On Fri, Jun 10, 2011 at 03:16:00PM -0700, David Rientjes wrote: > On Fri, 10 Jun 2011, Russell King - ARM Linux wrote: > > > > We're talking about two different things. Linus is saying that if GFP_DMA > > > should be a no-op if the hardware doesn't require DMA memory because the > > > kernel was correctly compiled without CONFIG_ZONE_DMA. I'm asking about a > > > kernel that was incorrectly compiled without CONFIG_ZONE_DMA and now we're > > > returning memory from anywhere even though we actually require GFP_DMA. > > > > How do you distinguish between the two states? Answer: you can't. > > > > By my warning which says "enable CONFIG_ZONE_DMA _if_ needed." The > alternative is to silently return memory from anywhere, which is what the > page allocator does now, which doesn't seem very user friendly when the > device randomly works depending on the chance it was actually allocated > from the DMA mask. If it actually wants DMA and the kernel is compiled > incorrectly, then I think a single line in the kernel log would be nice to > point them in the right direction. Users who disable the option usually > know what they're doing (it's only allowed for CONFIG_EXPERT on x86, for > example), so I don't think they'll mind the notification and choose to > ignore it. So those platforms which don't have a DMA zone, don't have any problems with DMA, yet want to use the very same driver which does have a problem on ISA hardware have to also put up with a useless notification that their kernel might be broken? Are you offering to participate on other architectures mailing lists to answer all the resulting queries? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>