linux-kernel - Re: [PATCH 1/8] regmap: Add generic non-memory mapped register access API

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Date:	Fri, 01 Jul 2011 01:22:41 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	Mark Brown <broonie@...nsource.wolfsonmicro.com>
Cc:	linux-kernel@...r.kernel.org,
	Dimitris Papastamos <dp@...nsource.wolfsonmicro.com>,
	Samuel Ortiz <sameo@...ux.intel.com>,
	Liam Girdwood <lrg@...com>,
	Lars-Peter Clausen <lars@...afoo.de>,
	Graeme Gregory <gg@...mlogic.co.uk>
Subject: Re: [PATCH 1/8] regmap: Add generic non-memory mapped register
 access API

On Wed, 2011-06-22 at 19:45 +0100, Mark Brown wrote:
[...]
> --- /dev/null
> +++ b/drivers/regmap/regmap.c
[...]
> +static void regmap_format_4_12_write(struct regmap *map,
> +				     unsigned int reg, unsigned int val)
> +{
> +	u16 *out = map->work_buf;

__be16 *out

> +	*out = cpu_to_be16((reg << 12) | val);
> +}
> +
> +static void regmap_format_7_9_write(struct regmap *map,
> +				    unsigned int reg, unsigned int val)
> +{
> +	u16 *out = map->work_buf;

__be16 *out

> +	*out = cpu_to_be16((reg << 9) | val);
> +}
> +
> +static void regmap_format_8(void *buf, unsigned int val)
> +{
> +	u8 *b = buf;
> +
> +	b[0] = val;
> +}
> +
> +static void regmap_format_16(void *buf, unsigned int val)
> +{
> +	u16 *b = buf;

__be16 *b

> +	b[0] = cpu_to_be16(val);
> +}
> +
> +static unsigned int regmap_parse_8(void *buf)
> +{
> +	u8 *b = buf;
> +
> +	return b[0];
> +}
> +
> +static unsigned int regmap_parse_16(void *buf)
> +{
> +	u16 *b = buf;

__be16 *b

> +	b[0] = be16_to_cpu(b[0]);
> +
> +	return b[0];

The assignment doesn't seem to be necessary and will irritate sparse,
so:

	return be16_to_cpu(b[0]);

> +}
> +
> +/**
> + * remap_init: Initialise register map

Missing 'g' in 'regmap_init'.  And the first line's format must be:

   regmap_init() - Initialise register map

(The other functions all have this problem as well.)

> + * dev: Device that will be interacted with
> + * config: Configuration for register map

Missing '@' before the parameter names.

[...]
> +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);
[...]

If I understand correctly, this is usually called by _regmap_write() and
val is already at the appropriate offset in work_buf.  Is it not worth
avoiding the allocation in that case?

General comments:

- All the functions must be called in process context, but this isn't
documented.
- I think this could go in lib or drivers/base rather than in a new
directory.  The specific support for I2C and SPI would go in their
existing directories.

Ben.

-- 
Ben Hutchings
If the facts do not conform to your theory, they must be disposed of.

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