From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Return-path: Date: Tue, 27 Jun 2017 13:23:00 +0100 From: Sudip Mukherjee To: Guenter Roeck Cc: Jean Delvare , linux-kernel@vger.kernel.org, Fenghua Yu , linux-hwmon@vger.kernel.org Subject: Re: userspace regression with hwmon Message-ID: <20170627122300.GA14227@sudip-tp> References: <20170626143320.GA1976@sudip-tp> <20170626170611.GC20491@roeck-us.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170626170611.GC20491@roeck-us.net> List-ID: On Mon, Jun 26, 2017 at 10:06:11AM -0700, Guenter Roeck wrote: > On Mon, Jun 26, 2017 at 03:33:20PM +0100, Sudip Mukherjee wrote: > > Hi Guenter, Jean, > > > > The patch d72d19c26c41 ("hwmon: (coretemp) Convert to use > > devm_hwmon_device_register_with_groups") has changed the location of the > > sysfs nodes from /sys/devices/platform/coretemp.0/ to > > /sys/devices/platform/coretemp.0/hwmon/hwmon0/ and that has broken > > some of our usespace applications when we have updated the kernel from > > v3.8 to v4.4. For now I am reverting that said patch in our production > > kernel (based on v4.4) but that is not an elegant solution. > > Do you have any other reports like this? I am sure changing the paths > > upstream will now break some other userspace. So, what can be an elegant > > solution to our problem? or do we always need to carry an out-of-tree > > patch for our production kernel? > > > > The problem only occurs if attributes are accessed using the raw path, > and if user space does not take into account that attributes may reside > in the hwmon directory (/sys/class/hwmon/hwmonX) _or_ in the device > directory (/sys/class/hwmon/hwmonX/device). There is no guarantee that > the raw path doesn't change from release to release; that is what the > symlinks are for. Actually, I have seen the raw platform device path > change over time, so I am surprised that this never affected you. Well, using the raw platform device path was a bad design decision. But I still see a difference. In v3.8 all the temp* nodes were in /sys/class/hwmon/hwmon0/device/ but in v4.4 I can see that they are in /sys/class/hwmon/hwmon0/. So if we do modify the code, then we still need to have two versions of userspace code based on the kernel. -- Regards Sudip