[PATCH V2] mm/ioremap: Probe platform for p4d huge map support

Stephen Rothwell sfr at canb.auug.org.au
Fri Jul 12 18:40:55 AEST 2019

Hi all,

On Fri, 12 Jul 2019 17:07:48 +1000 Michael Ellerman <mpe at ellerman.id.au> wrote:
> The return value of arch_ioremap_p4d_supported() is stored in the
> variable ioremap_p4d_capable which is then returned by
> ioremap_p4d_enabled().
> That is used by ioremap_try_huge_p4d() called from ioremap_p4d_range()
> from ioremap_page_range().

When I first saw this, I wondered if we expect
arch_ioremap_p4d_supported() to ever return something that is not
computable at compile time.  If not, why do we have this level of
redirection?  Why not just make it a static inline functions defined in
an arch specific include file (or even just a CONFIG_ option)?

In particular, ioremap_p4d_enabled() either returns ioremap_p4d_capable
or 0 and is static to one file and has one call site ...  The same is
true of ioremap_pud_enabled() and ioremap_pmd_enabled().
Stephen Rothwell
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