linux-kernel - Re: [PATCH 3/8] regmap: Add the rbtree cache support

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Message-ID: <4E613B22.7000908@metafoo.de>
Date:	Fri, 02 Sep 2011 22:22:58 +0200
From:	Lars-Peter Clausen <lars@...afoo.de>
To:	Dimitris Papastamos <dp@...nsource.wolfsonmicro.com>
CC:	linux-kernel@...r.kernel.org,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	Liam Girdwood <lrg@...com>,
	Graeme Gregory <gg@...mlogic.co.uk>,
	Samuel Oritz <sameo@...ux.intel.com>
Subject: Re: [PATCH 3/8] regmap: Add the rbtree cache support

On 09/02/2011 05:46 PM, Dimitris Papastamos wrote:
> This patch adds support for the rbtree cache compression type.
> 
> Each rbnode manages a variable length block of registers.  There can be no
> two nodes with overlapping blocks.  Each block has a base register and a
> currently top register, all the other registers, if any, lie in between these
> two and in ascending order.
> 
> The reasoning behind the construction of this rbtree is simple.  In the
> snd_soc_rbtree_cache_init() function, we iterate over the register defaults
> provided by the regcache core.  For each register value that is non-zero we
> insert it in the rbtree.  In order to determine in which rbnode we need
> to add the register, we first look if there is another register already
> added that is adjacent to the one we are about to add.  If that is the case
> we append it in that rbnode block, otherwise we create a new rbnode
> with a single register in its block and add it to the tree.
> 
> There are various optimizations across the implementation to speed up lookups
> by caching the most recently used rbnode.
> 
> Signed-off-by: Dimitris Papastamos <dp@...nsource.wolfsonmicro.com>
> [...]
> +
> +static int regcache_rbtree_init(struct regmap *map)
> +{
> +	struct regcache_rbtree_ctx *rbtree_ctx;
> +	int i;
> +	int ret;
> +
> +	map->cache = kmalloc(sizeof *rbtree_ctx, GFP_KERNEL);
> +	if (!map->cache)
> +		return -ENOMEM;
> +
> +	rbtree_ctx = map->cache;
> +	rbtree_ctx->root = RB_ROOT;
> +	rbtree_ctx->cached_rbnode = NULL;
> +
> +	if (!map->cache_defaults)
> +		return 0;
> +
> +	for (i = 0; i < map->num_cache_defaults_raw; ++i) {
> +		ret = regcache_lookup_reg(map, i);
> +		if (ret < 0)
> +			continue;
> +		ret = regcache_rbtree_write(map,
> +					    map->cache_defaults[ret].reg,
> +					    map->cache_defaults[ret].def);
> +		if (ret)
> +			goto err;
> +	}

You can iterate over the caches_defaults elements directly.

[...]
> diff --git a/drivers/base/regmap/regcache.c b/drivers/base/regmap/regcache.c
> index dfefe40..2b148d4 100644
> --- a/drivers/base/regmap/regcache.c
> +++ b/drivers/base/regmap/regcache.c
> @@ -19,6 +19,9 @@ static const struct regcache_ops *cache_types[] = {
>  #ifdef CONFIG_REGCACHE_INDEXED
>  	&regcache_indexed_ops,
>  #endif
> +#ifdef CONFIG_REGCACHE_RBTREE

This symbol is also not defined. It looks as if all the Kconfig changes are not
included in the patchset.

> +	&regcache_rbtree_ops,
> +#endif
>  };


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