drivers/of: Avoid recursively calling unflatten_dt_node()
In current implementation, unflatten_dt_node() is called recursively to unflatten device nodes in FDT blob. It's stress to limited stack capacity, especially to adopt the function to unflatten device sub-tree that possibly has multiple root nodes. In that case, we runs out of stack and the system can't boot up successfully. In order to reuse the function to unflatten device sub-tree, this avoids calling the function recursively, meaning the device nodes are unflattened in one call on unflatten_dt_node(): two arrays are introduced to track the parent path size and the device node of current level of depth, which will be used by the device node on next level of depth to be unflattened. All device nodes in more than 64 level of depth are dropped and hopefully, the system can boot up successfully with the partial device-tree. Also, the parameter "poffset" and "fpsize" are unused and dropped and the parameter "dryrun" is figured out from "mem == NULL". Besides, the return value of the function is changed to indicate the size of memory consumed by the unflatten device tree or error code. Signed-off-by: NGavin Shan <gwshan@linux.vnet.ibm.com> Acked-by: NRob Herring <robh@kernel.org> Signed-off-by: NRob Herring <robh@kernel.org>
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