Date:	Sat, 30 Aug 2014 11:00:06 +0100
From:	Jonathan Cameron <jic23@...nel.org>
To:	Hartmut Knaack <knaack.h@....de>,
	Daniel Baluta <daniel.baluta@...el.com>,
	linux-iio@...r.kernel.org, pmeerw@...erw.net
CC:	linux-kernel@...r.kernel.org, Tsechih_Lin@...s.com
Subject: Re: [PATCH v3] iio: Add Dyna-Image AL3320A ambient light sensor driver

On 27/08/14 09:49, Hartmut Knaack wrote:
> Daniel Baluta schrieb:
>> Minimal implementation. This driver provides raw illuminance readings.
>>
>> This is based on drivers/hwmon/al3320.c (*) driver from msm tree written
>> by Tsechih Lin <Tsechih_Lin@...s.com>
>>
>> * https://android.googlesource.com/kernel/msm.git
>>
>> Signed-off-by: Daniel Baluta <daniel.baluta@...el.com>
> Hi, I think you should protect your write_raw with a mutex. 
Either that or drop the local store of the value and read it back from
the device (assuming you can!).  That way everything becomes nice an
atomic.  It's a rather narrow race, but Hartmut is correct in pointing it
out.

Few comments inline, mostly about my pet peeve: wrapper functions that don't
do much.  Note I'm not that fussed if you really really want to keep them ;)

Otherwise, looks good.

J
>Other minor comments inline.
>> ---
>> Changes since v2: (reported by Peter Meerwald)
>> 	* removed definition of DATA_HIGH and SW_RESET as they are not used
>> 	* added a comment to al3320a_get_adc_value() function
>> 	* added thresholds on TODO list
>> 	* small stye fixes
>>
>> Changes since v1: (reported by Peter Meerwald)
>> 	* used u8 instead of int for passing gain and mean_time
>> 	* used i2c_smbus_read_word_swapped instead of 2 x i2c_smbus_read_byte_data
>> 	* used devm_iio_device_register instead of iio_device_register
>> 	* small style fixes
>>
>>  drivers/iio/light/Kconfig   |  10 ++
>>  drivers/iio/light/Makefile  |   1 +
>>  drivers/iio/light/al3320a.c | 255 ++++++++++++++++++++++++++++++++++++++++++++
>>  3 files changed, 266 insertions(+)
>>  create mode 100644 drivers/iio/light/al3320a.c
>>
>> diff --git a/drivers/iio/light/Kconfig b/drivers/iio/light/Kconfig
>> index bf05ca5..5bea821 100644
>> --- a/drivers/iio/light/Kconfig
>> +++ b/drivers/iio/light/Kconfig
>> @@ -17,6 +17,16 @@ config ADJD_S311
>>  	 This driver can also be built as a module.  If so, the module
>>  	 will be called adjd_s311.
>>
>> +config AL3320A
>> +	tristate "AL3320A ambient light sensor"
>> +	depends on I2C
>> +	help
>> +	 Say Y here if you want to build a driver for the Dyna Image AL3320A
>> +	 ambient light sensor.
>> +
>> +	 To compile this driver as a module, choose M here: the
>> +	 module will be called al3320a.
>> +
>>  config APDS9300
>>  	tristate "APDS9300 ambient light sensor"
>>  	depends on I2C
>> diff --git a/drivers/iio/light/Makefile b/drivers/iio/light/Makefile
>> index 8b8c09f..47877a3 100644
>> --- a/drivers/iio/light/Makefile
>> +++ b/drivers/iio/light/Makefile
>> @@ -4,6 +4,7 @@
>>
>>  # When adding new entries keep the list in alphabetical order
>>  obj-$(CONFIG_ADJD_S311)		+= adjd_s311.o
>> +obj-$(CONFIG_AL3320A)		+= al3320a.o
>>  obj-$(CONFIG_APDS9300)		+= apds9300.o
>>  obj-$(CONFIG_CM32181)		+= cm32181.o
>>  obj-$(CONFIG_CM36651)		+= cm36651.o
>> diff --git a/drivers/iio/light/al3320a.c b/drivers/iio/light/al3320a.c
>> new file mode 100644
>> index 0000000..28fc8b0
>> --- /dev/null
>> +++ b/drivers/iio/light/al3320a.c
>> @@ -0,0 +1,255 @@
>> +/*
>> + * AL3320A - Dyna Image Ambient Light Sensor
>> + *
>> + * Copyright (c) 2014, Intel Corporation.
>> + *
>> + * This file is subject to the terms and conditions of version 2 of
>> + * the GNU General Public License.  See the file COPYING in the main
>> + * directory of this archive for more details.
>> + *
>> + * IIO driver for AL3320A (7-bit I2C slave address 0x1C).
>> + *
>> + * TODO: interrupt support, thresholds
>> + *
>> + */
>> +
>> +#include <linux/module.h>
>> +#include <linux/init.h>
>> +#include <linux/i2c.h>
>> +
>> +#include <linux/iio/iio.h>
>> +#include <linux/iio/sysfs.h>
>> +
>> +#define AL3320A_DRV_NAME "al3320a"
>> +
>> +#define AL3320A_REG_CONFIG		0x00
>> +#define AL3320A_REG_STATUS		0x01
>> +#define AL3320A_REG_INT			0x02
>> +#define AL3320A_REG_WAIT		0x06
>> +#define AL3320A_REG_CONFIG_RANGE	0x07
>> +#define AL3320A_REG_PERSIST		0x08
>> +#define AL3320A_REG_MEAN_TIME		0x09
>> +#define AL3320A_REG_ADUMMY		0x0A
>> +#define AL3320A_REG_DATA_LOW		0x22
>> +
>> +#define AL3320A_REG_LOW_THRESH_LOW	0x30
>> +#define AL3320A_REG_LOW_THRESH_HIGH	0x31
>> +#define AL3320A_REG_HIGH_THRESH_LOW	0x32
>> +#define AL3320A_REG_HIGH_THRESH_HIGH	0x33
>> +
>> +#define AL3320A_CONFIG_DISABLE		0x00
>> +#define AL3320A_CONFIG_ENABLE		BIT(0)
>> +
>> +#define AL3320A_GAIN_SHIFT		1
>> +
>> +/* chip params default values */
>> +#define AL3320A_DEFAULT_MEAN_TIME	4
>> +#define AL3320A_DEFAULT_WAIT_TIME	0 /* no waiting */
>> +
>> +enum al3320a_range {
>> +	AL3320A_RANGE_1, /* 33.28K lux */
>> +	AL3320A_RANGE_2, /* 8.32K lux  */
>> +	AL3320A_RANGE_3, /* 2.08K lux  */
>> +	AL3320A_RANGE_4  /* 0.65K lux  */
>> +};
>> +
>> +static const int al3320a_scales[][2] = {
>> +	{0, 512000}, {0, 128000}, {0, 32000}, {0, 10000}
>> +};
>> +
>> +struct al3320a_data {
>> +	struct i2c_client *client;
>> +	u8 range;
>> +};
>> +
>> +static const struct iio_chan_spec al3320a_channels[] = {
>> +	{
>> +		.type	= IIO_LIGHT,
>> +		.info_mask_separate =
>> +			BIT(IIO_CHAN_INFO_RAW) |
>> +			BIT(IIO_CHAN_INFO_SCALE),
> I would indent it like this:
>
> +		.type = IIO_LIGHT,
> +		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
> +				      BIT(IIO_CHAN_INFO_SCALE),
>
>
>> +	}
>> +};
>> +
As commented below, you do have a lot of wrapper functions whose
function is pretty obvious from what is inside them that could just
be rolled into the call sites for a shorter, cleaner driver...
>> +static int al3320a_enable(struct al3320a_data *data)
>> +{
>> +	return i2c_smbus_write_byte_data(data->client, AL3320A_REG_CONFIG,
>> +					 AL3320A_CONFIG_ENABLE);
>> +}
>> +
>> +static int al3320a_disable(struct al3320a_data *data)
>> +{
>> +	return i2c_smbus_write_byte_data(data->client, AL3320A_REG_CONFIG,
>> +					 AL3320A_CONFIG_DISABLE);
>> +}
>> +
>> +static int al3320a_set_config_range(struct al3320a_data *data, u8 gain)
>> +{
>> +	int ret;
>> +
>> +	ret = i2c_smbus_write_byte_data(data->client, AL3320A_REG_CONFIG_RANGE,
>> +					 gain << AL3320A_GAIN_SHIFT);
> If you remove the whitespace before gain, you would get a perfect indentation.
>> +	if (ret >= 0)
> From the description: This executes the SMBus "write byte" protocol, returning negative errno else zero on success.
> So, checking for 0 is sufficient and fits better with your upper level functions.
>> +		data->range = gain;
>> +	return ret;
>> +}
>> +
>> +static int al3320a_set_mean_time(struct al3320a_data *data, u8 mean_time)
>> +{
>> +	return i2c_smbus_write_byte_data(data->client, AL3320A_REG_MEAN_TIME,
>> +					 mean_time);
>> +}
>> +
>> +static int al3320a_set_wait_time(struct al3320a_data *data, u8 wait_time)
>> +{
>> +	return i2c_smbus_write_byte_data(data->client, AL3320A_REG_WAIT,
>> +					 wait_time);
>> +}
>> +
>> +/**
>> + * al3320a_get_adc_value() - report raw ADC reading
>> + * @data - pointer to struct al3320a_data
>> + *
>> + * ALS ADC value is stored in two adjacent registers:
>> + *   - low byte of the channel output is stored at AL3320A_REG_DATA_LOW
>> + *   - high byte of channel output is stored at AL3320A_REG_DATA_LOW + 1.
>> + *
>> + * Return: positive raw ADC reading or negative error code.
>> + */
>> +static int al3320a_get_adc_value(struct al3320a_data *data)
>> +{
>> +	return i2c_smbus_read_word_swapped(data->client, AL3320A_REG_DATA_LOW);
I suppose the comment above almost justifies the trivial wrapper function.
Hmm.  Could just put the comment where the read line would be...
>> +}
>> +
>> +static int al3320a_init(struct al3320a_data *data)
>> +{
>> +	int ret;
>> +
>> +	/* power on */
>> +	ret = al3320a_enable(data);
>> +	if (ret)
>> +		return ret;
>> +
>> +	ret = al3320a_set_config_range(data, AL3320A_RANGE_3);
>> +	if (ret)
>> +		return ret;
>> +
>> +	ret = al3320a_set_mean_time(data, AL3320A_DEFAULT_MEAN_TIME);
>> +	if (ret)
>> +		return ret;
>> +
>> +	ret = al3320a_set_wait_time(data, AL3320A_DEFAULT_WAIT_TIME);
>> +	if (ret)
>> +		return ret;
>> +
>> +	return 0;
>> +}
>> +
>> +static int al3320a_read_raw(struct iio_dev *indio_dev,
>> +			    struct iio_chan_spec const *chan,
>> +			    int *val,
>> +			    int *val2,
>> +			    long mask)
> Since you don't put a parameter per line in other function, do the same here and save some lines ;-)
>> +{
>> +	struct al3320a_data *data = iio_priv(indio_dev);
>> +	int ret;
>> +
>> +	switch (mask) {
>> +	case IIO_CHAN_INFO_RAW:
>> +		ret = al3320a_get_adc_value(data);
>> +		if (ret < 0)
>> +			return ret;
>> +		*val = ret;
>> +		return IIO_VAL_INT;
>> +	case IIO_CHAN_INFO_SCALE:
>> +		*val = al3320a_scales[data->range][0];
>> +		*val2 = al3320a_scales[data->range][1];
>> +		return IIO_VAL_INT_PLUS_MICRO;
>> +	}
>> +	return -EINVAL;
>> +}
>> +
>> +static int al3320a_write_raw(struct iio_dev *indio_dev,
>> +			     struct iio_chan_spec const *chan,
>> +			     int val, int val2, long mask)
>> +{
>> +	struct al3320a_data *data = iio_priv(indio_dev);
>> +	int i;
>> +
>> +	switch (mask) {
>> +	case IIO_CHAN_INFO_SCALE:
>> +		for (i = 0; i < ARRAY_SIZE(al3320a_scales); i++) {
>> +			if (val == al3320a_scales[i][0] &&
>> +			    val2 == al3320a_scales[i][1])
>> +				return al3320a_set_config_range(data, i);
>> +		}
>> +		break;
>> +	}
>> +	return -EINVAL;
>> +}
Given that there is no way of knowing valid values without digging out
the datasheet or reading the code, you'll want an _available attribute
listing them.

>> +
>> +static const struct iio_info al3320a_info = {
>> +	.driver_module	= THIS_MODULE,
>> +	.read_raw	= al3320a_read_raw,
>> +	.write_raw	= al3320a_write_raw,
>> +};
>> +
>> +static int al3320a_probe(struct i2c_client *client,
>> +			 const struct i2c_device_id *id)
>> +{
>> +	struct al3320a_data *data;
>> +	struct iio_dev *indio_dev;
>> +	int ret;
>> +
>> +	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;
>> +
>> +	indio_dev->dev.parent = &client->dev;
>> +	indio_dev->info = &al3320a_info;
>> +	indio_dev->name = AL3320A_DRV_NAME;
>> +	indio_dev->channels = al3320a_channels;
>> +	indio_dev->num_channels = ARRAY_SIZE(al3320a_channels);
>> +	indio_dev->modes = INDIO_DIRECT_MODE;
>> +
>> +	ret = al3320a_init(data);
>> +	if (ret) {
>> +		dev_err(&client->dev, "al3320a chip init failed\n");
>> +		return ret;
>> +	}
>> +
>> +	return devm_iio_device_register(&client->dev, indio_dev);
>> +}
>> +
>> +static int al3320a_remove(struct i2c_client *client)
>> +{
>> +	struct iio_dev *indio_dev = i2c_get_clientdata(client);
>> +	struct al3320a_data *data = iio_priv(indio_dev);
>> +
>> +	return al3320a_disable(data);
slight personal preference would be to roll this up into a one liner.
        return al3320a_disable(iio_priv(i2c_get_clientdata(client)));
Or seeing as how trivial the disable function is just roll that in here.

In fact a few of the wrapper functions don't really have enough in them
to justify their existence.  Doesn't really matter though if you particularly
like the long winded option ;)
>> +}
>> +
>> +static const struct i2c_device_id al3320a_id[] = {
>> +	{"al3320a", 0},
>> +	{}
>> +};
>> +MODULE_DEVICE_TABLE(i2c, al3320a_id);
>> +
>> +static struct i2c_driver al3320a_driver = {
>> +	.driver = {
>> +		.name = AL3320A_DRV_NAME,
>> +	},
>> +	.probe		= al3320a_probe,
>> +	.remove		= al3320a_remove,
>> +	.id_table	= al3320a_id,
>> +};
>> +
>> +module_i2c_driver(al3320a_driver);
>> +
>> +MODULE_AUTHOR("Daniel Baluta <daniel.baluta@...el.com>");
>> +MODULE_DESCRIPTION("AL3320A Ambient Light Sensor driver");
>> +MODULE_LICENSE("GPL v2");
>
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