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. -- To unsubscribe from this list: send the line "unsubscribe linux-tegra" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
