From patchwork Fri Oct 11 19:15:20 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Saravana Kannan X-Patchwork-Id: 11186249 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id BEB2176 for ; Fri, 11 Oct 2019 19:15:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9ED7D21D71 for ; Fri, 11 Oct 2019 19:15:38 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="SjWuOTsG" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728981AbfJKTPe (ORCPT ); Fri, 11 Oct 2019 15:15:34 -0400 Received: from mail-pf1-f201.google.com ([209.85.210.201]:39363 "EHLO mail-pf1-f201.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728851AbfJKTPd (ORCPT ); Fri, 11 Oct 2019 15:15:33 -0400 Received: by mail-pf1-f201.google.com with SMTP id b13so8216413pfp.6 for ; Fri, 11 Oct 2019 12:15:32 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=wwUIXG8zaTQahpGiWbKYxnh72iiHnCVZCniLVYgkymY=; b=SjWuOTsGX96zO37k1lrS0YGrpMuH9atVN00vNP8ziHSqCn5t4dh1R8CJorCFIjPdkg WEWKUOZPjx8vnNqtI6YQDXKsRyBAVvql3hBRri2FhH+wJ0084Fb4JXe0niwBFfhvnYmx PRw9piDFj/NQVRK8uguTgpNyFy1hd0f2bGlygLYPWJqEI/bfEIsGC7vIwGn4XrC154Cf CFNI4CQ1F5Bg649N5plNnllxLyf1xvpsBPAYffUiDd8QbDT+JZf0MTjcec0yP+Yh1ELW n845mj7mpnjt67qWFGOA8qyslxjBTS35v/vcpCBs0h0+KtkSBPxWDP/L07tiwi84Xc/Z 2r0A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=wwUIXG8zaTQahpGiWbKYxnh72iiHnCVZCniLVYgkymY=; b=bfBTF6q4dgVdWczqPp47/sj4Qi8eSENwHJFSD46hGNunLAExpHDrXG9pT+GSx+tLaQ UmhGn6seRRd4i9xIwzk1WP/8YFTWdq0YmD8GjxBAxl3tYlH3qg2ntkOMVnwUjChqj+jA rD1TbiK4vwPix1Q2Oh7yvcgQsqKQqYFcOY38otqXoK0vaavifg+RINyexMIKFaeO9cYZ u+2bBJC1zH8bR31LR2dByXq0r/CwAh1egErrpKT1vqWG2f3O2eYtKJd7D5VzoylHbGG7 Uaxb+H4T9SWjhw32w0/2laYigb6sAomePOzIpYGDUmXop3U2pPNXKQWeomwDOaxcLNLp i6PA== X-Gm-Message-State: APjAAAVDqYSbIQ5NXtWiKfG5n8AFOcxYUI4XcMnutW1+TnJjBvxTc+GM afARpP5a98DsTY0/0P6xvKze0YYFtOs9zME= X-Google-Smtp-Source: APXvYqzaCgjn0N9hABwlUZ7A/oUwETCiJvUmLoZt+RlNeEME8ZHLP4663B/JrOTQqolBHH7K1mL5F5e9EcUtEu0= X-Received: by 2002:a63:6a46:: with SMTP id f67mr17738001pgc.87.1570821332209; Fri, 11 Oct 2019 12:15:32 -0700 (PDT) Date: Fri, 11 Oct 2019 12:15:20 -0700 In-Reply-To: <20191011191521.179614-1-saravanak@google.com> Message-Id: <20191011191521.179614-3-saravanak@google.com> Mime-Version: 1.0 References: <20191011191521.179614-1-saravanak@google.com> X-Mailer: git-send-email 2.23.0.700.g56cf767bdb-goog Subject: [PATCH v1 2/3] driver: core: Improve documentation for fwnode_operations.add_links() From: Saravana Kannan To: Jonathan Corbet , Rob Herring , Frank Rowand , "Rafael J. Wysocki" , Len Brown , Greg Kroah-Hartman Cc: Saravana Kannan , Stephen Boyd , kernel-team@android.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, devicetree@vger.kernel.org, linux-acpi@vger.kernel.org Sender: linux-acpi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-acpi@vger.kernel.org The add_links() ops shouldn't return on the first failed device link add. It needs to continue trying to add device links to other suppliers that are available. The documentation didn't explain WHY this behavior is necessary. So, update the documentation with an example that explains why this is necessary. Signed-off-by: Saravana Kannan --- include/linux/fwnode.h | 21 +++++++++++++++++++-- 1 file changed, 19 insertions(+), 2 deletions(-) diff --git a/include/linux/fwnode.h b/include/linux/fwnode.h index 6ae05b9ce359..97223e2410bd 100644 --- a/include/linux/fwnode.h +++ b/include/linux/fwnode.h @@ -71,8 +71,25 @@ struct fwnode_reference_args { * links to all the suppliers of the device that are available at * the time this function is called. The function must NOT stop * at the first failed device link if other unlinked supplier - * devices are present in the system. If some suppliers are not - * yet available, this function will be called again when other + * devices are present in the system. This is necessary for the + * driver/bus sync_state() callbacks to work correctly. + * + * For example, say Device-C depends on suppliers Device-S1 and + * Device-S2 and the dependency is listed in that order in the + * firmware. Say, S1 gets populated from the firmware after + * late_initcall_sync(). Say S2 is populated and probed way + * before that in device_initcall(). When C is populated, if this + * add_links() function doesn't continue past a "failed linking to + * S1" and continue linking C to S2, then S2 will get a + * sync_state() callback before C is probed. This is because from + * the perspective of S2, C was never a consumer when its + * sync_state() evaluation is done. To avoid this, the add_links() + * function has to go through all available suppliers of the + * device (that corresponds to this fwnode) and link to them + * before returning. + * + * If some suppliers are not yet available (indicated by an error + * return value), this function will be called again when other * devices are added to allow creating device links to any newly * available suppliers. *