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From:   "Pierre Bourdon (delroth)" <delroth@google.com>
Date:   Wed, 21 Feb 2018 17:15:55 +0100
Message-ID: <CANEr7oX_V1vchZA+J2ia5GkZf6jZiVN0ByWK2G4jTp0EFXphqg@mail.gmail.com>
Subject: Re: [PATCH] iio: light: add driver for bh1730fvc chips
To:     Daniel Baluta <daniel.baluta@gmail.com>
Cc:     Jonathan Cameron <jic23@kernel.org>,
        Hartmut Knaack <knaack.h@gmx.de>,
        Lars-Peter Clausen <lars@metafoo.de>,
        Peter Meerwald-Stadler <pmeerw@pmeerw.net>,
        linux-iio@vger.kernel.org,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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Sender: linux-kernel-owner@vger.kernel.org
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Hi Daniel,

On Wed, Feb 21, 2018 at 4:31 PM, Daniel Baluta <daniel.baluta@gmail.com> wrote:
> On Wed, Feb 21, 2018 at 2:55 PM, Pierre Bourdon <delroth@google.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 }

bh1750 does things sufficiently different in its protocol that the
amount of common code would be fairly small. Unlike bh1730/bh1780 it's
not fully SMBus compatible for example.

bh1780 could probably be implemented as a subset of bh1730. It's
basically a simplified bh1730 with less knobs. But there is still a
significant amount of differences that make common code difficult to
extract. For example, bh1780 reads lux values directly from the chip,
whereas bh1730 has two raw channels that need to be combined in
software to get a processed lux value. It could be done, but my gut
feeling is that writing a "HAL" for this is going to make things more
complicated, not simpler.

My experience in this domain is close to zero, so I'm completely open
to giving it a try if you think merging these two makes sense.

>> Signed-off-by: Pierre Bourdon <delroth@google.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

Will do. Should the of_match_table in the driver code be part of 1/2
(driver) or 2/2 (dt-bindings)?

I'll send a v2 with this + the other changes you've suggested.

Thanks!

>> 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@google.com>
>> + *
>> + * Based on a previous non-iio BH1730FVC driver:
>> + * Copyright (C) 2012 Samsung Electronics. All rights reserved.
>> + * Author: Won Huh <won.huh@samsung.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@google.com>");
>> +MODULE_DESCRIPTION("ROHM BH1730FVC driver");
>> +MODULE_LICENSE("GPL v2");
>>

-- 
Pierre Bourdon (delroth@)