Messages in this thread |  | | | Date | Tue, 9 Aug 2005 15:47:49 +0100 (BST) | | From | Hugh Dickins <> | | Subject | Re: [RFC][patch 0/2] mm: remove PageReserved |
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On Tue, 9 Aug 2005, Benjamin Herrenschmidt wrote: > > > ioremap is making a similar check to the one remap_pfn_range used > > to make; but I see no good reason for it at all. ioremap should be > > allowed to map whatever the caller asked, just as memset is allowed > > to set whatever the caller asked. > > This is dodgy actually. memset can't be guaranteed to work on IOs or > other non-cacheable memory (including real RAM that has been mapped > non-cacheable, typically RAM that has been "set aside" for other uses as > described above, wether it's for AGP, or for some weird processor DMA > bounce buffers or whatever ..., that is RAM that is out of the normal > kernel control).
That was my point: memset goes ahead without making funny little checks, and works or not, so I don't see why ioremap needs to make these funny little checks. If the driver doesn't know what it's doing (not impossible, I accept), what's the likelihood that PageReserved or not will save it?
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