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Date: Mon, 18 Jul 2011 12:38:14 +0200
Message-ID: <s5hsjq3kh61.wl%tiwai@suse.de>
From: Takashi Iwai <tiwai@suse.de>
To: Mark Brown <broonie@opensource.wolfsonmicro.com>
Cc: Greg KH <greg@kroah.com>, Grant Likely <grant@secretlab.ca>,
        Jean Delvare <khali@linux-fr.org>, Ben Dooks <ben-linux@fluff.org>,
        Dimitris Papastamos <dp@opensource.wolfsonmicro.com>,
        Liam Girdwood <lrg@ti.com>, Samuel Oritz <sameo@linux.intel.com>,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/4] regmap: Add generic non-memory mapped register access API
In-Reply-To: <1310983663-6404-1-git-send-email-broonie@opensource.wolfsonmicro.com>
References: <20110718100444.GD423@opensource.wolfsonmicro.com>
	<1310983663-6404-1-git-send-email-broonie@opensource.wolfsonmicro.com>
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At Mon, 18 Jul 2011 19:07:40 +0900,
Mark Brown wrote:
> 
> +static int _regmap_raw_write(struct regmap *map, unsigned int reg,
> +			     const void *val, size_t val_len)
> +{
> +	void *buf;
> +	int ret = -ENOTSUPP;
> +	size_t len;
> +
> +	map->format.format_reg(map->work_buf, reg);
> +
> +	/* Try to do a gather write if we can */
> +	if (map->bus->gather_write)
> +		ret = map->bus->gather_write(map->dev, map->work_buf,
> +					     map->format.reg_bytes,
> +					     val, val_len);
> +
> +	/* Otherwise fall back on linearising by hand. */
> +	if (ret == -ENOTSUPP) {
> +		len = map->format.reg_bytes + val_len;
> +		buf = kmalloc(len, GFP_KERNEL);
> +		if (!buf)
> +			return -ENOMEM;
> +
> +		memcpy(buf, map->work_buf, map->format.reg_bytes);
> +		memcpy(buf + map->format.reg_bytes, val, val_len);
> +		ret = map->bus->write(map->dev, buf, len);
> +
> +		kfree(buf);

In most cases, val = map->work_buf + map->format.reg_bytes.
How about a bit optimization?

	if (ret == -ENOTSUPP) {
		len = map->format.reg_bytes + val_len;
		if (val == map->work_buf + map->format.reg_bytes)
			ret = map->bus->write(map->dev, map->work_buf, len);
		else {
			buf = kmalloc(len, GFP_KERNEL);
			if (!buf)
				return -ENOMEM;

			memcpy(buf, map->work_buf, map->format.reg_bytes);
			memcpy(buf + map->format.reg_bytes, val, val_len);
			ret = map->bus->write(map->dev, buf, len);

			kfree(buf);
		}
	}


thanks,

Takashi