Hi Ingo,
Ingo Oeser <[email protected]> wrote on 10/23/2006 09:03:32 PM:
[snip]
> > 2. Encode dimension unit into filename (e.g. onlinetime_ms or
memory_kb)
>
> 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",
where
> 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
something like:
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
* ...
Examples:
---------
> ls /sys/mydata
memory_kb
online_time_ms
> cat /sys/mydata/memory_kb
4769
Michael
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