From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934144AbaFRIeL (ORCPT ); Wed, 18 Jun 2014 04:34:11 -0400 Received: from mx1.redhat.com ([209.132.183.28]:48500 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932108AbaFRIeH (ORCPT ); Wed, 18 Jun 2014 04:34:07 -0400 Message-ID: <53A14EB1.9090600@redhat.com> Date: Wed, 18 Jun 2014 10:32:49 +0200 From: Hans de Goede User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.6.0 MIME-Version: 1.0 To: linux-sunxi@googlegroups.com, Maxime Ripard CC: Samuel Ortiz , Lee Jones , Liam Girdwood , Mark Brown , Carlo Caione , Shuge , kevin@allwinnertech.com, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, devicetree@vger.kernel.org, linux-doc@vger.kernel.org, dev@linux-sunxi.org Subject: Re: [linux-sunxi] Re: [PATCH v4 4/7] regulator: axp20x: reset probe data before each probe References: <1402990723-28138-1-git-send-email-boris.brezillon@free-electrons.com> <1402990723-28138-5-git-send-email-boris.brezillon@free-electrons.com> <20140617204449.GD19730@lukather> <53A13BBF.7090202@free-electrons.com> In-Reply-To: <53A13BBF.7090202@free-electrons.com> X-Enigmail-Version: 1.6 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On 06/18/2014 09:11 AM, Boris BREZILLON wrote: > > On 17/06/2014 22:44, Maxime Ripard wrote: >> On Tue, Jun 17, 2014 at 09:38:40AM +0200, Boris BREZILLON wrote: >>> The init_data and of_node fields of the axp2xx_matches tables are filled >>> at each device probe by the axp20x_regulator_parse_dt function (which then >>> calls the of_regulator_match function). >>> This means we can probe a new device and consider data initialized during >>> the probe of another device as valid. >>> >>> Reset init_data and of_node field to NULL before each probe in order to >>> avoid this kind of issue. >>> >>> Signed-off-by: Boris BREZILLON >>> --- >>> drivers/regulator/axp20x-regulator.c | 9 +++++++++ >>> 1 file changed, 9 insertions(+) >>> >>> diff --git a/drivers/regulator/axp20x-regulator.c b/drivers/regulator/axp20x-regulator.c >>> index 7a30f49..d42bf6d 100644 >>> --- a/drivers/regulator/axp20x-regulator.c >>> +++ b/drivers/regulator/axp20x-regulator.c >>> @@ -324,6 +324,15 @@ static int axp20x_regulator_probe(struct platform_device *pdev) >>> nregulators = AXP20X_REG_ID_MAX; >>> } >>> >>> + /* >>> + * Reset matches table (this table might have been modified by a >>> + * previous AXP2xx device probe). >>> + */ >>> + for (i = 0; i < nmatches; i++) { >>> + matches[i].init_data = NULL; >>> + matches[i].of_node = NULL; >>> + } >>> + >> That looks rather hackish, especially since we've never been in such a >> case yet, since we have a single PMIC in our system. > > Even if something is unlikely to happen, it doesn't mean it's impossible. > I'm pretty sure there are (or will be) some systems containing several > identical PMICs in the wild, and fixing this possible bug now prevents > us (or other developers) from having a big headache debugging this in > the future. If you're really worried about this, you should also be worried about 2 probes running at the same time racing against each other (I know the bus level code will not do that now, but what about the future). If you cannot treat / use the global struct as const, then you really should have a local copy, and const-ify the global version and use it as a template to initialize the local copy. > BTW, what is hackish in this code ? See above, changing a global struct, and then re-initializing it on the next probe just is not pretty. TBH this raised my eyebrows the first time you posted it already, but I decided to let it be. But since we're discussing this now anyways I have to agree with Maxime. Regards, Hans