Re: [PATCH] bootmem.c clean up bad pfn convertions

[Franck Bui-Huu <franck.bui-huu@innova-card.com>]

Dave Hansen wrote:

>The only arch with phys_to_pfn() defined is UML, so the patch simply
>won't compile anything but UML on current kernels (unless I'm missing
>something).
>  
>
oops, I forgot to send the part of the patch that defines these macros, 
sorry.

>Could you try to give us a more complete description of your problem?  I
>know your memory doesn't start at 0x0, but what problems does that
>cause?  Does the mem_map[] allocation blow up, etc...  
>  
>
yes, it actually intends to solve that.

>If it's just mem_map[], That calculation could be fixed pretty easily.
>Something like
>
>+#ifdef CONFIG_CRAZY_MIPS_FOO_MEM_MAP_START... 
>+extern unsigned long mem_map_start_pfn
>+#else
>+#define mem_map_start_pfn 0UL
>+#endif
>-#define pfn_to_page(pfn)        (mem_map + (pfn))
>+#define pfn_to_page(pfn)        (mem_map + (pfn) - mem_map_start_pfn)
>
>
>  
>
This is another solution indeed...But you will have to define another 
constant which
will be used for virtual to physical address convertion. In my case I have

#define phys_to_pfn(x)        (((x) - PHYS_START) >> PAGE_SHIFT)
#define pa(x)       ((x) - PAGE_OFFSET + PHYS_START)

and "pfn_to_page" stays untouch.
But I expect your solution easier to implement since as you said 
previously no arch
defines "phys_to_pfn".

Thanks

          Franck.

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