X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=Documentation%2Fsysfs-rules.txt;h=ce60ffa94d2d709681ed339fc4ef25369a2c377d;hb=43bd40e5b6eab989a2186b09d45b8ff8efd127b2;hp=a5f985ee1822fe37497d09c08a75acf599cba887;hpb=861e66d3418a90f57b31a50110fc70b23569c551;p=firefly-linux-kernel-4.4.55.git

diff --git a/Documentation/sysfs-rules.txt b/Documentation/sysfs-rules.txt
index a5f985ee1822..ce60ffa94d2d 100644
--- a/Documentation/sysfs-rules.txt
+++ b/Documentation/sysfs-rules.txt
@@ -161,3 +161,24 @@ versions of the sysfs interface.
   the device that matches the expected subsystem. Depending on a specific
   position of a parent device or exposing relative paths using "../" to
   access the chain of parents is a bug in the application.
+
+- When reading and writing sysfs device attribute files, avoid dependency
+  on specific error codes wherever possible. This minimizes coupling to
+  the error handling implementation within the kernel.
+
+  In general, failures to read or write sysfs device attributes shall
+  propagate errors wherever possible. Common errors include, but are not
+  limited to:
+
+  -EIO: The read or store operation is not supported, typically returned by
+        the sysfs system itself if the read or store pointer is NULL.
+
+  -ENXIO: The read or store operation failed
+
+  Error codes will not be changed without good reason, and should a change
+  to error codes result in user-space breakage, it will be fixed, or the
+  the offending change will be reverted.
+
+  Userspace applications can, however, expect the format and contents of
+  the attribute files to remain consistent in the absence of a version
+  attribute change in the context of a given attribute.