Re: [PATCH 1/3] PM / Domains: Allow overriding the ->xlate() callback

[Thierry Reding <thierry.reding-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

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On Tue, Mar 14, 2017 at 08:34:01PM +0000, Jon Hunter wrote:
> 
> On 14/03/17 19:15, Thierry Reding wrote:
> > From: Thierry Reding <treding-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
> > 
> > Allow generic power domain providers to override the ->xlate() callback
> > in case the default genpd_xlate_onecell() translation callback is not
> > good enough.
> > 
> > One potential use-case for this is to allow generic power domains to be
> > specified by an ID rather than an index.
> 
> Are you sure this is necessary, because I recall that the genpd core
> does allow for holes in the domain array (which is what we have). See
> commit 609bed67bd8f ('PM / Domains: Allow holes in genpd_data.domains
> array').

I suppose we could use that, but it feels like the wrong solution to me.
Why would we want to deal with holes in the array when we can simply do
all the required work at probe time and add only the existing domains in
any particular SoC.

For example on Tegra186 we've got a maximum ID of 43, so we'd need to
allocate 44 pointers, but we only use 17 of those IDs. People usually
reply to that that newer SoCs come with enough memory to make this
waste irrelevant. I don't buy that. Why should we waste memory if it
can be easily avoided?

Thierry

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