Date:   Wed, 21 Feb 2018 17:31:14 +0200
From:   Daniel Baluta <daniel.baluta@...il.com>
To:     Pierre Bourdon <delroth@...gle.com>
Cc:     Jonathan Cameron <jic23@...nel.org>,
        Hartmut Knaack <knaack.h@....de>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        linux-iio@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] iio: light: add driver for bh1730fvc chips

Hi Pierre,

Few comments inline:

On Wed, Feb 21, 2018 at 2:55 PM, Pierre Bourdon <delroth@...gle.com> wrote:
> Ambient light sensor that supports visible light and IR measurements and
> configurable gain/integration time.
>

Can you have a quick look to existing ROHM light sensor support.
Perhaps your sensor
is similar enough with existing code.

I'm talking about:

drivers/iio/light/{bh1750.c  bh1780.c }

> Signed-off-by: Pierre Bourdon <delroth@...gle.com>
> ---
>  .../devicetree/bindings/iio/light/bh1730.txt  |  15 +
>  drivers/iio/light/Kconfig                     |  10 +
>  drivers/iio/light/Makefile                    |   1 +
>  drivers/iio/light/bh1730.c                    | 429 ++++++++++++++++++
>  4 files changed, 455 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/iio/light/bh1730.txt
>  create mode 100644 drivers/iio/light/bh1730.c
>
> diff --git a/Documentation/devicetree/bindings/iio/light/bh1730.txt b/Documentation/devicetree/bindings/iio/light/bh1730.txt
> new file mode 100644
> index 000000000000..6b38c4010647
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iio/light/bh1730.txt
> @@ -0,0 +1,15 @@
> +* ROHM BH1730FVC ambient light sensor
> +
> +http://www.rohm.com/web/global/products/-/product/BH1730FVC
> +
> +Required properties:
> +
> +  - compatible : should be "rohm,bh1730fvc"
> +  - reg : the I2C address of the sensor
> +
> +Example:
> +
> +bh1730fvc@29 {
> +       compatible = "rohm,bh1730fvc";
> +       reg = <0x29>;
> +};

Usually the devicetree binding part should be sent as a separate patch
 with device-tree mailing list and maintainer at CC.

Use ./scripts/get_maintainer.pl to find the exact emails.

Mind that you should sent a patchseries:

1/2 - driver code
2/2 - documentation

> diff --git a/drivers/iio/light/Kconfig b/drivers/iio/light/Kconfig
> index 93fd421b10d7..286a7f78762b 100644
> --- a/drivers/iio/light/Kconfig
> +++ b/drivers/iio/light/Kconfig
> @@ -63,6 +63,16 @@ config APDS9960
>           To compile this driver as a module, choose M here: the
>           module will be called apds9960
>
> +config BH1730
> +       tristate "ROHM BH1730 ambient light sensor"
> +       depends on I2C
> +       help
> +        Say Y here to build support for the ROHM BH1730FVC ambient
> +        light sensor.
> +
> +        To compile this driver as a module, choose M here: the module will
> +        be called bh1730.
> +
>  config BH1750
>         tristate "ROHM BH1750 ambient light sensor"
>         depends on I2C
> diff --git a/drivers/iio/light/Makefile b/drivers/iio/light/Makefile
> index f714067a7816..eb9010a10536 100644
> --- a/drivers/iio/light/Makefile
> +++ b/drivers/iio/light/Makefile
> @@ -9,6 +9,7 @@ obj-$(CONFIG_ADJD_S311)         += adjd_s311.o
>  obj-$(CONFIG_AL3320A)          += al3320a.o
>  obj-$(CONFIG_APDS9300)         += apds9300.o
>  obj-$(CONFIG_APDS9960)         += apds9960.o
> +obj-$(CONFIG_BH1730)           += bh1730.o
>  obj-$(CONFIG_BH1750)           += bh1750.o
>  obj-$(CONFIG_BH1780)           += bh1780.o
>  obj-$(CONFIG_CM32181)          += cm32181.o
> diff --git a/drivers/iio/light/bh1730.c b/drivers/iio/light/bh1730.c
> new file mode 100644
> index 000000000000..6912aaa3295b
> --- /dev/null
> +++ b/drivers/iio/light/bh1730.c
> @@ -0,0 +1,429 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * ROHM BH1730 ambient light sensor driver
> + *
> + * Copyright (c) 2018 Google, Inc.
> + * Author: Pierre Bourdon <delroth@...gle.com>
> + *
> + * Based on a previous non-iio BH1730FVC driver:
> + * Copyright (C) 2012 Samsung Electronics. All rights reserved.
> + * Author: Won Huh <won.huh@...sung.com>
> + *
> + * Data sheets:
> + *  http://www.rohm.com/web/global/datasheet/BH1730FVC/bh1730fvc-e
> + */
> +
> +#include <linux/delay.h>
> +#include <linux/i2c.h>
> +#include <linux/iio/iio.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/time.h>
> +
> +#define BH1730_CMD_BIT BIT(7)
> +
> +#define BH1730_REG_CONTROL     0x00
> +#define BH1730_REG_TIMING      0x01
> +#define BH1730_REG_INTERRUPT   0x02
> +#define BH1730_REG_THLLOW      0x03
> +#define BH1730_REG_THLHIGH     0x04
> +#define BH1730_REG_THHLOW      0x05
> +#define BH1730_REG_THHHIGH     0x06
> +#define BH1730_REG_GAIN                0x07
> +#define BH1730_REG_ID          0x12
> +#define BH1730_REG_DATA0LOW    0x14
> +#define BH1730_REG_DATA0HIGH   0x15
> +#define BH1730_REG_DATA1LOW    0x16
> +#define BH1730_REG_DATA1HIGH   0x17
> +
> +#define BH1730_CONTROL_POWER_ON                BIT(0)
> +#define BH1730_CONTROL_MEASURE         BIT(1)
> +
> +#define BH1730_INTERNAL_CLOCK_NS       2800ULL
> +
> +#define BH1730_DEFAULT_INTEG_MS                150
> +
> +enum bh1730_gain {
> +       BH1730_GAIN_1X = 0,
> +       BH1730_GAIN_2X,
> +       BH1730_GAIN_64X,
> +       BH1730_GAIN_128X,
> +};
> +
> +struct bh1730_data {
> +       struct i2c_client *client;
> +       enum bh1730_gain gain;
> +       int itime;
> +};
> +
> +static int bh1730_read_word(struct bh1730_data *bh1730, u8 reg)
> +{
> +       int ret = i2c_smbus_read_word_data(bh1730->client,
> +                                          BH1730_CMD_BIT | reg);
> +       if (ret < 0)
> +               dev_err(&bh1730->client->dev,
> +                       "i2c read failed error %d, register %01x\n",
> +                       ret, reg);
> +       return ret;
> +}
> +
> +static int bh1730_write(struct bh1730_data *bh1730, u8 reg, u8 val)
> +{
> +       int ret = i2c_smbus_write_byte_data(bh1730->client,
> +                                           BH1730_CMD_BIT | reg,
> +                                           val);
> +       if (ret < 0)
> +               dev_err(&bh1730->client->dev,
> +                       "i2c write failed error %d, register %01x\n",
> +                       ret, reg);
> +       return ret;
> +}
> +
> +static int gain_setting_to_multiplier(enum bh1730_gain gain)
> +{
> +       switch (gain) {
> +       case BH1730_GAIN_1X:
> +               return 1;
> +       case BH1730_GAIN_2X:
> +               return 2;
> +       case BH1730_GAIN_64X:
> +               return 64;
> +       case BH1730_GAIN_128X:
> +               return 128;
> +       default:
> +               return -1;
> +       }
> +}
> +
> +static int bh1730_gain_multiplier(struct bh1730_data *bh1730)
> +{
> +       int multiplier = gain_setting_to_multiplier(bh1730->gain);
> +
> +       if (multiplier < 0) {
> +               dev_warn(&bh1730->client->dev,
> +                        "invalid gain multiplier settings: %d\n",
> +                        bh1730->gain);
> +               bh1730->gain = BH1730_GAIN_1X;
> +               multiplier = 1;
> +       }
> +
> +       return multiplier;
> +}
> +
> +static u64 bh1730_itime_ns(struct bh1730_data *bh1730)
> +{
> +       return BH1730_INTERNAL_CLOCK_NS * 964 * (256 - bh1730->itime);
> +}
> +
> +static int bh1730_set_gain(struct bh1730_data *bh1730, enum bh1730_gain gain)
> +{
> +       int ret = bh1730_write(bh1730, BH1730_REG_GAIN, gain);
> +
> +       if (ret < 0)
> +               return ret;
> +
> +       bh1730->gain = gain;
> +       return 0;
> +}
> +
> +static int bh1730_set_integration_time_ms(struct bh1730_data *bh1730,
> +                                         int time_ms)
> +{
> +       int ret;
> +       u64 time_ns = time_ms * (u64)NSEC_PER_MSEC;
> +       u64 itime_step_ns = BH1730_INTERNAL_CLOCK_NS * 964;
> +       int itime = 256 - (int)DIV_ROUND_CLOSEST_ULL(time_ns, itime_step_ns);
> +
> +       /* ITIME == 0 is reserved for manual integration mode. */
> +       if (itime <= 0 || itime > 255) {
> +               dev_warn(&bh1730->client->dev,
> +                        "integration time out of range: %dms\n", time_ms);
> +               return -ERANGE;
> +       }
> +
> +       ret = bh1730_write(bh1730, BH1730_REG_TIMING, itime);
> +       if (ret < 0)
> +               return ret;
> +
> +       bh1730->itime = itime;
> +       return 0;
> +}
> +
> +static void bh1730_wait_for_next_measurement(struct bh1730_data *bh1730)
> +{
> +       ndelay(bh1730_itime_ns(bh1730) + BH1730_INTERNAL_CLOCK_NS * 714);
> +}
> +
> +static int bh1730_adjust_gain(struct bh1730_data *bh1730)
> +{
> +       int visible, ir, highest, ret, i;
> +
> +       visible = bh1730_read_word(bh1730, BH1730_REG_DATA0LOW);
> +       if (visible < 0)
> +               return visible;
> +
> +       ir = bh1730_read_word(bh1730, BH1730_REG_DATA1LOW);
> +       if (ir < 0)
> +               return ir;
> +
> +       highest = max(visible, ir);
> +
> +       /*
> +        * If the read value is being clamped, assume the worst and go to the
> +        * lowest possible gain. The alternative is doing multiple
> +        * recalibrations, which would be slower and have the same effect.
> +        */
> +       if (highest == USHRT_MAX)
> +               highest *= 128;
> +       else
> +               highest = (highest * 128) / bh1730_gain_multiplier(bh1730);
> +
> +       /*
> +        * Find the lowest gain multiplier which puts the measured values
> +        * above 1024. This threshold is chosen to match the gap between 2X
> +        * multiplier and 64X (next available) while keeping some margin.
> +        */
> +       for (i = BH1730_GAIN_1X; i < BH1730_GAIN_128X; ++i) {
> +               int adj = highest * gain_setting_to_multiplier(i) / 128;
> +
> +               if (adj >= 1024)
> +                       break;
> +       }
> +
> +       if (i != bh1730->gain) {
> +               ret = bh1730_set_gain(bh1730, i);
> +               if (ret < 0)
> +                       return ret;
> +
> +               bh1730_wait_for_next_measurement(bh1730);
> +       }
> +       return 0;
> +}
> +
> +static s64 bh1730_get_millilux(struct bh1730_data *bh1730)
> +{
> +       int visible, ir, visible_coef, ir_coef;
> +       u64 itime_us = bh1730_itime_ns(bh1730) / NSEC_PER_USEC;
> +       u64 millilux;
> +
> +       visible = bh1730_read_word(bh1730, BH1730_REG_DATA0LOW);
> +       if (visible < 0)
> +               return visible;
> +
> +       ir = bh1730_read_word(bh1730, BH1730_REG_DATA1LOW);
> +       if (ir < 0)
> +               return ir;
> +
> +       if (ir * 1000 / visible < 500) {
> +               visible_coef = 5002;
> +               ir_coef = 7502;
> +       } else if (ir * 1000 / visible < 754) {
> +               visible_coef = 2250;
> +               ir_coef = 2000;
> +       } else if (ir * 1000 / visible < 1029) {
> +               visible_coef = 1999;
> +               ir_coef = 1667;
> +       } else if (ir * 1000 / visible < 1373) {
> +               visible_coef = 885;
> +               ir_coef = 583;
> +       } else if (ir * 1000 / visible < 1879) {
> +               visible_coef = 309;
> +               ir_coef = 165;
> +       } else {
> +               return 0;
> +       }
> +
> +       millilux = (u64)USEC_PER_MSEC * (visible_coef * visible - ir_coef * ir);
> +       millilux /= bh1730_gain_multiplier(bh1730);
> +       millilux *= 103;
> +       millilux /= itime_us;
> +       return millilux;
> +}
> +
> +static int bh1730_power_on(struct bh1730_data *bh1730)
> +{
> +       int ret;
> +       int control =
> +               BH1730_CONTROL_POWER_ON |
> +               BH1730_CONTROL_MEASURE;
> +
> +       ret = bh1730_write(bh1730, BH1730_REG_CONTROL, control);
> +       if (ret < 0)
> +               return ret;

Directly return bh1730_write , remove ret and control. Similar with power_off.

> +       return 0;
> +}
> +
> +static int bh1730_set_defaults(struct bh1730_data *bh1730)
> +{
> +       int ret;
> +
> +       ret = bh1730_set_gain(bh1730, BH1730_GAIN_1X);
> +       if (ret < 0)
> +               return ret;
> +
> +       ret = bh1730_set_integration_time_ms(bh1730, BH1730_DEFAULT_INTEG_MS);
> +       if (ret < 0)
> +               return ret;
> +
> +       bh1730_wait_for_next_measurement(bh1730);
> +       return 0;
> +}
> +
> +static int bh1730_power_off(struct bh1730_data *bh1730)
> +{
> +       return bh1730_write(bh1730, BH1730_REG_CONTROL, 0);
> +}
> +
> +static int bh1730_read_raw(struct iio_dev *indio_dev,
> +                          struct iio_chan_spec const *chan,
> +                          int *val, int *val2, long mask)
> +{
> +       struct bh1730_data *bh1730 = iio_priv(indio_dev);
> +       int ret;
> +       s64 millilux;
> +
> +       ret = bh1730_adjust_gain(bh1730);
> +       if (ret < 0)
> +               return ret;
> +
> +       switch (mask) {
> +       case IIO_CHAN_INFO_PROCESSED:
> +               millilux = bh1730_get_millilux(bh1730);
> +               if (millilux < 0)
> +                       return millilux;
> +               *val = millilux / 1000;
> +               *val2 = (millilux % 1000) * 1000;
> +               return IIO_VAL_INT_PLUS_MICRO;
> +       case IIO_CHAN_INFO_RAW:
> +               switch (chan->channel2) {
> +               case IIO_MOD_LIGHT_CLEAR:
> +                       ret = bh1730_read_word(bh1730, BH1730_REG_DATA0LOW);
> +                       if (ret < 0)
> +                               return ret;
> +                       *val = ret;
> +                       return IIO_VAL_INT;
> +               case IIO_MOD_LIGHT_IR:
> +                       ret = bh1730_read_word(bh1730, BH1730_REG_DATA1LOW);
> +                       if (ret < 0)
> +                               return ret;
> +                       *val = ret;
> +                       return IIO_VAL_INT;
> +               default:
> +                       return -EINVAL;
> +               }
> +       case IIO_CHAN_INFO_SCALE:
> +               *val = bh1730_gain_multiplier(bh1730);
> +               return IIO_VAL_INT;
> +       default:
> +               return -EINVAL;
> +       }
> +}
> +
> +static const struct iio_info bh1730_info = {
> +       .read_raw = bh1730_read_raw,
> +};
> +
> +static const struct iio_chan_spec bh1730_channels[] = {
> +       {
> +               .type = IIO_LIGHT,
> +               .modified = 1,
> +               .channel2 = IIO_MOD_LIGHT_BOTH,
> +               .info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),
> +       },
> +       {
> +               .type = IIO_LIGHT,
> +               .modified = 1,
> +               .channel2 = IIO_MOD_LIGHT_CLEAR,
> +               .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
> +                                     BIT(IIO_CHAN_INFO_SCALE),
> +       },
> +       {
> +               .type = IIO_LIGHT,
> +               .modified = 1,
> +               .channel2 = IIO_MOD_LIGHT_IR,
> +               .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
> +                                     BIT(IIO_CHAN_INFO_SCALE),
> +       },
> +};
> +
> +static int bh1730_probe(struct i2c_client *client,
> +                       const struct i2c_device_id *id)
> +{
> +       struct bh1730_data *bh1730;
> +       struct i2c_adapter *adapter = to_i2c_adapter(client->dev.parent);
> +       struct iio_dev *indio_dev;
> +       int ret;
> +
> +       if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE))
> +               return -EIO;
> +
> +       indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*bh1730));
> +       if (!indio_dev)
> +               return -ENOMEM;
> +
> +       bh1730 = iio_priv(indio_dev);
> +       bh1730->client = client;
> +       i2c_set_clientdata(client, indio_dev);
> +
> +       ret = bh1730_power_on(bh1730);
> +       if (ret < 0)
> +               return ret;
> +
> +       ret = bh1730_set_defaults(bh1730);
> +       if (ret < 0)
> +               return ret;
> +
> +       indio_dev->dev.parent = &client->dev;
> +       indio_dev->info = &bh1730_info;
> +       indio_dev->name = "bh1730";
> +       indio_dev->channels = bh1730_channels;
> +       indio_dev->num_channels = ARRAY_SIZE(bh1730_channels);
> +       indio_dev->modes = INDIO_DIRECT_MODE;
> +
> +       ret = iio_device_register(indio_dev);
> +       if (ret)
> +               goto out_power_off;
> +       return 0;
> +
> +out_power_off:
> +       bh1730_power_off(bh1730);
> +       return ret;
> +}
> +
> +static int bh1730_remove(struct i2c_client *client)
> +{
> +       struct iio_dev *indio_dev = i2c_get_clientdata(client);
> +       struct bh1730_data *bh1730 = iio_priv(indio_dev);
> +
> +       iio_device_unregister(indio_dev);
> +       return bh1730_power_off(bh1730);
> +}
> +
> +static const struct i2c_device_id bh1730_id[] = {
> +       { "bh1730", 0 },
> +       {},
> +};
> +MODULE_DEVICE_TABLE(i2c, bh1730_id);
> +
> +#ifdef CONFIG_OF
> +static const struct of_device_id of_bh1730_match[] = {
> +       { .compatible = "rohm,bh1730fvc" },
> +       {},
> +};
> +MODULE_DEVICE_TABLE(of, of_bh1730_match);
> +#endif
> +
> +static struct i2c_driver bh1730_driver = {
> +       .probe = bh1730_probe,

I wonder if you can use the probe_new API here.

e.g

https://patchwork.kernel.org/patch/9395073/
> +       .remove = bh1730_remove,
> +       .id_table = bh1730_id,
> +       .driver = {
> +               .name = "bh1730",
> +               .of_match_table = of_match_ptr(of_bh1730_match),
> +       },
> +};
> +module_i2c_driver(bh1730_driver);
> +
> +MODULE_AUTHOR("Pierre Bourdon <delroth@...gle.com>");
> +MODULE_DESCRIPTION("ROHM BH1730FVC driver");
> +MODULE_LICENSE("GPL v2");
>

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