On Tuesday 12 September 2006 00:27, Christoph Lameter wrote: > x86_64: optional ZONE_DMA/ZONE_DMA32 > > Allow the use to specify CONFIG_ZONE_DMA32 and CONFIG_ZONE_DMA (via > CONFIG_GENERIC_ISA_DMA). > > If CONFIG_ZONE_DMA is off then devices requiring ISA DMA can no > longer be selected. > > There are no drivers depending on CONFIG_ZONE_DMA32. If CONFIG_ZONE_DMA32 > is not set then the system assumes that DMA devices are capable of > doing DMA to all of memory (which is mostly the case since most > x86_64 motherboards only allow a max of 4GB of memory and advanced > systems have DMA subsystems that handle I/O properly). Pretty much all have this problem (or do you know of a system with no USB controller?) I think I would prefer to not make GFP_DMA32 optional. Adding a 4GB limit CONFIG to a 64bit kernel just seems somewhat dumb. Also what happens when someone still sets GFP_DMA? iirc the SCSI stack tended to do that for some structures. Will it fail? Making GFP_DMA optional would be an interesting experiment (I think it will break the floppies but other than that a modern system might be fine). But it would be better to warn the user stronger against it (most likely it will still break a lot of older addin cards) and tell them about the floppy. BTW we still call it x86-64, not x64. -Andi - To unsubscribe from this list: send the line "unsubscribe linux-ia64" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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