* Dave Hansen ([EMAIL PROTECTED]) wrote: > On Fri, 2007-11-16 at 09:47 -0500, Mathieu Desnoyers wrote: > > * Dave Hansen ([EMAIL PROTECTED]) wrote: > > > For most (all?) architectures, the PFN and the virtual address in the > > > kernel's linear are interchangeable with pretty trivial arithmetic. All > > > pages have a pfn, but not all have a virtual address. Thus, I suggested > > > using the pfn. What kind of virtual addresses are you talking about? > > > > > > > Hrm, in asm-generic/memory_model.h, we have various versions of > > __page_to_pfn. Normally they all cast the result to (unsigned long), > > except for : > > > > > > #elif defined(CONFIG_SPARSEMEM_VMEMMAP) > > > > /* memmap is virtually contigious. */ > > #define __pfn_to_page(pfn) (vmemmap + (pfn)) > > #define __page_to_pfn(page) ((page) - vmemmap) > > > > So I guess the result is a pointer ? Should this be expected ? > > Nope. 'pointer - pointer' is an integer. Just solve this equation for > integer: > > 'pointer + integer = pointer' >
Well, using page_to_pfn turns out to be ugly in markers (and in printks) then. Depending on the architecture, it will result in either an unsigned long (x86_64) or an unsigned int (i386), which corresponds to %lu or %u and will print a warning if we don't cast it explicitly. Mathieu > -- Dave > -- Mathieu Desnoyers Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
