Re: do we have a generic string-number sysctl mapping library ?

On Fri, 27 Jun 2014 11:14+0200, Luigi Rizzo wrote:

> Hi,
> I have frequently found myself using sysctls to control some kernel
> feature where a string would be a better (and sometimes the only)
> option than using a numeric value, yet the internal representation
> should be numeric for speed and robustness.
> Examples are the kern.timecounter, the default scheduler in dummynet,
> and now in netmap the selection between native and emulated mode.
> I am sure many of you can come up with other cases.
> =

> I wonder if we have some support for that already in the sysctl code,
> or i should build a generic one next time i need to do that.

In C, according to sysctl(3) you could use sysctlnametomib().
I might have misinterpreted the problem domain.

> Feel free to criticise the approach and suggest better ones.
> Right now i am using sysctls because i have a set of macros
> and wrapper functions that let me convert them to sysfs
> entries when building kernel code on linux, so I have a
> portable solutions.
> =

> For the details, I'd like to have a mechanism that requires the
> kernel programmer supply a (possibly extensible) table of
> supported values, and matching constants to be used within
> the kernel. A single declaration should generate entries
> to get/set the current value as well as list options.
> We can discuss frills (such as wildcards, multiple values,etc).
> =

> cheers
> luigi

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