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=-12.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, MAILING_LIST_MULTI,NICE_REPLY_A,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 EB73BC433B4 for ; Tue, 27 Apr 2021 18:11:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C4565613EA for ; Tue, 27 Apr 2021 18:11:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236882AbhD0SLz (ORCPT ); Tue, 27 Apr 2021 14:11:55 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47926 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235505AbhD0SLu (ORCPT ); Tue, 27 Apr 2021 14:11:50 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 70E28C061574; Tue, 27 Apr 2021 11:11:05 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=Content-Transfer-Encoding:Content-Type: In-Reply-To:MIME-Version:Date:Message-ID:From:References:Cc:To:Subject:Sender :Reply-To:Content-ID:Content-Description; bh=iSFwWZDgq06eV2j6xMstjt+tfTQP9r/fGWLHY8KCDgY=; b=E14V1iHnWizv6jQBIpVNVsFFsN 4CZUnf+NhNCPUfoXYjeIZdOaU+TE5uXPsadfYDIeSNnzXU7g5h99a5EXpDC/sn+9JfHgFmbZ9ceAk wr22TnxplBhdNIi1uSzoWyfZ6v8WJEt6+MInzDIEJO7Dea4geNCeAbrl1XlG/Hfu/9pkf6219v4vr ieTWDaz/+urBCeW9HVi5AyuIkLtTGfn2mlCEU7+dlNMaw1dREgLwxsmSVDJmtJF8WVsm2phaksArm bMlQcq0Xjv9jeSKyj9wn1feWjhi0rLjIBZS3u2C0StdtqkBHgO3OhEYPqa634Kkz3fTUon32n0sD7 LW+KBd6g==; Received: from [2601:1c0:6280:3f0::df68] by casper.infradead.org with esmtpsa (Exim 4.94 #2 (Red Hat Linux)) id 1lbSAX-007ElB-4f; Tue, 27 Apr 2021 18:10:48 +0000 Subject: Re: [PATCH] clk: : correct clk_get_parent() documentation To: Russell King - ARM Linux admin Cc: linux-kernel@vger.kernel.org, linux-clk@vger.kernel.org References: <20210427031342.5333-1-rdunlap@infradead.org> <20210427093809.GU1463@shell.armlinux.org.uk> <9574eefa-84ed-8674-f575-be47d2a51a1c@infradead.org> <20210427180354.GV1463@shell.armlinux.org.uk> From: Randy Dunlap Message-ID: <5db90f0d-a272-3f7b-ed9e-c025c14c00fd@infradead.org> Date: Tue, 27 Apr 2021 11:10:42 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.0 MIME-Version: 1.0 In-Reply-To: <20210427180354.GV1463@shell.armlinux.org.uk> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 4/27/21 11:03 AM, Russell King - ARM Linux admin wrote: > 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. > Thank you for the clarification. That is helpful. -- ~Randy