drivers/base/regmap/regcache-rbtree.c - linux/kernel/git/viro/vfs - Git at Google

 /*
  * Register cache access API - rbtree caching support
  *
  * Copyright 2011 Wolfson Microelectronics plc
  *
  * Author: Dimitris Papastamos <dp@opensource.wolfsonmicro.com>
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 as
  * published by the Free Software Foundation.
  */

 #include <linux/slab.h>
 #include <linux/device.h>
 #include <linux/debugfs.h>
 #include <linux/rbtree.h>
 #include <linux/seq_file.h>

 #include "internal.h"

 static int regcache_rbtree_write(struct regmap *map, unsigned int reg,
 				 unsigned int value);
 static int regcache_rbtree_exit(struct regmap *map);

 struct regcache_rbtree_node {
 	/* the actual rbtree node holding this block */
 	struct rb_node node;
 	/* base register handled by this block */
 	unsigned int base_reg;
 	/* block of adjacent registers */
 	void *block;
 	/* number of registers available in the block */
 	unsigned int blklen;
 } __attribute__ ((packed));

 struct regcache_rbtree_ctx {
 	struct rb_root root;
 	struct regcache_rbtree_node *cached_rbnode;
 };

 static inline void regcache_rbtree_get_base_top_reg(
 	struct regmap *map,
 	struct regcache_rbtree_node *rbnode,
 	unsigned int *base, unsigned int *top)
 {
 	*base = rbnode->base_reg;
 	*top = rbnode->base_reg + ((rbnode->blklen - 1) * map->reg_stride);
 }

 static unsigned int regcache_rbtree_get_register(
 	struct regcache_rbtree_node *rbnode, unsigned int idx,
 	unsigned int word_size)
 {
 	return regcache_get_val(rbnode->block, idx, word_size);
 }

 static void regcache_rbtree_set_register(struct regcache_rbtree_node *rbnode,
 					 unsigned int idx, unsigned int val,
 					 unsigned int word_size)
 {
 	regcache_set_val(rbnode->block, idx, val, word_size);
 }

 static struct regcache_rbtree_node *regcache_rbtree_lookup(struct regmap *map,
 	unsigned int reg)
 {
 	struct regcache_rbtree_ctx *rbtree_ctx = map->cache;
 	struct rb_node *node;
 	struct regcache_rbtree_node *rbnode;
 	unsigned int base_reg, top_reg;

 	rbnode = rbtree_ctx->cached_rbnode;
 	if (rbnode) {
 		regcache_rbtree_get_base_top_reg(map, rbnode, &base_reg,
 						 &top_reg);
 		if (reg >= base_reg && reg <= top_reg)
 			return rbnode;
 	}

 	node = rbtree_ctx->root.rb_node;
 	while (node) {
 		rbnode = container_of(node, struct regcache_rbtree_node, node);
 		regcache_rbtree_get_base_top_reg(map, rbnode, &base_reg,
 						 &top_reg);
 		if (reg >= base_reg && reg <= top_reg) {
 			rbtree_ctx->cached_rbnode = rbnode;
 			return rbnode;
 		} else if (reg > top_reg) {
 			node = node->rb_right;
 		} else if (reg < base_reg) {
 			node = node->rb_left;
 		}
 	}

 	return NULL;
 }

 static int regcache_rbtree_insert(struct regmap *map, struct rb_root *root,
 				  struct regcache_rbtree_node *rbnode)
 {
 	struct rb_node **new, *parent;
 	struct regcache_rbtree_node *rbnode_tmp;
 	unsigned int base_reg_tmp, top_reg_tmp;
 	unsigned int base_reg;

 	parent = NULL;
 	new = &root->rb_node;
 	while (*new) {
 		rbnode_tmp = container_of(*new, struct regcache_rbtree_node,
 					  node);
 		/* base and top registers of the current rbnode */
 		regcache_rbtree_get_base_top_reg(map, rbnode_tmp, &base_reg_tmp,
 						 &top_reg_tmp);
 		/* base register of the rbnode to be added */
 		base_reg = rbnode->base_reg;
 		parent = *new;
 		/* if this register has already been inserted, just return */
 		if (base_reg >= base_reg_tmp &&
 		    base_reg <= top_reg_tmp)
 			return 0;
 		else if (base_reg > top_reg_tmp)
 			new = &((*new)->rb_right);
 		else if (base_reg < base_reg_tmp)
 			new = &((*new)->rb_left);
 	}

 	/* insert the node into the rbtree */
 	rb_link_node(&rbnode->node, parent, new);
 	rb_insert_color(&rbnode->node, root);

 	return 1;
 }

 #ifdef CONFIG_DEBUG_FS
 static int rbtree_show(struct seq_file *s, void *ignored)
 {
 	struct regmap *map = s->private;
 	struct regcache_rbtree_ctx *rbtree_ctx = map->cache;
 	struct regcache_rbtree_node *n;
 	struct rb_node *node;
 	unsigned int base, top;
 	int nodes = 0;
 	int registers = 0;
 	int this_registers, average;

 	map->lock(map);

 	for (node = rb_first(&rbtree_ctx->root); node != NULL;
 	     node = rb_next(node)) {
 		n = container_of(node, struct regcache_rbtree_node, node);

 		regcache_rbtree_get_base_top_reg(map, n, &base, &top);
 		this_registers = ((top - base) / map->reg_stride) + 1;
 		seq_printf(s, "%x-%x (%d)\n", base, top, this_registers);

 		nodes++;
 		registers += this_registers;
 	}

 	if (nodes)
 		average = registers / nodes;
 	else
 		average = 0;

 	seq_printf(s, "%d nodes, %d registers, average %d registers\n",
 		   nodes, registers, average);

 	map->unlock(map);

 	return 0;
 }

 static int rbtree_open(struct inode *inode, struct file *file)
 {
 	return single_open(file, rbtree_show, inode->i_private);
 }

 static const struct file_operations rbtree_fops = {
 	.open		= rbtree_open,
 	.read		= seq_read,
 	.llseek		= seq_lseek,
 	.release	= single_release,
 };

 static void rbtree_debugfs_init(struct regmap *map)
 {
 	debugfs_create_file("rbtree", 0400, map->debugfs, map, &rbtree_fops);
 }
 #else
 static void rbtree_debugfs_init(struct regmap *map)
 {
 }
 #endif

 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;

 	for (i = 0; i < map->num_reg_defaults; i++) {
 		ret = regcache_rbtree_write(map,
 					    map->reg_defaults[i].reg,
 					    map->reg_defaults[i].def);
 		if (ret)
 			goto err;
 	}

 	rbtree_debugfs_init(map);

 	return 0;

 err:
 	regcache_rbtree_exit(map);
 	return ret;
 }

 static int regcache_rbtree_exit(struct regmap *map)
 {
 	struct rb_node *next;
 	struct regcache_rbtree_ctx *rbtree_ctx;
 	struct regcache_rbtree_node *rbtree_node;

 	/* if we've already been called then just return */
 	rbtree_ctx = map->cache;
 	if (!rbtree_ctx)
 		return 0;

 	/* free up the rbtree */
 	next = rb_first(&rbtree_ctx->root);
 	while (next) {
 		rbtree_node = rb_entry(next, struct regcache_rbtree_node, node);
 		next = rb_next(&rbtree_node->node);
 		rb_erase(&rbtree_node->node, &rbtree_ctx->root);
 		kfree(rbtree_node->block);
 		kfree(rbtree_node);
 	}

 	/* release the resources */
 	kfree(map->cache);
 	map->cache = NULL;

 	return 0;
 }

 static int regcache_rbtree_read(struct regmap *map,
 				unsigned int reg, unsigned int *value)
 {
 	struct regcache_rbtree_node *rbnode;
 	unsigned int reg_tmp;

 	rbnode = regcache_rbtree_lookup(map, reg);
 	if (rbnode) {
 		reg_tmp = (reg - rbnode->base_reg) / map->reg_stride;
 		*value = regcache_rbtree_get_register(rbnode, reg_tmp,
 						      map->cache_word_size);
 	} else {
 		return -ENOENT;
 	}

 	return 0;
 }


 static int regcache_rbtree_insert_to_block(struct regcache_rbtree_node *rbnode,
 					   unsigned int pos, unsigned int reg,
 					   unsigned int value, unsigned int word_size)
 {
 	u8 *blk;

 	blk = krealloc(rbnode->block,
 		       (rbnode->blklen + 1) * word_size, GFP_KERNEL);
 	if (!blk)
 		return -ENOMEM;

 	/* insert the register value in the correct place in the rbnode block */
 	memmove(blk + (pos + 1) * word_size,
 		blk + pos * word_size,
 		(rbnode->blklen - pos) * word_size);

 	/* update the rbnode block, its size and the base register */
 	rbnode->block = blk;
 	rbnode->blklen++;
 	if (!pos)
 		rbnode->base_reg = reg;

 	regcache_rbtree_set_register(rbnode, pos, value, word_size);
 	return 0;
 }

 static int regcache_rbtree_write(struct regmap *map, unsigned int reg,
 				 unsigned int value)
 {
 	struct regcache_rbtree_ctx *rbtree_ctx;
 	struct regcache_rbtree_node *rbnode, *rbnode_tmp;
 	struct rb_node *node;
 	unsigned int val;
 	unsigned int reg_tmp;
 	unsigned int pos;
 	int i;
 	int ret;

 	rbtree_ctx = map->cache;
 	/* if we can't locate it in the cached rbnode we'll have
 	 * to traverse the rbtree looking for it.
 	 */
 	rbnode = regcache_rbtree_lookup(map, reg);
 	if (rbnode) {
 		reg_tmp = (reg - rbnode->base_reg) / map->reg_stride;
 		val = regcache_rbtree_get_register(rbnode, reg_tmp,
 						   map->cache_word_size);
 		if (val == value)
 			return 0;
 		regcache_rbtree_set_register(rbnode, reg_tmp, value,
 					     map->cache_word_size);
 	} else {
 		/* look for an adjacent register to the one we are about to add */
 		for (node = rb_first(&rbtree_ctx->root); node;
 		     node = rb_next(node)) {
 			rbnode_tmp = rb_entry(node, struct regcache_rbtree_node,
 					      node);
 			for (i = 0; i < rbnode_tmp->blklen; i++) {
 				reg_tmp = rbnode_tmp->base_reg +
 						(i * map->reg_stride);
 				if (abs(reg_tmp - reg) != map->reg_stride)
 					continue;
 				/* decide where in the block to place our register */
 				if (reg_tmp + map->reg_stride == reg)
 					pos = i + 1;
 				else
 					pos = i;
 				ret = regcache_rbtree_insert_to_block(rbnode_tmp, pos,
 								      reg, value,
 								      map->cache_word_size);
 				if (ret)
 					return ret;
 				rbtree_ctx->cached_rbnode = rbnode_tmp;
 				return 0;
 			}
 		}
 		/* we did not manage to find a place to insert it in an existing
 		 * block so create a new rbnode with a single register in its block.
 		 * This block will get populated further if any other adjacent
 		 * registers get modified in the future.
 		 */
 		rbnode = kzalloc(sizeof *rbnode, GFP_KERNEL);
 		if (!rbnode)
 			return -ENOMEM;
 		rbnode->blklen = 1;
 		rbnode->base_reg = reg;
 		rbnode->block = kmalloc(rbnode->blklen * map->cache_word_size,
 					GFP_KERNEL);
 		if (!rbnode->block) {
 			kfree(rbnode);
 			return -ENOMEM;
 		}
 		regcache_rbtree_set_register(rbnode, 0, value, map->cache_word_size);
 		regcache_rbtree_insert(map, &rbtree_ctx->root, rbnode);
 		rbtree_ctx->cached_rbnode = rbnode;
 	}

 	return 0;
 }

 static int regcache_rbtree_sync(struct regmap *map, unsigned int min,
 				unsigned int max)
 {
 	struct regcache_rbtree_ctx *rbtree_ctx;
 	struct rb_node *node;
 	struct regcache_rbtree_node *rbnode;
 	unsigned int regtmp;
 	unsigned int val;
 	int ret;
 	int i, base, end;

 	rbtree_ctx = map->cache;
 	for (node = rb_first(&rbtree_ctx->root); node; node = rb_next(node)) {
 		rbnode = rb_entry(node, struct regcache_rbtree_node, node);

 		if (rbnode->base_reg < min)
 			continue;
 		if (rbnode->base_reg > max)
 			break;
 		if (rbnode->base_reg + rbnode->blklen < min)
 			continue;

 		if (min > rbnode->base_reg)
 			base = min - rbnode->base_reg;
 		else
 			base = 0;

 		if (max < rbnode->base_reg + rbnode->blklen)
 			end = rbnode->base_reg + rbnode->blklen - max;
 		else
 			end = rbnode->blklen;

 		for (i = base; i < end; i++) {
 			regtmp = rbnode->base_reg + (i * map->reg_stride);
 			val = regcache_rbtree_get_register(rbnode, i,
 							   map->cache_word_size);

 			/* Is this the hardware default?  If so skip. */
 			ret = regcache_lookup_reg(map, regtmp);
 			if (ret >= 0 && val == map->reg_defaults[ret].def)
 				continue;

 			map->cache_bypass = 1;
 			ret = _regmap_write(map, regtmp, val);
 			map->cache_bypass = 0;
 			if (ret)
 				return ret;
 			dev_dbg(map->dev, "Synced register %#x, value %#x\n",
 				regtmp, val);
 		}
 	}

 	return 0;
 }

 struct regcache_ops regcache_rbtree_ops = {
 	.type = REGCACHE_RBTREE,
 	.name = "rbtree",
 	.init = regcache_rbtree_init,
 	.exit = regcache_rbtree_exit,
 	.read = regcache_rbtree_read,
 	.write = regcache_rbtree_write,
 	.sync = regcache_rbtree_sync
 };
	/*
	* Register cache access API - rbtree caching support
	*
	* Copyright 2011 Wolfson Microelectronics plc
	*
	* Author: Dimitris Papastamos <dp@opensource.wolfsonmicro.com>
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License version 2 as
	* published by the Free Software Foundation.
	*/

	#include <linux/slab.h>
	#include <linux/device.h>
	#include <linux/debugfs.h>
	#include <linux/rbtree.h>
	#include <linux/seq_file.h>

	#include "internal.h"

	static int regcache_rbtree_write(struct regmap *map, unsigned int reg,
	unsigned int value);
	static int regcache_rbtree_exit(struct regmap *map);

	struct regcache_rbtree_node {
	/* the actual rbtree node holding this block */
	struct rb_node node;
	/* base register handled by this block */
	unsigned int base_reg;
	/* block of adjacent registers */
	void *block;
	/* number of registers available in the block */
	unsigned int blklen;
	} __attribute__ ((packed));

	struct regcache_rbtree_ctx {
	struct rb_root root;
	struct regcache_rbtree_node *cached_rbnode;
	};

	static inline void regcache_rbtree_get_base_top_reg(
	struct regmap *map,
	struct regcache_rbtree_node *rbnode,
	unsigned int base, unsigned int top)
	{
	*base = rbnode->base_reg;
	top = rbnode->base_reg + ((rbnode->blklen - 1) map->reg_stride);
	}

	static unsigned int regcache_rbtree_get_register(
	struct regcache_rbtree_node *rbnode, unsigned int idx,
	unsigned int word_size)
	{
	return regcache_get_val(rbnode->block, idx, word_size);
	}

	static void regcache_rbtree_set_register(struct regcache_rbtree_node *rbnode,
	unsigned int idx, unsigned int val,
	unsigned int word_size)
	{
	regcache_set_val(rbnode->block, idx, val, word_size);
	}

	static struct regcache_rbtree_node regcache_rbtree_lookup(struct regmap map,
	unsigned int reg)
	{
	struct regcache_rbtree_ctx *rbtree_ctx = map->cache;
	struct rb_node *node;
	struct regcache_rbtree_node *rbnode;
	unsigned int base_reg, top_reg;

	rbnode = rbtree_ctx->cached_rbnode;
	if (rbnode) {
	regcache_rbtree_get_base_top_reg(map, rbnode, &base_reg,
	&top_reg);
	if (reg >= base_reg && reg <= top_reg)
	return rbnode;
	}

	node = rbtree_ctx->root.rb_node;
	while (node) {
	rbnode = container_of(node, struct regcache_rbtree_node, node);
	regcache_rbtree_get_base_top_reg(map, rbnode, &base_reg,
	&top_reg);
	if (reg >= base_reg && reg <= top_reg) {
	rbtree_ctx->cached_rbnode = rbnode;
	return rbnode;
	} else if (reg > top_reg) {
	node = node->rb_right;
	} else if (reg < base_reg) {
	node = node->rb_left;
	}
	}

	return NULL;
	}

	static int regcache_rbtree_insert(struct regmap map, struct rb_root root,
	struct regcache_rbtree_node *rbnode)
	{
	struct rb_node *new, parent;
	struct regcache_rbtree_node *rbnode_tmp;
	unsigned int base_reg_tmp, top_reg_tmp;
	unsigned int base_reg;

	parent = NULL;
	new = &root->rb_node;
	while (*new) {
	rbnode_tmp = container_of(*new, struct regcache_rbtree_node,
	node);
	/* base and top registers of the current rbnode */
	regcache_rbtree_get_base_top_reg(map, rbnode_tmp, &base_reg_tmp,
	&top_reg_tmp);
	/* base register of the rbnode to be added */
	base_reg = rbnode->base_reg;
	parent = *new;
	/* if this register has already been inserted, just return */
	if (base_reg >= base_reg_tmp &&
	base_reg <= top_reg_tmp)
	return 0;
	else if (base_reg > top_reg_tmp)
	new = &((*new)->rb_right);
	else if (base_reg < base_reg_tmp)
	new = &((*new)->rb_left);
	}

	/* insert the node into the rbtree */
	rb_link_node(&rbnode->node, parent, new);
	rb_insert_color(&rbnode->node, root);

	return 1;
	}

	#ifdef CONFIG_DEBUG_FS
	static int rbtree_show(struct seq_file s, void ignored)
	{
	struct regmap *map = s->private;
	struct regcache_rbtree_ctx *rbtree_ctx = map->cache;
	struct regcache_rbtree_node *n;
	struct rb_node *node;
	unsigned int base, top;
	int nodes = 0;
	int registers = 0;
	int this_registers, average;

	map->lock(map);

	for (node = rb_first(&rbtree_ctx->root); node != NULL;
	node = rb_next(node)) {
	n = container_of(node, struct regcache_rbtree_node, node);

	regcache_rbtree_get_base_top_reg(map, n, &base, &top);
	this_registers = ((top - base) / map->reg_stride) + 1;
	seq_printf(s, "%x-%x (%d)\n", base, top, this_registers);

	nodes++;
	registers += this_registers;
	}

	if (nodes)
	average = registers / nodes;
	else
	average = 0;

	seq_printf(s, "%d nodes, %d registers, average %d registers\n",
	nodes, registers, average);

	map->unlock(map);

	return 0;
	}

	static int rbtree_open(struct inode inode, struct file file)
	{
	return single_open(file, rbtree_show, inode->i_private);
	}

	static const struct file_operations rbtree_fops = {
	.open = rbtree_open,
	.read = seq_read,
	.llseek = seq_lseek,
	.release = single_release,
	};

	static void rbtree_debugfs_init(struct regmap *map)
	{
	debugfs_create_file("rbtree", 0400, map->debugfs, map, &rbtree_fops);
	}
	#else
	static void rbtree_debugfs_init(struct regmap *map)
	{
	}
	#endif

	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;

	for (i = 0; i < map->num_reg_defaults; i++) {
	ret = regcache_rbtree_write(map,
	map->reg_defaults[i].reg,
	map->reg_defaults[i].def);
	if (ret)
	goto err;
	}

	rbtree_debugfs_init(map);

	return 0;

	err:
	regcache_rbtree_exit(map);
	return ret;
	}

	static int regcache_rbtree_exit(struct regmap *map)
	{
	struct rb_node *next;
	struct regcache_rbtree_ctx *rbtree_ctx;
	struct regcache_rbtree_node *rbtree_node;

	/* if we've already been called then just return */
	rbtree_ctx = map->cache;
	if (!rbtree_ctx)
	return 0;

	/* free up the rbtree */
	next = rb_first(&rbtree_ctx->root);
	while (next) {
	rbtree_node = rb_entry(next, struct regcache_rbtree_node, node);
	next = rb_next(&rbtree_node->node);
	rb_erase(&rbtree_node->node, &rbtree_ctx->root);
	kfree(rbtree_node->block);
	kfree(rbtree_node);
	}

	/* release the resources */
	kfree(map->cache);
	map->cache = NULL;

	return 0;
	}

	static int regcache_rbtree_read(struct regmap *map,
	unsigned int reg, unsigned int *value)
	{
	struct regcache_rbtree_node *rbnode;
	unsigned int reg_tmp;

	rbnode = regcache_rbtree_lookup(map, reg);
	if (rbnode) {
	reg_tmp = (reg - rbnode->base_reg) / map->reg_stride;
	*value = regcache_rbtree_get_register(rbnode, reg_tmp,
	map->cache_word_size);
	} else {
	return -ENOENT;
	}

	return 0;
	}


	static int regcache_rbtree_insert_to_block(struct regcache_rbtree_node *rbnode,
	unsigned int pos, unsigned int reg,
	unsigned int value, unsigned int word_size)
	{
	u8 *blk;

	blk = krealloc(rbnode->block,
	(rbnode->blklen + 1) * word_size, GFP_KERNEL);
	if (!blk)
	return -ENOMEM;

	/* insert the register value in the correct place in the rbnode block */
	memmove(blk + (pos + 1) * word_size,
	blk + pos * word_size,
	(rbnode->blklen - pos) * word_size);

	/* update the rbnode block, its size and the base register */
	rbnode->block = blk;
	rbnode->blklen++;
	if (!pos)
	rbnode->base_reg = reg;

	regcache_rbtree_set_register(rbnode, pos, value, word_size);
	return 0;
	}

	static int regcache_rbtree_write(struct regmap *map, unsigned int reg,
	unsigned int value)
	{
	struct regcache_rbtree_ctx *rbtree_ctx;
	struct regcache_rbtree_node rbnode, rbnode_tmp;
	struct rb_node *node;
	unsigned int val;
	unsigned int reg_tmp;
	unsigned int pos;
	int i;
	int ret;

	rbtree_ctx = map->cache;
	/* if we can't locate it in the cached rbnode we'll have
	* to traverse the rbtree looking for it.
	*/
	rbnode = regcache_rbtree_lookup(map, reg);
	if (rbnode) {
	reg_tmp = (reg - rbnode->base_reg) / map->reg_stride;
	val = regcache_rbtree_get_register(rbnode, reg_tmp,
	map->cache_word_size);
	if (val == value)
	return 0;
	regcache_rbtree_set_register(rbnode, reg_tmp, value,
	map->cache_word_size);
	} else {
	/* look for an adjacent register to the one we are about to add */
	for (node = rb_first(&rbtree_ctx->root); node;
	node = rb_next(node)) {
	rbnode_tmp = rb_entry(node, struct regcache_rbtree_node,
	node);
	for (i = 0; i < rbnode_tmp->blklen; i++) {
	reg_tmp = rbnode_tmp->base_reg +
	(i * map->reg_stride);
	if (abs(reg_tmp - reg) != map->reg_stride)
	continue;
	/* decide where in the block to place our register */
	if (reg_tmp + map->reg_stride == reg)
	pos = i + 1;
	else
	pos = i;
	ret = regcache_rbtree_insert_to_block(rbnode_tmp, pos,
	reg, value,
	map->cache_word_size);
	if (ret)
	return ret;
	rbtree_ctx->cached_rbnode = rbnode_tmp;
	return 0;
	}
	}
	/* we did not manage to find a place to insert it in an existing
	* block so create a new rbnode with a single register in its block.
	* This block will get populated further if any other adjacent
	* registers get modified in the future.
	*/
	rbnode = kzalloc(sizeof *rbnode, GFP_KERNEL);
	if (!rbnode)
	return -ENOMEM;
	rbnode->blklen = 1;
	rbnode->base_reg = reg;
	rbnode->block = kmalloc(rbnode->blklen * map->cache_word_size,
	GFP_KERNEL);
	if (!rbnode->block) {
	kfree(rbnode);
	return -ENOMEM;
	}
	regcache_rbtree_set_register(rbnode, 0, value, map->cache_word_size);
	regcache_rbtree_insert(map, &rbtree_ctx->root, rbnode);
	rbtree_ctx->cached_rbnode = rbnode;
	}

	return 0;
	}

	static int regcache_rbtree_sync(struct regmap *map, unsigned int min,
	unsigned int max)
	{
	struct regcache_rbtree_ctx *rbtree_ctx;
	struct rb_node *node;
	struct regcache_rbtree_node *rbnode;
	unsigned int regtmp;
	unsigned int val;
	int ret;
	int i, base, end;

	rbtree_ctx = map->cache;
	for (node = rb_first(&rbtree_ctx->root); node; node = rb_next(node)) {
	rbnode = rb_entry(node, struct regcache_rbtree_node, node);

	if (rbnode->base_reg < min)
	continue;
	if (rbnode->base_reg > max)
	break;
	if (rbnode->base_reg + rbnode->blklen < min)
	continue;

	if (min > rbnode->base_reg)
	base = min - rbnode->base_reg;
	else
	base = 0;

	if (max < rbnode->base_reg + rbnode->blklen)
	end = rbnode->base_reg + rbnode->blklen - max;
	else
	end = rbnode->blklen;

	for (i = base; i < end; i++) {
	regtmp = rbnode->base_reg + (i * map->reg_stride);
	val = regcache_rbtree_get_register(rbnode, i,
	map->cache_word_size);

	/* Is this the hardware default? If so skip. */
	ret = regcache_lookup_reg(map, regtmp);
	if (ret >= 0 && val == map->reg_defaults[ret].def)
	continue;

	map->cache_bypass = 1;
	ret = _regmap_write(map, regtmp, val);
	map->cache_bypass = 0;
	if (ret)
	return ret;
	dev_dbg(map->dev, "Synced register %#x, value %#x\n",
	regtmp, val);
	}
	}

	return 0;
	}

	struct regcache_ops regcache_rbtree_ops = {
	.type = REGCACHE_RBTREE,
	.name = "rbtree",
	.init = regcache_rbtree_init,
	.exit = regcache_rbtree_exit,
	.read = regcache_rbtree_read,
	.write = regcache_rbtree_write,
	.sync = regcache_rbtree_sync
	};