On Mon, 8 Jun 2015 22:02:06 +0200 , Ricardo Ribalda Delgado <ricardo.ribalda@xxxxxxxxx> wrote: > Hello Grant > > On Mon, Jun 8, 2015 at 8:23 PM, Grant Likely <grant.likely@xxxxxxxxxx> wrote: > > On Fri, 5 Jun 2015 12:51:17 +0200 > > , Ricardo Ribalda Delgado <ricardo.ribalda@xxxxxxxxx> > > wrote: > >> Some device tree platforms have not defined correctly their memory > >> resources (i.e. Overlapping or duplication of resources). > >> To avoid this issue we have historically avoided to add their resources to > >> the resource tree. This leads to code duplication and oops when trying to > >> unload dynamically a device tree (feature introduced recently). > >> > >> This new flag tells the resource system that a resource can be shared by > >> multiple owners, so we can support device trees with problems at the > >> same time that we do not duplicate code or crash when unloading the > >> device tree. > >> > >> Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@xxxxxxxxx> > >> --- > > > > I'm really not comfortable with this change. The resource tree code is > > complicated enough as is. Adding this exception case quite probably adds > > corner cases that aren't property dealt with. If two regions overlay, > > and then request_region is called? Which region does it become a child > > of? And that's just off the top of my head. I don't want to hack in > > changes to the resource code for what is a corner case. > > I see your concern, perhaps you could provide a testcase and we can > find out if it fails or not. So far I have tested a device tree with > two devices on the same memory region, each device managed by a > driver. Actually, you need to provide the test case. You need to show that you've thought through all the implications and corner cases on the resource code. This is a non-trivial change to the how the resource code works, and you need to demonstrate that your really understand the implications of what you are doing. Start with the example I pointed out. When a driver does a request_mem_region(), which resource does it end up being a parent of if the regions overlap? Can you write a unittest that demonstrates the code has the correct behaviour? Will a driver end up getting the wrong device's resource structure as the parent? (hint: yes it will) > I can load and unload the device tree perfectly. Merely making it work for your use-case isn't the issue. It's whether or not making this change will break the core behavour of the resource code. g. -- 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
