unstable /sys interface from hmon

Hi,

Cisco recently upgraded to kernel 4.4.. We have applications which use the /sys interfaces for some hmon drivers. We found that the following patches,

https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=bab2243ce1897865e31ea6d59b0478391f51812b
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=c3b7cddc70075d525db6b3068d8b2b9158eedc84

Altered the interface as seen from userspace. These patches changed the paths in the following way,

Before,
/sys/bus/i2c/devices/14-0050/

After,
/sys/bus/i2c/devices/14-0050/hwmon/hwmon7

My impression was that /sys was suppose to be stable, and debugfs was unstable. I'm not sure what the current guidelines are for this, but we would request that hmon drivers maintain a stable interface from /sys. This change has cause upgrade issues for us which we would like to avoid in the future.

A patch to add in a compatibility layer would be welcome.

Daniel

Actually, the stable link to use would be /sys/class/hwmon/hwmon7 in both cases, and to check if the name attribute resides in hwmon7 or in hwmon7/device (which is the real change in your case - it moved from hwmon7/device to hwmon7, ie from the parent device to the hwmon device).

The key transition is the move from attaching the attributes to the parent device (here: the i2c device) to the hwmon device. libsensors handles this transition transparently; I assume you are not using it ?

A compatibility layer would have to link each attribute back to the parent device. Interesting idea, actually. I'll check if that is possible.

Thanks,
Guenter