On Tue, Oct 06 2015 at 05:35:41 PM, Rob Herring <robherring2@xxxxxxxxx> wrote: > On Tue, Oct 6, 2015 at 3:47 PM, Laura Abbott <labbott@xxxxxxxxxxxxxxxxx> wrote: [...] >> +Example: >> + >> + ion { >> + compatbile = "linux,ion"; >> + #address-cells = <1>; >> + #size-cells = <0>; >> + >> + ion-system-heap { >> + linux,ion-heap-id = <0>; >> + linux,ion-heap-type = <ION_SYSTEM_HEAP_TYPE>; >> + linux,ion-heap-name = "system"; > > How does this vary across platforms? Is all of this being pushed down > to DT, because there is no coordination of this at the kernel ABI > level across platforms. In other words, why can't heap 0 be hardcoded > as system heap in the driver. It seems to me any 1 of these 3 > properties could be used to derive the other 2. The heap-id<->heap-type mapping isn't necessarily 1:1. As Laura indicated elsewhere on this thread, a given heap might need to be contiguous on one platform but not on another. In that case you just swap out the heap-type here and there's no need for userspace to change. The heap-name, OTOH, could be derived from the heap-id, which is what we hackishly do here [1] and here[2]. [1] https://www.codeaurora.org/cgit/quic/la/kernel/msm-3.14/tree/drivers/staging/android/ion/msm/msm_ion.c?h=msm-3.14#n53 [2] https://www.codeaurora.org/cgit/quic/la/kernel/msm-3.14/tree/drivers/staging/android/ion/msm/msm_ion.c?h=msm-3.14#n398 -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