From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752166AbbASQoq (ORCPT ); Mon, 19 Jan 2015 11:44:46 -0500 Received: from mga11.intel.com ([192.55.52.93]:28778 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751520AbbASQoo (ORCPT ); Mon, 19 Jan 2015 11:44:44 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.97,862,1389772800"; d="scan'208";a="442322225" From: "Pandruvada, Srinivas" To: "Baluta, Daniel" CC: "lars@metafoo.de" , "linux-kernel@vger.kernel.org" , "knaack.h@gmx.de" , "jic23@kernel.org" , "Purdila, Octavian" , "linux-iio@vger.kernel.org" , "Westerberg, Mika" , "pmeerw@pmeerw.net" , "beomho.seo@samsung.com" , "gwendal@chromium.org" Subject: Re: [RFC PATCH] iio: ak8975: Make sure chipset is always initialized Thread-Topic: [RFC PATCH] iio: ak8975: Make sure chipset is always initialized Thread-Index: AQHQHJv/pV0/XzoQpUK45pIcNb1+QJzIOKwAgAAiaIA= Date: Mon, 19 Jan 2015 16:44:31 +0000 Message-ID: <1421685827.4459.397.camel@spandruv-desktop.jf.intel.com> References: <1418923002-901-1-git-send-email-daniel.baluta@intel.com> <5494A3D6.60607@gmx.de> <1419110796.2843.6.camel@spandruv-hsb-test> <1419110952.2843.8.camel@spandruv-hsb-test> In-Reply-To: Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.7.199.150] Content-Type: text/plain; charset="utf-8" Content-ID: <6216D29E7E51AA4E82131928876AC75C@intel.com> MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from base64 to 8bit by nfs id t0JGipqj004754 On Mon, 2015-01-19 at 16:40 +0200, Daniel Baluta wrote: > Hello, > > On Sat, Dec 20, 2014 at 11:29 PM, Pandruvada, Srinivas > wrote: > > +Mika > > > > On Sat, 2014-12-20 at 13:26 -0800, Srinivas Pandruvada wrote: > >> On Sat, 2014-12-20 at 00:25 +0200, Daniel Baluta wrote: > >> > On Sat, Dec 20, 2014 at 12:16 AM, Hartmut Knaack wrote: > >> > > Daniel Baluta schrieb am 18.12.2014 um 18:16: > >> > >> When using ACPI, if acpi_match_device fails then chipset enum will be > >> > >> uninitialized and &ak_def_array[chipset] will point to some bad address. > >> > >> > >> I am missing something. You are enumerated over i2c device, which was > >> created from ACPI PNP resource. There is a valid handle or and the > >> device has an ACPI companion at the least. If this failing, I have to > >> check the code for acpi i2c. > >> Can you check why this check failed? We may have bug in i2c handling. > > You are right about this. Under normal circumstances, if probe is called > then acpi_match_device will not fail. I even tried to remove the > device after probe > but before acpi_match_device, anyhow acpi_match_device was still successful :) > > This is more a matter of code correctness. > > In ak8975_match_acpi_device we have: > > » const struct acpi_device_id *id; > > » id = acpi_match_device(dev->driver->acpi_match_table, dev); > » if (!id) > » » return NULL; > » *chipset = (int)id->driver_data; > > Compiler complains on the fact that chipset might be uninitialized > if this returns NULL, and we shouldn't ignore this warning even this case > will never happen. > Will this fix? data->chipset = AK8975; before ak8975_match_acpi_device(&client->dev, &data->chipset); Thanks, Srinivas > We could use some code injection techniques to force acpi_match_device > to return NULL tough. > > >> > >> This fixes the following compilation warning: > >> > >> > >> > >> drivers/iio/magnetometer/ak8975.c: In function ‘ak8975_probe’: > >> > >> drivers/iio/magnetometer/ak8975.c:788:14: warning: ‘chipset’ may be used > >> > >> uninitialized in this function [-Wmaybe-uninitialized] > >> > >> data->def =ak_def_array[chipset]; > >> > >> > >> > >> Reported-by: Octavian Purdila > >> > >> Signed-off-by: Daniel Baluta > >> > >> --- > >> > >> This is a RFC because while I'm pretty sure that chipset should be initialized > >> > >> with AK_MAX_TYPE in ak8975_match_acpi_device, I am not sure if we can live with > >> > >> a NULL return value of ak8975_match_acpi_device. Current implementation ignores > >> > >> return value of ak8975_match_acpi_device. > >> > > This seems to be the actual problem: these _match_acpi_device functions return > >> > > NULL on failure, and this should be checked for. > >> > > >> > Ok, so this would acceptable? > >> > > >> > diff --git a/drivers/iio/magnetometer/ak8975.c > >> > b/drivers/iio/magnetometer/ak8975.c > >> > index 0d10a4b..68d99e9 100644 > >> > --- a/drivers/iio/magnetometer/ak8975.c > >> > +++ b/drivers/iio/magnetometer/ak8975.c > >> > @@ -776,8 +776,9 @@ static int ak8975_probe(struct i2c_client *client, > >> > name = id->name; > >> > } else if (ACPI_HANDLE(&client->dev)) > >> > name = ak8975_match_acpi_device(&client->dev, &chipset); > >> > - else > >> > - return -ENOSYS; > >> > + > >> > + if (!name) > >> > + return -ENODEV; > >> > > >> > > >> > I still have some doubts about return code in case of error. > >> > > >> > For ak8975 we use -ENOSYS, but for kxcjk-1013 we use -ENODEV. > >> > > >> > I will send a patch after we clear this out. > >> > > >> > thanks, > >> > Daniel. > >> > > {.n++%ݶw{.n+{G{ayʇڙ,jfhz_(階ݢj"mG?&~iOzv^m ?I