On Mon, Apr 20, 2015 at 10:24:25PM +0200, Ricardo Ribalda Delgado wrote: > Hi Bjorn! > > Thanks for your promtly response. > > On Mon, Apr 20, 2015 at 9:28 PM, Bjorn Helgaas <[email protected]> wrote: > > [+cc Grant (author of ac80a51e2ce5)] > > > > Hi Ricardo, > > > > On Mon, Apr 20, 2015 at 06:22:52PM +0200, Ricardo Ribalda Delgado wrote: > >> > >> If of_platform_depopulate is called later, resource->parent is > >> accessed (Offset 0x30 of address 0), causing a kernel error. > > > > Interesting; how'd you find this? It looks like the > > of_platform_depopulate() code has been this way for a long time, so we > > must be doing something new that makes us trip over this now. More > > analysis below... > > I have an out of tree driver that dynamically adds devices to the device tree. > > It was developed before the dynamic_of and dt_overlays existed. Now I > am porting my code to the new interfaces available. I am trying to do > it small steps. > > First step was being able to depopulate a previously loaded device > tree. Old, code was calling of_platform_populate, so calling > of_platform_depopulate looked like the right choice. Unfortunately > everything crashed, and it turned out that this was the issue. > > On my defense I would say, that the plan is to make this driver > public, once the hardware is stabilized and sold to the public.
No need to defend yourself; to me this looks like a bug in the of_platform code, so it's a good thing you tripped over it :) The obvious bug is the NULL pointer dereference. The not-quite-so- obvious bug is that I think the lack of insert_resource() means the resource tree (/proc/iomem, /proc/ioports) is missing some useful information. > > From reading drivers/base/platform.c, it looks like the intent is > > that platform device users would use these interfaces: > > I can take a look to modify OF to use insert_resource(), but I still > think that no matter what, we should add this extra check, like the > propossed patch or maybe with a BUG_ON().... I think it would be nicer to make OF use platform_device_add_resources() and platform_device_add() because then there's less duplication of code. But Grant might have had a reason for avoiding that. Bjorn -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
