From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hans de Goede Subject: Re: Re: [PATCH v4 4/7] regulator: axp20x: reset probe data before each probe Date: Wed, 18 Jun 2014 10:32:49 +0200 Message-ID: <53A14EB1.9090600@redhat.com> 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> Reply-To: linux-sunxi-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Return-path: In-Reply-To: <53A13BBF.7090202-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org> List-Post: , List-Help: , List-Archive: Sender: linux-sunxi-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org List-Subscribe: , List-Unsubscribe: , To: linux-sunxi-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org, Maxime Ripard Cc: Samuel Ortiz , Lee Jones , Liam Girdwood , Mark Brown , Carlo Caione , Shuge , kevin-0TFLnhJekD6UEPyfVivIlAC/G2K4zDHf@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-doc-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, dev-3kdeTeqwOZ9EV1b7eY7vFQ@public.gmane.org List-Id: devicetree@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