On Fri, 2005-02-04 at 13:36 +0100, Arnd Bergmann wrote:
> On Freedag 04 Februar 2005 08:22, Olof Johansson wrote:
> > It's getting pretty old to have see and type cur_cpu_spec->cpu_features
> > & CPU_FTR_<feature>, when a shorter and less TLA-ridden macro is more
> > readable.
> >
> > This also takes care of the differences between PPC and PPC64 cpu
> > features for the common code; most places in PPC could be replaced with
> > the macro as well.
>
> I have a somewhat similar patch that does the same to the
> systemcfg->platform checks. I'm not sure if we should use the same inline
> function for both checks, but I do think that they should be used in a
> similar way, e.g. CPU_HAS_FEATURE(x) and PLATFORM_HAS_FEATURE(x).
Note that I would prefer cpu_has_feature(), it doesn't strictly have to
be a macro and has function semantics anyway.
> My implementation of the platform checks tries to be extra clever by turning
> runtime checks into compile time checks if possible. This reduces code size
> and in some cases execution speed. It can also be used to replace compile
> time checks, i.e. it allows us to write
>
> static inline unsigned int readl(const volatile void __iomem *addr)
> {
> if (platform_is(PLATFORM_PPC_ISERIES))
> return iSeries_readl(addr);
> if (platform_possible(PLATFORM_PPC_PSERIES))
> return eeh_readl(addr);
> return in_le32();
> }
>
> which will always result in the shortest code for any combination of
> CONFIG_PPC_ISERIES, CONFIG_PPC_PSERIES and the other platforms.
That's a good idea !
> The required code for this is roughly
>
> enum {
> PPC64_PLATFORM_POSSIBLE =
> #ifdef CONFIG_PPC_ISERIES
> PLATFORM_ISERIES |
> #endif
> #ifdef CONFIG_PPC_PSERIES
> PLATFORM_PSERIES |
> #endif
> #ifdef CONFIG_PPC_PSERIES
> PLATFORM_PSERIES_LPAR |
> #endif
> #ifdef CONFIG_PPC_POWERMAC
> PLATFORM_POWERMAC |
> #endif
> #ifdef CONFIG_PPC_MAPLE
> PLATFORM_MAPLE |
> #endif
> 0,
> PPC64_PLATFORM_ONLY =
> #ifdef CONFIG_PPC_ISERIES
> PLATFORM_ISERIES &
> #endif
> #ifdef CONFIG_PPC_PSERIES
> PLATFORM_PSERIES &
> #endif
> #ifdef CONFIG_PPC_POWERMAC
> PLATFORM_POWERMAC &
> #endif
> #ifdef CONFIG_PPC_MAPLE
> PLATFORM_MAPLE &
> #endif
> -1ul,
> };
>
> static inline platform_is(unsigned long platform)
> {
> return ((PPC64_PLATFORM_ONLY & platform)
> || (PPC64_PLATFORM_POSSIBLE & platform & systemcfg->platform));
> }
>
> static inline platform_possible(unsigned long platform)
> {
> reutrn !!(PPC64_PLATFORM_POSSIBLE & platform);
> }
>
> The same stuff is obviously possible for cur_cpu_spec->cpu_features as well.
> Do you think that it will help there?
>
> Arnd <><
> _______________________________________________
> Linuxppc64-dev mailing list
> [EMAIL PROTECTED]
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--
Benjamin Herrenschmidt <[EMAIL PROTECTED]>
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