJEwfR5QoAwNH9frxpNKuwrH2aE MEwL2J7JQOLY2ITNGhWV8Jr5pGazh6tOLDJorVFu9Ap9atJuwK3vL5yO3VSJTYXPykF2lnYB4xLcG 5mSXlgZaG+WsJ5uSoBFwUoQdbGg5vLyTHAgR6pLb2e15pLSnF1gJL8c+rtxeBOGNWLFnPvJOIPhwB Ouc3pju9A==; Received: from shell.armlinux.org.uk ([fd8f:7570:feb6:1:5054:ff:fe00:4ec]:52796) by pandora.armlinux.org.uk with esmtpsa (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1lbS3v-0001pa-0i; Tue, 27 Apr 2021 19:03:55 +0100 Received: from linux by shell.armlinux.org.uk with local (Exim 4.92) (envelope-from ) id 1lbS3u-0004mx-Nj; Tue, 27 Apr 2021 19:03:54 +0100 Date: Tue, 27 Apr 2021 19:03:54 +0100 From: Russell King - ARM Linux admin To: Randy Dunlap Cc: linux-kernel@vger.kernel.org, linux-clk@vger.kernel.org Subject: Re: [PATCH] clk: : correct clk_get_parent() documentation Message-ID: <20210427180354.GV1463@shell.armlinux.org.uk> References: <20210427031342.5333-1-rdunlap@infradead.org> <20210427093809.GU1463@shell.armlinux.org.uk> <9574eefa-84ed-8674-f575-be47d2a51a1c@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <9574eefa-84ed-8674-f575-be47d2a51a1c@infradead.org> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: Russell King - ARM Linux admin Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Apr 27, 2021 at 10:07:04AM -0700, Randy Dunlap wrote: > On 4/27/21 2:38 AM, Russell King - ARM Linux admin wrote: > > On Mon, Apr 26, 2021 at 08:13:42PM -0700, Randy Dunlap wrote: > >> Make the kernel-doc return value agree with both the stub implementation > >> in and the non-stub function in drivers/clk/clk.c. > >> > >> Signed-off-by: Randy Dunlap > >> Cc: Russell King > >> Cc: linux-clk@vger.kernel.org > >> --- > >> There are several drivers that call clk_get_parent() and use its > >> return value as though it returns an ERR_PTR(). I am working on a > >> patch series to fix those. > > > > The whole premise of the CLK API is that: > > > > - clk values that IS_ERR() returns true are errors > > - clk values that IS_ERR() returns false are valid > > > > and that is that - nice, simple, easy to understand. So the > > documentation is correct. If clk_get_parent() needs to return an > > error, it does so by returning an error-pointer, not by returning > > NULL. > > Hm, so the 6 drivers that do this are OK then, if > clk_get_parent() returns NULL? > > > parent = clk_get_parent(clk); > if (IS_ERR(parent)) { > dev_err(cpu_dev, "Cannot get parent clock for CPU0\n"); > clk_put(clk); > return PTR_ERR(parent); > } > > /* Get parent CPU frequency */ > base_frequency = clk_get_rate(parent); > > boom? As I say, the premise is that only clocks where IS_ERR(clk) is true are an error. Everything else must be treated as an acceptable clock. Sometimes the NULL clock is used for "I don't have a clock", and that must not cause the API to go "boom". In the case of the CCF implementation, clk_get_rate(NULL) will return 0. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!