[ +CC: Lee, Rob and device-tree list ] On Sat, Nov 11, 2017 at 09:50:59AM -0800, Dmitry Torokhov wrote: > On Sat, Nov 11, 2017 at 04:43:37PM +0100, Johan Hovold wrote: > > A helper purported to look up a child node based on its name was using > > the wrong of-helper and ended up prematurely freeing the parent of-node > > while searching the whole device tree depth-first starting at the parent > > node. > > Ugh, this all is pretty ugly business. Can we teach MFD to allow > specifying firmware node to be attached to the platform devices it > creates in mfd_add_device() so that the leaf drivers simply call > device_property_read_XXX() on their own device and not be bothered with > weird OF refcount issues or what node they need to locate and parse? Yeah, that may have helped. You can actually specify a compatible string in struct mfd_cell today which does make mfd_add_device() associate a matching child node. Some best practice regarding how to deal with MFD and device tree would be good to determine and document too. For example, when should of_platform_populate() be used in favour of mfd_add_device()? And how best to deal with sibling nodes, which is part of the problem here (I think the mfd should have provided a flag rather than having subdrivers deal with sibling nodes, for example). That said, driver authors using the wrong of-helper could possibly have been avoided by amending the kernel docs (I'll do that as a follow up), but once these incorrect usages get in, only review can prevent them from being reproduced through copy-paste coding. Johan -- 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
