On Thu, Jul 13, 2017 at 02:40:12PM -0700, Frank Rowand wrote: > On 07/13/17 14:22, Phil Elwell wrote: > > On 13/07/2017 21:07, Frank Rowand wrote: > >> On 07/13/17 12:38, Phil Elwell wrote: > >> > >> (I moved Phil's reply to after the email he replied to.) > > > > Thanks. > > > >>> On 13 Jul 2017 8:32 pm, "Frank Rowand" <frowand.list@xxxxxxxxx> wrote: > >>> > >>>> On 07/03/17 02:06, David Gibson wrote: > >>>>> On Wed, Jun 14, 2017 at 05:52:25PM +0300, Pantelis Antoniou wrote: > >>>>>> This patch enables an overlay to refer to a previous overlay's > >>>>>> labels by performing a merge of symbol information at application > >>>>>> time. > >>>>> > >>>>> This seems to be doing things the hard way. > >>>>> > >>>>> You're essentially extending the semantics of overlay application to > >>>>> add the symbol merging. You've implemented these extended semantics > >>>>> in libfdt, which is all very well, but that's not the only overlay > >>>>> application implementation. > >>>>> > >>>>> > >>>>> It seems to me a better approach would be to change dtc's -@ > >>>>> implementation, so that in /plugin/ mode instead of making a global > >>>>> __symbols__ node, it puts it into the individual fragments. That way > >>>>> the existing overlay application semantics will update the __symbols__ > >>>>> node. > >>>> > >>>> If the __symbols__ node was inside a fragment, then the existing > >>>> code would add (or update) a __symbols__ node located at the location > >>>> pointed to by the fragment's target path, instead of updating the > >>>> node /__symbols__. > >>>> > >>>> It makes sense to me to have only one global __symbols__ node instead > >>>> of several. > >>>> > >>>> If there is a global __symbols__ node then we have a single name > >>>> space for symbols. > >>>> > >>>> If there are multiple __symbols__ nodes spread throughout the tree, > >>>> then to me that would imply different name spaces spread throughout > >>>> the tree, where namespaces are determined by fragments. This sounds > >>>> confusing to me. Or if the intent is to have a single name space > >>>> then the __symbols__ information would be scattered throughout the > >>>> tree instead of located in a single node. > >>>> > >>>> My current patch (under review), targeted for Linux 4.13-rc1, puts > >>>> an overlay's __symbols__ node properties into the overlay's > >>>> changeset, so they get added when the overlay is loaded and > >>>> removed when the overlay is unloaded. > >> > >>> Can we also consider a mechanism for overlay-local symbols, i.e. symbols > >>> that are used purely to create links within an overlay - perhaps using a > >>> particular naming convention? This would make it easier to instantiate an > >>> overlay multiple times without having to uniquify all symbols, and it would > >>> avoid polluting the global namespace without reason. > >>> > >>> Phil > >> > >> That is essentially the result you get if you compile the overlay dts > >> without '-@'. There will be no __symbols__ node created even if there > >> are symbols within the overlay. > > > > But (unless something has changed recently) the '-@' switch controls both > > symbol and fixup generation, i.e. export and import of symbols. Unless one > > religiously uses 'target-path' to place fragments (thus removing the > > level of abstraction provided by symbols) overlays are useless without > > the ability to reference external symbols, but in my experience very few > > overlays need to add symbols to the global symbol table. > > For the dtc compiler in Linux 4.11, the '-@' switch is only needed > to generate the __symbols__ node. The __fixups__ and __local-fixups__ > nodes are generated whether '-@' is specified or not. > > The __fixups__ and __local_fixups__ are generated when '/plugin/;' > is specified in the source file. Yup, i.e. something *has* changed recently. Building fixups based on -@ never made any sense. -- David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ | _way_ _around_! http://www.ozlabs.org/~dgibson
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