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Commit 00e262fd authored by Darren Hart's avatar Darren Hart Committed by Greg Kroah-Hartman
Browse files

Documentation/sysfs-rules.txt: Add device attribute error code documentation 



Provide some entry-level statements about what to expect from sysfs
device attribute read/store return codes, both for users and kernel
developers.

Signed-off-by: default avatarDarren Hart <dvhart@linux.intel.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Azael Avalos <coproscefalo@gmail.com>
Cc: H. Peter Anvin <hpa@linux.intel.com>
Cc: Frans Klaver <fransklaver@gmail.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 9e82bf01

Documentation/sysfs-rules.txt

+21 −0
Original line number Original line Diff line number Diff line
@@ -161,3 +161,24 @@ versions of the sysfs interface. 
  the device that matches the expected subsystem. Depending on a specific

  the device that matches the expected subsystem. Depending on a specific

  position of a parent device or exposing relative paths using "../" to

  position of a parent device or exposing relative paths using "../" to

  access the chain of parents is a bug in the application.

  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.