On Thu, Oct 17, 2013 at 05:44:07PM -0700, Guenter Roeck wrote: > On 10/17/2013 04:51 PM, Michael Bohan wrote: > >On Wed, Oct 16, 2013 at 09:54:27PM -0700, Guenter Roeck wrote: > >>Still, what prevents you from unflattening it and just using the > >>normal device tree functions as David suggested ? > > > >I'm assuming you're suggesting to use of_fdt_unflatten_tree()? > > Yes, that was the idea. > > >That's an interesting thought. I was planning to scan the fdt > >only once and populate my own structures, but I suppose I could > >use the of_* APIs equivalently. > > > >It seems there are some problems though. of_fdt_unflatten_tree() > >does not return errors, and so for the purposes of my driver it > >would not be sufficient to detect an invalid firmware image. > > > It does so, at least partially. If there is an error, it won't set > the nodes pointer. Granted, that is not perfect, but it is at least > a start. Ultimately, I considered it 'good enough' for my purpose > (for devicetree overlays - see [1] below), as any missing mandatory > properties or nodes are detected later when trying to actually read > the properties. In my case, I also have a couple of validation > properties to ensure that the overlay is acceptable (specifically > I use 'compatible' and 'assembly-ids', but that is really a detail). That's certainly better than nothing, but I think it would be useful to make a distinction between a malformed fdt and a fdt that's simply missing the right information. Without error codes, I think we lose this aspect. > >Would people entertain changing this API > >(and implicitly __unflatten_device_tree) to return errors? I'm > >guessing the reason it's coded that way is because the normal > >usecase is 'system boot', at which time errors aren't that > >meaningful. > > > >Also, there's no way to free the memory that was allocated from > >the unflatten process. May I add one? > > > > The patchset submitted by Pantelis Antoniou to add support for > devicetree overlays adds this and other related functionality. > See [1], specifically the patch titled "OF: Introduce utility > helper functions". Not sure where that is going, though. > It may need some cleanup to be accepted upstream. > Copying Pantelis for comments. > Guenter > > [1] https://lkml.org/lkml/2013/1/4/276 Thanks. So it seems that Pantelis's __of_free_tree() is what I'm looking for. Mike -- Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation -- To unsubscribe from this list: send the line "unsubscribe linux-arm-msm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
