Re: How to document dimension units for virtual files?
From: Michael Holzheu
Date: Tue Oct 24 2006 - 10:14:35 EST
Ingo Oeser <ioe-lkml@xxxxxxxxxx> wrote on 10/23/2006 09:03:32 PM:
> > 2. Encode dimension unit into filename (e.g. onlinetime_ms or
> This is the recommended one.
> - simple to implement and understand on both sides
> - if you change units, you notice breaking userspace immediately
> and can even notice it being used in closed source tools
> with a simple strace
> - no parsing involved, as the author of the user space tool
> usually assumes the unit implicitly (like "programming by contract",
> the "contract" is the filename, which is quite easy to check for.
> - you can keep a legacy interface with neglible effort and code wastage
> - many advantages I forgot :-)
I also think that this is the best solution. It would be nice to have
that documented somewhere. Maybe in the Documentation directory
Howto export data in virtual files
If you want to export data to userspace via virtual filesystems
like procfs, sysfs, debugfs etc., the following rules are recommended:
- Export only one value in one virtual file.
- Data format should be as simple as possible.
- Use ASCII formated strings, no binary data if possible.
- If data has dimension units, encode that in the filename.
Please use the following suffixes:
* kb: Kilobytes
* mb: Megabytes
* ms: Milliseconds
* us: Microseconds
* ns: Nanoseconds
> ls /sys/mydata
> cat /sys/mydata/memory_kb
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