On Fri, Feb 01, 2013 at 12:05:39PM +0000, Dimitris Papastamos wrote:

> +struct regmap_reg_range  {
> +	unsigned int start;
> +	unsigned int end;
> +	unsigned int attr;
> +};

> +	i = start_reg;
> +	while (i <= map->max_register) {
> +		reg_attr = regmap_attr_bitmap(map, i);
> +		switch (state) {

We're doing a linear scan through the entire register map here in order
to build up a list of which registers exist, doing it every time the
file is read.  This data structure looks *very* like the one we have for
the reads themselves, it seems like we should be sharing the work here
and using the same cache.