On Wed, 20 Sep 2006, Andrew Morton wrote: > > Would it not make sense to define what ZONE_DMA actually means > > consistently before trying to change it? The current mess across > > different architectures seems like a disaster area to me. > > > > What DOES requesting ZONE_DMA from a driver actually mean?
ZONE_DMA is a memory area that is needed by an arch for devices that cannot do DMA to all of memory. The high boundary is set by MAX_DMA_ADDRESS. > My concern about these patches is that they'll only be useful for > self-compiled kernels, because distros will be forced to enable ZONE_DMA > for evermore anyway. We already have 4 arches now that do not need ZONE_DMA at all. ZONE_DMA does not have a bright future with IOMMUs and other things around. None of my system uses ZONE_DMA and I have a variety of them. And yes if we do not have this facility in the kernel then distros cannot pick it up. At least on IA64 I know that hardware from the major vendors has not been needing ZONE_DMA for a while now. Also ZONE_DMA is a very bad concept. Multiple drivers may have different address requirements. What we need is some way for a driver to tell the kernel what the required range of addresses is. If a device is only capable of handling 30 valid address bits then we may have to use ZONE_DMA and only allow the use of the lower 16MB. It would be better to develop a different mechanism. - To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
