linux-kernel - unstable /sys interface from hmon

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Message-ID: <99aae36e-ddfd-dcd2-e544-9c28ae373959@cisco.com>
Date:   Mon, 30 Jan 2017 12:37:14 -0800
From:   Daniel Walker <danielwa@...co.com>
To:     "xe-kernel@...ernal.cisco.com" <xe-kernel@...ernal.cisco.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jean Delvare <khali@...ux-fr.org>,
        Guenter Roeck <linux@...ck-us.net>, lm-sensors@...sensors.org,
        linux-kernel@...r.kernel.org
Subject: 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