On Thu, 21 Nov 2013 11:57:00 -0700, Stephen Warren <swarren@xxxxxxxxxxxxx> wrote: > On 11/21/2013 10:17 AM, Hiroshi Doyu wrote: > > Iterating over a property containing a list of phandles with arguments > > is a common operation for device drivers. This patch adds a new > > of_property_for_each_phandle_with_args() macro to make the iteration > > simpler. > > > > Signed-off-by: Hiroshi Doyu <hdoyu@xxxxxxxxxx> > > --- > > v6+: > > Use the description, which Grant Likely proposed, to be full enough > > that a future reader can figure out why a patch was written. > > http://lists.linuxfoundation.org/pipermail/iommu/2013-November/007062.html > > This new version only addresses one of the concerns that Grant had, > namely the commit message. > > > diff --git a/include/linux/of.h b/include/linux/of.h > > > +#define of_property_for_each_phandle_with_args(np, list, cells, i, args) \ > > + for (i = 0; !of_parse_phandle_with_args(np, list, cells, i, args); i++) > > + > > Grant also wanted the actual implementation fixed so that it wasn't so > inefficient. > > What this current patch does is basically: > > for every entry in the property: > for every entry in the property before the current index: > parse the phandle+specifier > > That's roughly O(n^2). (n is # entries in the property) > > Instead, what should happen is: > > for every entry in the property: > parse the phandle+specifier > yield the result > > That's roughly O(n). > > In other words, an implementation more along the lines of > include/linux/of.h's: > > #define of_property_for_each_u32(np, propname, prop, p, u) \ > for (prop = of_find_property(np, propname, NULL), \ > p = of_prop_next_u32(prop, NULL, &u); \ > p; \ > p = of_prop_next_u32(prop, p, &u)) > > ... so you'd need functions like of_prop_first_specifier() and > of_prop_next_specifier(), and perhaps some associated set of state > variables, perhaps with all the state wrapped into a single struct for > simplicity. That's right, I forgot I said that. Yes please fix the implementation. g. -- 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
