Date:	Wed, 22 Apr 2015 10:49:21 +0200 (CEST)
From:	Peter Meerwald <pmeerw@...erw.net>
To:	Tomasz Duszynski <tduszyns@...il.com>
cc:	jic23@...nel.org, knaack.h@....de, lars@...afoo.de,
	linux-kernel@...r.kernel.org, linux-iio@...r.kernel.org
Subject: Re: [PATCH] iio: light: add support for ROHM BH1710/BH1715/BH1721/BH1750/BH1751
 ambient light sensors

On Tue, 21 Apr 2015, Tomasz Duszynski wrote:

> Add support for ROHM BH1710/BH1715/BH1721/BH1750/BH1751 ambient light
> sensors.

nice, some comments inline
 
> Signed-off-by: Tomasz Duszynski <tduszyns@...il.com>
> ---
>  drivers/iio/light/Kconfig  |  10 ++
>  drivers/iio/light/Makefile |   1 +
>  drivers/iio/light/bh1750.c | 322 +++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 333 insertions(+)
>  create mode 100644 drivers/iio/light/bh1750.c
> 
> diff --git a/drivers/iio/light/Kconfig b/drivers/iio/light/Kconfig
> index 5a3237b..9fb79ca 100644
> --- a/drivers/iio/light/Kconfig
> +++ b/drivers/iio/light/Kconfig
> @@ -37,6 +37,16 @@ config APDS9300
>  	 To compile this driver as a module, choose M here: the
>  	 module will be called apds9300.
>  
> +config BH1750
> +	tristate "BH1750 ambient light sensor"
> +	depends on I2C
> +	help
> +	 Say Y here to build support for the BH1710, BH1715, BH1721,
> +	 BH1750, BH1751 ambient light sensors.
> +
> +	 To compile this driver as a module, choose M here: the module will
> +	 be called bh1750.
> +
>  config CM32181
>  	depends on I2C
>  	tristate "CM32181 driver"
> diff --git a/drivers/iio/light/Makefile b/drivers/iio/light/Makefile
> index 74656c1..1a13184 100644
> --- a/drivers/iio/light/Makefile
> +++ b/drivers/iio/light/Makefile
> @@ -6,6 +6,7 @@
>  obj-$(CONFIG_ADJD_S311)		+= adjd_s311.o
>  obj-$(CONFIG_AL3320A)		+= al3320a.o
>  obj-$(CONFIG_APDS9300)		+= apds9300.o
> +obj-$(CONFIG_BH1750)		+= bh1750.o
>  obj-$(CONFIG_CM32181)		+= cm32181.o
>  obj-$(CONFIG_CM36651)		+= cm36651.o
>  obj-$(CONFIG_GP2AP020A00F)	+= gp2ap020a00f.o
> diff --git a/drivers/iio/light/bh1750.c b/drivers/iio/light/bh1750.c
> new file mode 100644
> index 0000000..83b5413
> --- /dev/null
> +++ b/drivers/iio/light/bh1750.c
> @@ -0,0 +1,322 @@
> +/*
> + * ROHM BH1710/BH1715/BH1721/BH1750/BH1751 ambient light sensor driver
> + *
> + * Copyright (c) Tomasz Duszynski <tduszyns@...il.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.
> + *
> + * Data sheets:
> + *  http://rohmfs.rohm.com/en/products/databook/datasheet/ic/sensor/light/bh1710fvc-e.pdf
> + *  http://rohmfs.rohm.com/en/products/databook/datasheet/ic/sensor/light/bh1715fvc-e.pdf
> + *  http://rohmfs.rohm.com/en/products/databook/datasheet/ic/sensor/light/bh1721fvc-e.pdf
> + *  http://rohmfs.rohm.com/en/products/databook/datasheet/ic/sensor/light/bh1750fvi-e.pdf
> + *  http://rohmfs.rohm.com/en/products/databook/datasheet/ic/sensor/light/bh1751fvi-e.pdf
> + *
> + * 7-bit I2C slave addresses:
> + *  0x23 (ADDR pin low)
> + *  0x5C (ADDR pin high)
> + *
> + */
> +
> +#include <linux/delay.h>
> +#include <linux/i2c.h>
> +#include <linux/iio/iio.h>
> +#include <linux/iio/sysfs.h>
> +#include <linux/module.h>
> +
> +#define BH1750_POWER_DOWN		0x00
> +#define BH1750_H_RES_MODE		0x10 /* auto-mode for BH1721 */
> +#define BH1750_CHANGE_INT_TIME_H_BIT	0x40
> +#define BH1750_CHANGE_INT_TIME_L_BIT	0x60
> +
> +enum {
> +	BH1710,
> +	BH1715,
> +	BH1721,
> +	BH1750,
> +	BH1751
> +};
> +
> +struct bh1750_chip_info {
> +	int id;

why is the id stored in chip_info?
the point of the chip_info table is to avoid switch blocks in the driver; 
I suggest to move remaining chip-dependent values to the table and drop 
the id

> +	int mtreg_min;
> +	int mtreg_max;
> +	int mtreg_default;

u16, these are values stored in an u16 register

> +	int mtreg_to_usec;
> +	int mtreg_to_scale;
> +};
> +
> +struct bh1750_data {
> +	struct i2c_client *client;
> +	struct mutex lock;
> +	const struct bh1750_chip_info *chip_info;
> +	u16 mtreg;
> +};
> +
> +static const struct bh1750_chip_info chip_info_tbl[] = {
> +	[BH1710] = { BH1710, 140, 1022, 300, 400,  4000 },
> +	[BH1715] = { BH1715, 31,  254,  69,  1740, 17391 },
> +	[BH1721] = { BH1721, 140, 1020, 300, 400,  4000 },
> +	[BH1750] = { BH1750, 31,  254,  69,  1740, 17391 },
> +	[BH1751] = { BH1751, 31,  254,  69,  1740, 17391 }
> +};
> +
> +static int bh1750_change_int_time(struct bh1750_data *data, int usec)
> +{
> +	int ret, val;
> +	u8 low = 0, high = 0;

initialization not needed, low/high should always be set

> +	const struct bh1750_chip_info *chip_info = data->chip_info;
> +
> +	if ((usec % chip_info->mtreg_to_usec) != 0)
> +		return -EINVAL;
> +
> +	val = usec / chip_info->mtreg_to_usec;
> +	if (val < chip_info->mtreg_min || val > chip_info->mtreg_max)
> +		return -EINVAL;
> +
> +	switch (chip_info->id) {
> +	case BH1710:
> +		low = val & 0x001F;
> +		high = (val & 0x03E0) >> 5;
> +		break;
> +	case BH1721:
> +		low = val & 0x0010;
> +		high = (val & 0x03E0) >> 5;

break missing?

> +	case BH1715:
> +	case BH1750:
> +	case BH1751:
> +		low = val & 0x001F;
> +		high = (val & 0x00E0) >> 5;
> +		break;
> +	}
> +
> +	ret = i2c_smbus_write_byte(data->client, BH1750_POWER_DOWN);
> +	if (ret < 0)
> +		return ret;
> +
> +	ret = i2c_smbus_write_byte(data->client,
> +				   BH1750_CHANGE_INT_TIME_H_BIT | high);
> +	if (ret < 0)
> +		return ret;
> +
> +	ret = i2c_smbus_write_byte(data->client,
> +				   BH1750_CHANGE_INT_TIME_L_BIT | low);
> +	if (ret < 0)
> +		return ret;
> +
> +	data->mtreg = val;
> +
> +	return i2c_smbus_write_byte(data->client, BH1750_H_RES_MODE);
> +}
> +
> +static int bh1750_read_raw(struct iio_dev *indio_dev,
> +			   struct iio_chan_spec const *chan,
> +			   int *val, int *val2, long mask)
> +{
> +	u16 result;
> +	int ret, tmp;
> +	unsigned long delay;
> +	struct bh1750_data *data = iio_priv(indio_dev);
> +	const struct bh1750_chip_info *chip_info = data->chip_info;
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_RAW:
> +		switch (chan->type) {
> +		case IIO_INTENSITY:
> +			delay = chip_info->mtreg_to_usec * data->mtreg;
> +			mutex_lock(&data->lock);
> +			usleep_range(delay, delay + 20000);

the driver uses continuous mode and there is no data-ready flag

why not using one time mode?, I think this would better fit in what other 
drivers are doing

> +			ret = i2c_master_recv(data->client,
> +					      (char *)&result, 2);

almost all drivers use i2c_smbus_read_word_xxx() -- is there a reason not 
to?

> +			mutex_unlock(&data->lock);
> +			if (ret < 0)
> +				return ret;
> +
> +			*val = swab16(result);
> +			return IIO_VAL_INT;
> +		default:
> +			return -EINVAL;
> +		}
> +	case IIO_CHAN_INFO_SCALE:
> +		tmp = chip_info->mtreg_to_scale * data->mtreg;

use the variable delay as above; the same computation is done in every 
switch case

> +		*val = tmp / 1000000;
> +		*val2 = tmp % 1000000;
> +		return IIO_VAL_INT_PLUS_MICRO;
> +	case IIO_CHAN_INFO_INT_TIME:
> +		*val = 0;
> +		*val2 = chip_info->mtreg_to_usec * data->mtreg;
> +		return IIO_VAL_INT_PLUS_MICRO;
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +static int bh1750_write_raw(struct iio_dev *indio_dev,
> +			    struct iio_chan_spec const *chan,
> +			    int val, int val2, long mask)
> +{
> +	int ret;
> +	struct bh1750_data *data = iio_priv(indio_dev);
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_INT_TIME:
> +		if (val != 0)
> +			return -EINVAL;
> +
> +		mutex_lock(&data->lock);
> +		ret = bh1750_change_int_time(data, val2);
> +		mutex_unlock(&data->lock);
> +		return ret;
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +static ssize_t bh1750_show_int_time_available(struct device *dev,
> +		struct device_attribute *attr, char *buf)
> +{
> +	int i, inc;
> +	size_t len = 0;
> +	struct bh1750_data *data = iio_priv(dev_to_iio_dev(dev));
> +	const struct bh1750_chip_info *chip_info = data->chip_info;
> +
> +	switch (chip_info->id) {
> +	case BH1710:
> +	case BH1721:
> +		/* All values won't fit into one page, so display every
> +		 * second one. By doing so step size is increased
> +		 * from 0.4ms to 0.8ms.*/

multi-line comment style?;
missing space before */

> +		inc = 2;
> +		break;
> +	default:
> +		inc = 1;
> +		break;
> +	}
> +
> +	for (i = chip_info->mtreg_min; i <= chip_info->mtreg_max; i += inc)
> +		len += scnprintf(buf + len, PAGE_SIZE - len, "0.%06d ",
> +				 i * chip_info->mtreg_to_usec);
> +
> +	buf[len - 1] = '\n';
> +
> +	return len;
> +}
> +
> +static IIO_DEV_ATTR_INT_TIME_AVAIL(bh1750_show_int_time_available);
> +
> +static struct attribute *bh1750_attributes[] = {
> +	&iio_dev_attr_integration_time_available.dev_attr.attr,
> +	NULL,
> +};
> +
> +static struct attribute_group bh1750_attribute_group = {
> +	.attrs = bh1750_attributes,
> +};
> +
> +static const struct iio_info bh1750_info = {
> +	.driver_module = THIS_MODULE,
> +	.attrs = &bh1750_attribute_group,
> +	.read_raw = bh1750_read_raw,
> +	.write_raw = bh1750_write_raw,
> +};
> +
> +static const struct iio_chan_spec bh1750_channels[] = {
> +	{
> +		.type = IIO_INTENSITY,
> +		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
> +				      BIT(IIO_CHAN_INFO_SCALE) |
> +				      BIT(IIO_CHAN_INFO_INT_TIME)
> +	}
> +};
> +
> +static int bh1750_probe(struct i2c_client *client,
> +			const struct i2c_device_id *id)
> +{
> +	int ret, usec;
> +	struct bh1750_data *data;
> +	struct iio_dev *indio_dev;
> +
> +	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C |
> +				I2C_FUNC_SMBUS_WRITE_BYTE))
> +		return -ENODEV;
> +
> +	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
> +	if (!indio_dev)
> +		return -ENOMEM;
> +
> +	data = iio_priv(indio_dev);
> +	i2c_set_clientdata(client, indio_dev);
> +	data->client = client;
> +	data->chip_info = &chip_info_tbl[id->driver_data];
> +
> +	usec = data->chip_info->mtreg_to_usec * data->chip_info->mtreg_default;
> +	ret = bh1750_change_int_time(data, usec);
> +	if (ret < 0)
> +		return ret;
> +
> +	mutex_init(&data->lock);
> +	indio_dev->dev.parent = &client->dev;
> +	indio_dev->info = &bh1750_info;
> +	indio_dev->name = id->name;
> +	indio_dev->channels = bh1750_channels;
> +	indio_dev->num_channels = ARRAY_SIZE(bh1750_channels);
> +	indio_dev->modes = INDIO_DIRECT_MODE;
> +
> +	return devm_iio_device_register(&client->dev, indio_dev);

chip should probably be powered down if this fails; or use one-time mode

> +}
> +
> +#ifdef CONFIG_PM_SLEEP
> +static int bh1750_suspend(struct device *dev)
> +{
> +	int ret;
> +	struct bh1750_data *data =
> +		iio_priv(i2c_get_clientdata(to_i2c_client(dev)));
> +
> +	mutex_lock(&data->lock);
> +	ret = i2c_smbus_write_byte(data->client, BH1750_POWER_DOWN);
> +	mutex_unlock(&data->lock);
> +
> +	return ret;
> +}
> +
> +static int bh1750_resume(struct device *dev)
> +{
> +	struct bh1750_data *data =
> +		iio_priv(i2c_get_clientdata(to_i2c_client(dev)));
> +
> +	return i2c_smbus_write_byte(data->client, BH1750_H_RES_MODE);
> +}
> +
> +static SIMPLE_DEV_PM_OPS(bh1750_pm_ops, bh1750_suspend, bh1750_resume);
> +#define BH1750_PM_OPS (&bh1750_pm_ops)
> +#else
> +#define BH1750_PM_OPS NULL
> +#endif
> +
> +static const struct i2c_device_id bh1750_id[] = {
> +	{ "bh1710", BH1710 },
> +	{ "bh1715", BH1715 },
> +	{ "bh1721", BH1721 },
> +	{ "bh1750", BH1750 },
> +	{ "bh1751", BH1751 },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(i2c, bh1750_id);
> +
> +static struct i2c_driver bh1750_driver = {
> +	.driver = {
> +		.name = "bh1750",
> +		.owner = THIS_MODULE,
> +		.pm = BH1750_PM_OPS,
> +	},

.remove to power down

> +	.probe = bh1750_probe,
> +	.id_table = bh1750_id,
> +
> +};
> +module_i2c_driver(bh1750_driver);
> +
> +MODULE_AUTHOR("Tomasz Duszynski <tduszyns@...il.com>");
> +MODULE_DESCRIPTION("ROHM BH1710/BH1715/BH1721/BH1750/BH1751 als driver");
> +MODULE_LICENSE("GPL v2");
> 

-- 

Peter Meerwald
+43-664-2444418 (mobile)
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