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? > Mike > > -- > Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, > hosted by The Linux Foundation Regards -- Pantelis -- 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
