On Thu, Nov 12 2015 at 01:19:59 PM, Michael Ellerman <mpe@xxxxxxxxxxxxxx> wrote: > On Tue, 2015-09-15 at 18:30 -0700, Mitchel Humpherys wrote: > >> Any overlap in the reserved memory regions (those specified in the >> reserved-memory DT node) is a bug. > > Can you expand a bit on why you think it's a bug? I assume it was discussed at > some point on the list but I didn't see it sorry. The reason I think it's a bug is because the overlapping memory could be handed out to multiple firmwares, which generally ends in "random" firmware crashes. We've found by sad experience that root-causing such a crash can be quite difficult. Is there a valid use case for overlapping regions? I can't think of one... > There's nothing I can see in the binding document[1] about whether regions can > overlap, or what it would mean if they did. You're right, the bindings document doesn't say anything about overlapping memory regions. I can submit something unless someone comes up with a reason why we should allow overlapping memory regions. > If we want to declare that overlapping regions are always a bug then there > should be some text in the binding explaining that. There's also the > possibility that we have existing device trees in the wild that contain > overlapping regions, and whether we think it's OK to retrospectively declare > that they're incorrect. I did a quick survey of in-tree users of reserved-memory and couldn't find any overlapping regions. -Mitch -- Qualcomm Innovation Center, Inc. The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
