Re: [PATCH 1/4] tools/power turbostat: Add --no-msr option

[Patryk Wlazlyn <patryk.wlazlyn@linux.intel.com>]

> 6.7 added probe_platform_features().
> 
> Perhaps after it runs, we can simply update the result to disable
> those impacted by no_msr?
> 
> platform->has_cst_msrs = 0;
> platform->has_nhm_msrs = 0;
> platform->rapl_msrs = 0;
> etc.
> 
> that would avoid having to scatter no_msr in a lot of places.
> 
> of course that begs the question of what to do when a feature is
> available both via MSR and via perf -- which is about to happen...
> 
> it also adds a place for us to make an error when we add a feature --
> but even if we had a table and a bit to say whether the feature is
> available via msr, we'd still have the opportunity to mess that up...

Right. I thought about it, but I didn't like the idea of modifying the
platform information, because of the reasons you outlined above, but
also we might have some logic, along the way that cares if something is
present, but not necessarily use MSR driver (or any other method) to get it.

With these changes, sure there are some no_msr checks scattered around,
but they are usually close to where the data is acquired, making it easy
to add an alternative path.

Modifying the platform_features would require to "unconst" a lot of the
structures.

I think it's more clear to store a platform information in the
platform_features and leave no_msr just to store whether the user
requested the mode. This comes with a few extra checks, but leaves the
structures independent.