Message-ID: <553D376B.8000301@kernel.org>
Date:	Sun, 26 Apr 2015 20:07:23 +0100
From:	Jonathan Cameron <jic23@...nel.org>
To:	tduszyns@...il.com
CC:	knaack.h@....de, lars@...afoo.de, pmeerw@...erw.net,
	linux-kernel@...r.kernel.org, linux-iio@...r.kernel.org
Subject: Re: [PATCH v2] iio: light: add support for ROHM BH1710/BH1715/BH1721/BH1750/BH1751
 ambient light sensors

On 26/04/15 19:41, tduszyns@...il.com wrote:
> On Sun, Apr 26, 2015 at 05:50:02PM +0100, Jonathan Cameron wrote:
>> On 25/04/15 15:18, Tomasz Duszynski wrote:
>>> Add support for ROHM BH1710/BH1715/BH1721/BH1750/BH1751 ambient light
>>> sensors.
>>>
>>> Signed-off-by: Tomasz Duszynski <tduszyns@...il.com>
>> On query on why we no longer have a resume function... Otherwise
>> looks pretty good to me (couple of other comments inline.)
>>
>> Jonathan
>>> ---
>>>  Changes in v2:
>>>  	- Store chip-dependent values in chip_info structure
>>> 	- Add bh1750_remove to power down chip (necessary for BH1721)
>>> 	- Use one time mode for chips that have support for that
>>> 	- Use IIO_LIGHT instead of IIO_INTENSITY for channel type
>>>
>>>  drivers/iio/light/Kconfig  |  10 ++
>>>  drivers/iio/light/Makefile |   1 +
>>>  drivers/iio/light/bh1750.c | 329 +++++++++++++++++++++++++++++++++++++++++++++
>>>  3 files changed, 340 insertions(+)
>>>  create mode 100644 drivers/iio/light/bh1750.c
>>>
>>> diff --git a/drivers/iio/light/Kconfig b/drivers/iio/light/Kconfig
>>> index 5a3237b..ebc578a 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 "ROHM BH1750 ambient light sensor"
>>> +	depends on I2C
>>> +	help
>>> +	 Say Y here to build support for the ROHM 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..3b051ef
>>> --- /dev/null
>>> +++ b/drivers/iio/light/bh1750.c
>>> @@ -0,0 +1,329 @@
>>> +/*
>>> + * 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_ONT_TIME_H_RES_MODE	0x20 /* 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 {
>>> +	u16 mtreg_min;
>>> +	u16 mtreg_max;
>>> +	u16 mtreg_default;
>>> +	int mtreg_to_usec;
>>> +	int mtreg_to_scale;
>>> +
>>> +	/*
>>> +	 * For BH1710/BH1721 all possible integration time values won't fit
>>> +	 * into one page so displaying is limited to every second one.
>>> +	 * Note, that user can still write proper values which were not
>>> +	 * listed.
>>> +	 */
>>> +	int inc;
>>> +
>>> +	u16 int_time_low_mask;
>>> +	u16 int_time_high_mask;
>>> +};
>>> +
>>> +struct bh1750_data {
>>> +	struct i2c_client *client;
>>> +	struct mutex lock;
>>> +	const struct bh1750_chip_info *chip_info;
>>> +	u16 mtreg;
>>> +};
>>> +
>> Small point, but I'd have this array just after the structure definition
>> to allow that to act as the documentation for which variable is which
>> in here. Otherwise I'd be inclined to suggest the use of c99 assignments
>> to make this easy to check (uses a lot more lines!)
>>
> OK.
>> Given there looks to be a high level of compatibility in here
>> (i.e. BH1715, BH1750 and BM1751 are identical?) you could use
>> just one entry and have that reflected in the i2c device id table.
>> It isn't a large enough set of repeats that I actually care either
>> way however!
> OK.
>>> +static const struct bh1750_chip_info bh1750_chip_info_tbl[] = {
>>> +	[BH1710] = { 140, 1022, 300, 400,  4000,  2, 0x001F, 0x03E0 },
>>> +	[BH1715] = { 31,  254,  69,  1740, 17391, 1, 0x001F, 0x00E0 },
>>> +	[BH1721] = { 140, 1020, 300, 400,  4000,  2, 0x0010, 0x03E0 },
>>> +	[BH1750] = { 31,  254,  69,  1740, 17391, 1, 0x001F, 0x00E0 },
>>> +	[BH1751] = { 31,  254,  69,  1740, 17391, 1, 0x001F, 0x00E0 }
>>> +};
>>> +
>>> +static int bh1750_change_int_time(struct bh1750_data *data, int usec)
>>> +{
>>> +	int ret;
>>> +	u16 val;
>>> +	u8 regval;
>>> +	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;
>>> +
>>> +	ret = i2c_smbus_write_byte(data->client, BH1750_POWER_DOWN);
>>> +	if (ret < 0)
>>> +		return ret;
>>> +
>>> +	regval = (val & chip_info->int_time_high_mask) >> 5;
>>> +	ret = i2c_smbus_write_byte(data->client,
>>> +				   BH1750_CHANGE_INT_TIME_H_BIT | regval);
>>> +	if (ret < 0)
>>> +		return ret;
>>> +
>>> +	regval = val & chip_info->int_time_low_mask;
>>> +	ret = i2c_smbus_write_byte(data->client,
>>> +				   BH1750_CHANGE_INT_TIME_L_BIT | regval);
>>> +	if (ret < 0)
>>> +		return ret;
>>> +
>>> +	data->mtreg = val;
>>> +
>>> +	return 0;
>>> +}
>>> +
>>> +static int bh1750_read(struct bh1750_data *data, int *val)
>>> +{
>>> +	int ret;
>>> +	u16 result;
>>> +	const struct bh1750_chip_info *chip_info = data->chip_info;
>>> +	unsigned long delay = chip_info->mtreg_to_usec * data->mtreg;
>>> +
>>> +	ret = i2c_smbus_write_byte(data->client, BH1750_ONT_TIME_H_RES_MODE);
>>> +	if (ret < 0)
>>> +		return ret;
>>> +
>>> +	usleep_range(delay + 15000, delay + 40000);
>>> +
>>> +	ret = i2c_master_recv(data->client, (char *)&result, 2);
>>> +	if (ret < 0)
>>> +		return ret;
>>> +
>>> +	*val = swab16(result);
>>> +
>>> +	return 0;
>>> +}
>>> +
>>> +static int bh1750_read_raw(struct iio_dev *indio_dev,
>>> +			   struct iio_chan_spec const *chan,
>>> +			   int *val, int *val2, long mask)
>>> +{
>>> +	int ret, tmp;
>>> +	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_LIGHT:
>>> +			mutex_lock(&data->lock);
>>> +			ret = bh1750_read(data, val);
>>> +			mutex_unlock(&data->lock);
>>> +			if (ret < 0)
>>> +				return ret;
>>> +
>>> +			return IIO_VAL_INT;
>>> +		default:
>>> +			return -EINVAL;
>>> +		}
>>> +	case IIO_CHAN_INFO_SCALE:
>>> +		tmp = chip_info->mtreg_to_scale * data->mtreg;
>>> +		*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;
>>> +	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;
>>> +
>>> +	for (i = chip_info->mtreg_min; i <= chip_info->mtreg_max; i += chip_info->inc)
>>> +		len += scnprintf(buf + len, PAGE_SIZE - len, "0.%06d ",
>>> +				 chip_info->mtreg_to_usec * i);
>>> +
>>> +	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_LIGHT,
>>> +		.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 = &bh1750_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 iio_device_register(indio_dev);
>>> +}
>>> +
>>> +static int bh1750_remove(struct i2c_client *client)
>>> +{
>>> +	struct iio_dev *indio_dev = i2c_get_clientdata(client);
>>> +	struct bh1750_data *data = iio_priv(indio_dev);
>>> +
>>> +	iio_device_unregister(indio_dev);
>>> +
>>> +	mutex_lock(&data->lock);
>>> +	i2c_smbus_write_byte(client, BH1750_POWER_DOWN);
>>> +	mutex_unlock(&data->lock);
>>> +
>>> +	return 0;
>>> +}
>>> +
>>> +#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;
>>> +}
>> silly question.... When does it make sense to have a suspend but
>> no resume?
>>
>> You had one in V1...
> Yes, because in V1 all sensors were configured to work in continous mode.
>>
>> Either the chip is always powering up before and then down after reading,
>> in which case what is the suspend for?  Or... It's not and you probably
>> need that resume.
> Right, as long as sensor works in one time mode it obviously doesn't make
> sense to have either suspend or resume.
> 
> The problem is with BH1721 which only supports continous mode. And if
> one wants to change from continous to power down request for that
> has to be sent. That's the reason why I left suspend.
Ah. So it sort of ignores the attempt to move to the one time read
mode in the read function.
> 
> Resume is not necessary as this is already done by bh1750_read()
> next time user reads new data. Note that one time measurement command
> causes BH1721 to enter continous auto mode.
Thanks for the explanation.  Could you add a few comments to this
effect (one here and one in the read function) so that future readers
of the code don't get confused (i.e. me when I've forgotten all about this!)
>>> +
>>> +static SIMPLE_DEV_PM_OPS(bh1750_pm_ops, bh1750_suspend, NULL);
>>> +#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,
>>> +	},
>>> +	.probe = bh1750_probe,
>>> +	.remove = bh1750_remove,
>>> +	.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");
>>> --
>>> 2.3.6
>>>
>>
> Thanks for review!
> 

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