On Tue, Aug 13, 2013 at 04:54:02PM +0100, Stephen Warren wrote: > On 08/13/2013 03:08 AM, Mark Rutland wrote: > > On Mon, Aug 12, 2013 at 06:36:30PM +0100, Stephen Warren wrote: > >> From: Stephen Warren <swarren@xxxxxxxxxx> > >> > >> The simplest case of __of_parse_phandle_with_args() implements > >> of_parse_phandle(), except that it doesn't return the node referenced by > >> the phandle. Modify it to do so, and then rewrite of_parse_phandle() to > >> call __of_parse_phandle_with_args() rather than open-coding the simple > >> case. > > > > That commit message doesn't seem to match the patch (which doesn't > > modify __of_parse_phandle_with_args). > > > > Rather, now that __of_parse_phandle_with_args can handle parsing with a > > fixed number of argument cells, it's possible to write of_parse_phandle > > in terms of it. > > True. I originally hadn't realized that __of_parse_phandle_with_args() > does already return the node and so started to add that feature, then > forgot to re-write the commit description. How about: > > ----- > of: call __of_parse_phandle_with_args from of_parse_phandle > > The simplest case of __of_parse_phandle_with_args() now implements the > semantics of of_parse_phandle(). Rewrite of_parse_phandle() to call > __of_parse_phandle_with_args() rather than open-coding the simple case. > ----- Sounds good to me! > > > What's the overhead over the old of_parse_phandle? It looks like this is > > going to do a lot of pointless work beyond what it already does -- > > parsing each prior entry in the list, and for each prior entry walking > > the tree in of_find_node_by_phandle. Maybe we don't use long enough > > phandle lists anywhere for that to be noticeable. > > I think the overhead is pretty minimal. The main difference is that the > new code will loop over the property cell by cell rather than directly > jump into the required index. That's not likely to be much work for > typical properties. In particular, no extra DT property lookups are > performed, since of_parse_phandle() passes in cells_name=NULL, > cell_count=0, so the cells_name property is not looked up. I thought even with your patch we still call of_find_node_by_phandle on each (phandle) cell as we go over the property, before we hit the check for cells_name? Given that of_find_node_by_phandle does a pretty naive linear search of the of_allnodes list, that could get significant, especially if all the elements referred to in the property are near the end of the of_allnodes list. > > Besides, Grant told me to do this change:-) > A Likely story... :) Thanks, Mark. -- 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
