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=-8.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,USER_AGENT_MUTT autolearn=ham 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 4E98BECDE4B for ; Thu, 8 Nov 2018 19:25:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1C30A204FD for ; Thu, 8 Nov 2018 19:25:15 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1C30A204FD Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727029AbeKIFCG (ORCPT ); Fri, 9 Nov 2018 00:02:06 -0500 Received: from mga17.intel.com ([192.55.52.151]:47536 "EHLO mga17.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725723AbeKIFCG (ORCPT ); Fri, 9 Nov 2018 00:02:06 -0500 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from orsmga001.jf.intel.com ([10.7.209.18]) by fmsmga107.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 08 Nov 2018 11:25:13 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.54,480,1534834800"; d="scan'208";a="106610765" Received: from smile.fi.intel.com (HELO smile) ([10.237.72.86]) by orsmga001.jf.intel.com with ESMTP; 08 Nov 2018 11:25:10 -0800 Received: from andy by smile with local (Exim 4.91) (envelope-from ) id 1gKpvR-0008RB-Pn; Thu, 08 Nov 2018 21:25:09 +0200 Date: Thu, 8 Nov 2018 21:25:09 +0200 From: Andy Shevchenko To: Rob Herring Cc: Heikki Krogerus , "Rafael J. Wysocki" , Mika Westerberg , "linux-kernel@vger.kernel.org" , linux-acpi@vger.kernel.org, devicetree@vger.kernel.org Subject: Re: [PATCH v2 3/4] of/property: Add of_fwnode_name() Message-ID: <20181108192509.GW10650@smile.fi.intel.com> References: <20181108165156.60073-1-heikki.krogerus@linux.intel.com> <20181108165156.60073-4-heikki.krogerus@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Nov 08, 2018 at 12:23:51PM -0600, Rob Herring wrote: > On Thu, Nov 8, 2018 at 10:52 AM Heikki Krogerus > wrote: > > > > This implements get_name fwnode op for DT. > > > > Signed-off-by: Heikki Krogerus > > --- > > drivers/of/property.c | 11 +++++++++++ > > 1 file changed, 11 insertions(+) > > > > diff --git a/drivers/of/property.c b/drivers/of/property.c > > index f46828e3b082..9bc8fe136fa3 100644 > > --- a/drivers/of/property.c > > +++ b/drivers/of/property.c > > @@ -823,6 +823,16 @@ static void of_fwnode_put(struct fwnode_handle *fwnode) > > of_node_put(to_of_node(fwnode)); > > } > > > > +static int of_fwnode_get_name(const struct fwnode_handle *fwnode, char *buf) > > +{ > > + const char *name = kbasename(to_of_node(fwnode)->full_name); > > + size_t len = strchrnul(name, '@') - name; > > + > > + snprintf(buf, len + 1, "%s", name); > > This can be simplified to: > > snprintf(..., "%pOFn", to_of_node(fwnode)) > > But that presents a problem with knowing the length. Not passing in > the buf length is not good design because you can't tell if you > overflow the buffer. Either you can pass in the length of buf or do > the allocation here. In the latter case, then you can use kasnprintf. > The downside to doing the allocation here is then get_name() has side > effect of allocating memory that the caller needs to be aware of. Agree on matter of potential overflow. I wouldn't limit users with 32 characters for node name if it's not by both ACPI and DT specifications. OTOH allocating and freeing memory in a loop each time when we would like to go through the child nodes sounds much worse scenario to me. Thus, giving a length of the buffer is a good enough compromise. > However, I think the current API is better. It leaves low-level > details up to the firmware implementation. But as long as .get_name() > is not exposed to drivers I don't really care that much. I don't think this concept is changed by Heikki's patch series. It provides a common abstract function on top of more low-level firmware implementation which I consider a good approach. -- With Best Regards, Andy Shevchenko