On Fri, Oct 18, 2013 at 10:57:24AM -0500, Rob Herring wrote: > On 10/18/2013 08:28 AM, Pantelis Antoniou wrote: > > Hi Michael, > > > > On Oct 18, 2013, at 5:54 AM, Michael Bohan wrote: > > > >> 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. > >> > > > > I guess it's time for another try to getting it in? > > > > DT maintainers, which one of you will want to review? > > This falls in Grant's and my plate since we are talking kernel DT > support code rather than bindings. Unflattening is definitely the right > direction to go here. > I think Pantelis may have been asking about his devicetree overlay support patch series. Pantelis, did you have time to address the review comments you got earlier ? Thanks, Guenter -- 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
