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Date:	Tue, 19 Jun 2007 16:58:46 +0530
From:	"Trilok Soni" <soni.trilok@...il.com>
To:	"Rodolfo Giometti" <giometti@...eenne.com>
Cc:	i2c@...sensors.org, linux-kernel@...r.kernel.org,
	"Andrew Morton" <akpm@...ux-foundation.org>
Subject: Re: [PATCH] I2C: TSL2550 support.

Hi Rodolfo,

On 6/19/07, Rodolfo Giometti <giometti@...eenne.com> wrote:
> Add support for Taos TSL2550 ambient light sensors.
> (http://www.taosinc.com/product_detail.asp?cateid=4&proid=18).
>
> Signed-off-by: Rodolfo Giometti <giometti@...ux.it>
> ---
>  drivers/i2c/chips/Kconfig   |   10 +
>  drivers/i2c/chips/Makefile  |    1 +
>  drivers/i2c/chips/tsl2550.c |  427 +++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 438 insertions(+), 0 deletions(-)
>  create mode 100644 drivers/i2c/chips/tsl2550.c
>
> diff --git a/drivers/i2c/chips/Kconfig b/drivers/i2c/chips/Kconfig
> index ea085a0..b59c013 100644
> --- a/drivers/i2c/chips/Kconfig
> +++ b/drivers/i2c/chips/Kconfig
> @@ -124,4 +124,14 @@ config SENSORS_MAX6875
>           This driver can also be built as a module.  If so, the module
>           will be called max6875.
>
> +config SENSORS_TSL2550
> +       tristate "Taos TSL2550 ambient light sensor"
> +       depends on I2C && EXPERIMENTAL
> +       help
> +         If you say yes here you get support for the Taos TSL2550
> +         ambient light sensor.
> +
> +         This driver can also be built as a module.  If so, the module
> +         will be called tsl2550.
> +
>  endmenu
> diff --git a/drivers/i2c/chips/Makefile b/drivers/i2c/chips/Makefile
> index 779868e..1ef6a04 100644
> --- a/drivers/i2c/chips/Makefile
> +++ b/drivers/i2c/chips/Makefile
> @@ -12,6 +12,7 @@ obj-$(CONFIG_SENSORS_PCF8574) += pcf8574.o
>  obj-$(CONFIG_SENSORS_PCF8591)  += pcf8591.o
>  obj-$(CONFIG_ISP1301_OMAP)     += isp1301_omap.o
>  obj-$(CONFIG_TPS65010)         += tps65010.o
> +obj-$(CONFIG_SENSORS_TSL2550)  += tsl2550.o
>
>  ifeq ($(CONFIG_I2C_DEBUG_CHIP),y)
>  EXTRA_CFLAGS += -DDEBUG
> diff --git a/drivers/i2c/chips/tsl2550.c b/drivers/i2c/chips/tsl2550.c
> new file mode 100644
> index 0000000..fd7f87c
> --- /dev/null
> +++ b/drivers/i2c/chips/tsl2550.c
> @@ -0,0 +1,427 @@
> +/*
> + *  tsl2550.c - Linux kernel modules for ambient light sensor
> + *
> + *  Copyright (C) 2007 Rodolfo Giometti <giometti@...ux.it>
> + *  Copyright (C) 2007 Eurotech S.p.A. <info@...otech.it>
> + *
> + *  This program is free software; you can redistribute it and/or modify
> + *  it under the terms of the GNU General Public License as published by
> + *  the Free Software Foundation; either version 2 of the License, or
> + *  (at your option) any later version.
> + *
> + *  This program is distributed in the hope that it will be useful,
> + *  but WITHOUT ANY WARRANTY; without even the implied warranty of
> + *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + *  GNU General Public License for more details.
> + *
> + *  You should have received a copy of the GNU General Public License
> + *  along with this program; if not, write to the Free Software
> + *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
> + */
> +
> +#include <linux/module.h>
> +#include <linux/init.h>
> +#include <linux/slab.h>
> +#include <linux/i2c.h>
> +#include <linux/mutex.h>
> +#include <linux/delay.h>
> +
> +#define TSL2550_DRV_NAME       "tsl2550"
> +#define DRIVER_VERSION         "1.1.0"
> +
> +/* --- Defines ------------------------------------------------------------- */
> +
> +#define TSL2550_POWER_DOWN             0x00
> +#define TSL2550_POWER_UP               0x03
> +#define TSL2550_STANDARD_RANGE         0x18
> +#define TSL2550_EXTENDED_RANGE         0x1d
> +#define TSL2550_READ_ADC0              0x43
> +#define TSL2550_READ_ADC1              0x83
> +
> +/* --- Structs ------------------------------------------------------------- */
> +
> +struct tsl2550_data {
> +       struct i2c_client *client;
> +       struct mutex update_lock;
> +
> +       unsigned int power_state : 1;
> +       unsigned int operating_mode : 1;
> +};
> +
> +/* --- Management functions ------------------------------------------------ */
> +
> +static int tsl2550_set_operating_mode(struct i2c_client *client, int mode)
> +{
> +       struct tsl2550_data *data = i2c_get_clientdata(client);
> +       int ret;
> +
> +       mode = !!mode;
> +       if (mode == data->operating_mode)
> +               return 0;
> +
> +       if (mode == 0)
> +               ret = i2c_smbus_write_byte(client, TSL2550_STANDARD_RANGE);
> +       else
> +               ret = i2c_smbus_write_byte(client, TSL2550_EXTENDED_RANGE);
> +
> +       data->operating_mode = mode;
> +
> +       return ret;
> +}
> +
> +static int tsl2550_set_power_state(struct i2c_client *client, int state)
> +{
> +       struct tsl2550_data *data = i2c_get_clientdata(client);
> +       int ret;
> +
> +       state = !!state;
> +       if (state == data->power_state)
> +               return 0;
> +
> +       if (state == 0)
> +               ret = i2c_smbus_write_byte(client, TSL2550_POWER_DOWN);
> +       else {
> +               ret = i2c_smbus_write_byte(client, TSL2550_POWER_UP);
> +
> +               /* On power up we should reset operating mode also... */
> +               tsl2550_set_operating_mode(client, data->operating_mode);
> +       }
> +
> +       data->power_state = state;
> +
> +       return ret;
> +}
> +
> +static int tsl2550_get_adc_value(struct i2c_client *client, int channel)
> +{
> +       u8 cmd = channel == 0 ? TSL2550_READ_ADC0 : TSL2550_READ_ADC1;
> +       unsigned long end;
> +       int loop = 0, ret = 0;
> +
> +       /* Read ADC channel waiting at most 400ms (see data sheet for further
> +         * info).
> +        * To avoid long busy wait we spin for few milliseconds then
> +        * start sleeping. */

multi-line comment block format is not correct. It should be

> +       /*
> +        * Read ADC channel waiting at most 400ms (see data sheet for further
> +        * info).
> +        * To avoid long busy wait we spin for few milliseconds then
> +        * start sleeping.
> +        */

please change it to other places in driver also.


> +       end = jiffies + msecs_to_jiffies(400);
> +       while (time_before(jiffies, end)) {
> +               i2c_smbus_write_byte(client, cmd);
> +
> +               if (loop++ < 5)
> +                       mdelay(1);
> +               else
> +                       msleep(1);
> +
> +               ret = i2c_smbus_read_byte(client);
> +               if (ret < 0)
> +                       return ret;
> +               else if (ret & 0x0080)
> +                       break;
> +       }
> +       if (!(ret & 0x0080))
> +               return -EIO;
> +       return ((u8) ret) & 0x7f;       /* remove the "valid" bit */
> +}
> +
> +/* --- LUX calculation ----------------------------------------------------- */
> +
> +#define        TSL2550_MAX_LUX         1846
> +
> +static const u8 ratio_lut[] = {
> +       100, 100, 100, 100, 100, 100, 100, 100,
> +       100, 100, 100, 100, 100, 100, 99, 99,
> +       99, 99, 99, 99, 99, 99, 99, 99,
> +       99, 99, 99, 98, 98, 98, 98, 98,
> +       98, 98, 97, 97, 97, 97, 97, 96,
> +       96, 96, 96, 95, 95, 95, 94, 94,
> +       93, 93, 93, 92, 92, 91, 91, 90,
> +       89, 89, 88, 87, 87, 86, 85, 84,
> +       83, 82, 81, 80, 79, 78, 77, 75,
> +       74, 73, 71, 69, 68, 66, 64, 62,
> +       60, 58, 56, 54, 52, 49, 47, 44,
> +       42, 41, 40, 40, 39, 39, 38, 38,
> +       37, 37, 37, 36, 36, 36, 35, 35,
> +       35, 35, 34, 34, 34, 34, 33, 33,
> +       33, 33, 32, 32, 32, 32, 32, 31,
> +       31, 31, 31, 31, 30, 30, 30, 30,
> +       30,
> +};
> +
> +static const u16 count_lut[] = {
> +       0, 1, 2, 3, 4, 5, 6, 7,
> +       8, 9, 10, 11, 12, 13, 14, 15,
> +       16, 18, 20, 22, 24, 26, 28, 30,
> +       32, 34, 36, 38, 40, 42, 44, 46,
> +       49, 53, 57, 61, 65, 69, 73, 77,
> +       81, 85, 89, 93, 97, 101, 105, 109,
> +       115, 123, 131, 139, 147, 155, 163, 171,
> +       179, 187, 195, 203, 211, 219, 227, 235,
> +       247, 263, 279, 295, 311, 327, 343, 359,
> +       375,  391, 407, 423, 439, 455, 471, 487,
> +       511, 543, 575, 607, 639, 671, 703, 735,
> +       767, 799, 831, 863, 895, 927, 959, 991,
> +       1039, 1103, 1167, 1231, 1295, 1359, 1423, 1487,
> +       1551, 1615, 1679, 1743, 1807, 1871, 1935, 1999,
> +       2095, 2223, 2351, 2479, 2607, 2735, 2863, 2991,
> +       3119, 3247, 3375, 3503, 3631, 3759, 3887, 4015
> +};
> +
> +/* This function is described into Taos TSL2550 Designer's Notebook
> + * pages 2, 3 */
> +static int tsl2550_calculate_lux(u8 ch0, u8 ch1)
> +{
> +       unsigned int lux;
> +
> +       /* Look up count from channel values */
> +       u16 c0 = count_lut[ch0];
> +       u16 c1 = count_lut[ch1];
> +
> +       /* Calculate ratio.
> +        * Note: the "128" is a scaling factor */
> +       u8 r = 128;
> +
> +       /* Avoid division by 0 and count 1 cannot be greater than count 0 */
> +       if (c0 && (c1 <= c0))
> +               r = c1 * 128 / c0;
> +       else
> +               return -1;
> +
> +       /* Calculare LUX */
> +       lux = ((c0 - c1) * ratio_lut[r]) / 256;
> +
> +       /* LUX range check */
> +       return lux > TSL2550_MAX_LUX ? TSL2550_MAX_LUX : lux;
> +}
> +
> +/* --- SysFS support ------------------------------------------------------- */
> +
> +static ssize_t tsl2550_show_power_state(struct device *dev, struct device_attribute *attr, char *buf)
> +{
> +       struct tsl2550_data *data = i2c_get_clientdata(to_i2c_client(dev));
> +
> +       return sprintf(buf, "%u\n", data->power_state);
> +}
> +
> +static ssize_t tsl2550_store_power_state(struct device *dev, struct device_attribute *attr, const char *buf, size_t count)
> +{
> +       struct i2c_client *client = to_i2c_client(dev);
> +       struct tsl2550_data *data = i2c_get_clientdata(client);
> +       unsigned long val = simple_strtoul(buf, NULL, 10);
> +       int ret;
> +
> +       mutex_lock(&data->update_lock);
> +       ret = tsl2550_set_power_state(client, val);
> +       mutex_unlock(&data->update_lock);
> +
> +       if (ret < 0)
> +               return ret;
> +
> +       return count;
> +}
> +
> +static DEVICE_ATTR(power_state, S_IWUSR | S_IRUGO,
> +                  tsl2550_show_power_state, tsl2550_store_power_state);
> +
> +static ssize_t tsl2550_show_operating_mode(struct device *dev, struct device_attribute *attr, char *buf)
> +{
> +       struct tsl2550_data *data = i2c_get_clientdata(to_i2c_client(dev));
> +
> +       return sprintf(buf, "%u\n", data->operating_mode);
> +}
> +
> +static ssize_t tsl2550_store_operating_mode(struct device *dev, struct device_attribute *attr, const char *buf, size_t count)
> +{
> +       struct i2c_client *client = to_i2c_client(dev);
> +       struct tsl2550_data *data = i2c_get_clientdata(client);
> +       unsigned long val = simple_strtoul(buf, NULL, 10);
> +       int ret;
> +
> +       mutex_lock(&data->update_lock);
> +       ret = tsl2550_set_operating_mode(client, val);
> +       mutex_unlock(&data->update_lock);
> +
> +       if (ret < 0)
> +               return ret;
> +
> +       return count;
> +}
> +
> +static DEVICE_ATTR(operating_mode, S_IWUSR | S_IRUGO,
> +                  tsl2550_show_operating_mode, tsl2550_store_operating_mode);
> +
> +static ssize_t __tsl2550_show_lux(struct i2c_client *client, struct device_attribute *attr, char *buf)
> +{
> +       u8 ch0, ch1;
> +       int ret;
> +
> +       ret = tsl2550_get_adc_value(client, 0);
> +       if (ret < 0)
> +               return ret;
> +       ch0 = (u8) ret;
> +
> +       mdelay(1);
> +
> +       ret = tsl2550_get_adc_value(client, 1);
> +       if (ret < 0)
> +               return ret;
> +       ch1 = (u8) ret;
> +
> +       /* Do the job */
> +       ret = tsl2550_calculate_lux(ch0, ch1);
> +       if (ret < 0)
> +               return ret;
> +
> +       return sprintf(buf, "%u\n", ret);
> +}
> +
> +static ssize_t tsl2550_show_lux(struct device *dev, struct device_attribute *attr, char *buf)
> +{
> +       struct i2c_client *client = to_i2c_client(dev);
> +       struct tsl2550_data *data = i2c_get_clientdata(client);
> +       int ret;
> +
> +       /* No LUX data if not operational */
> +       if (!data->power_state)
> +               return -EBUSY;
> +
> +       mutex_lock(&data->update_lock);
> +       ret = __tsl2550_show_lux(client, attr, buf);
> +       mutex_unlock(&data->update_lock);
> +
> +       return ret;
> +}
> +
> +static DEVICE_ATTR(lux, S_IRUGO,
> +                  tsl2550_show_lux, NULL);
> +
> +static struct attribute *tsl2550_attributes[] = {
> +       &dev_attr_power_state.attr,
> +       &dev_attr_operating_mode.attr,
> +       &dev_attr_lux.attr,
> +       NULL
> +};
> +
> +static const struct attribute_group tsl2550_attr_group = {
> +       .attrs = tsl2550_attributes,
> +};
> +
> +/* --- Initialization function --------------------------------------------- */
> +
> +static void tsl2550_init_client(struct i2c_client *client)
> +{
> +       struct tsl2550_data *data = i2c_get_clientdata(client);
> +
> +       /* Power up the device and set the default operating mode */
> +       tsl2550_set_power_state(client, 1);
> +       tsl2550_set_operating_mode(client, data->operating_mode);
> +}
> +
> +/* --- I2C init/probing/exit functions ------------------------------------- */
> +
> +static struct i2c_driver tsl2550_driver;
> +static int __devinit tsl2550_probe(struct i2c_client *client)
> +{
> +       struct i2c_adapter *adapter = to_i2c_adapter(client->dev.parent);
> +       struct tsl2550_data *data;
> +       int *opmode, err = 0;
> +
> +       if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE
> +                                    | I2C_FUNC_SMBUS_WRITE_BYTE_DATA))
> +               goto exit;

On "exit" you are returning value of "err" which is zero as per first
exit above. You should
first set "err" to relevant error flag and then exit.

> +
> +       data = kzalloc(sizeof(struct tsl2550_data), GFP_KERNEL);
> +       if (!data) {
> +               err = -ENOMEM;
> +               goto exit;
> +       }
> +       data->client = client;
> +       strncpy(client->name, TSL2550_DRV_NAME, I2C_NAME_SIZE);

You can use "type" field in i2c_board_info structure to pass the
client's name. As this name is being copied to client->name by
i2c_new_device, and it could be useful in future to different next
version of the very much similar chips using this field.

> +       i2c_set_clientdata(client, data);
> +
> +       /* Check platform data */
> +       opmode = client->dev.platform_data;
> +       if (opmode) {
> +               if (*opmode < 0 || *opmode > 1) {
> +                       dev_err(&client->dev, "invalid operating_mode (%d)\n",
> +                                       *opmode);
> +                       err = -EINVAL;
> +                       goto exit_kfree;
> +               }
> +               data->operating_mode = *opmode;
> +       }
> +       else

"else" should be with closing "}" bracket not after that.

> +               data->operating_mode = 0;       /* default mode is standard */
> +       dev_info(&client->dev, "%s operating mode\n",
> +                       data->operating_mode ? "extended" : "standard");
> +
> +       /* Probe the chip. To do so we try to power up the device and then to
> +        * read back the 0x03 code */
> +       err = i2c_smbus_write_byte(client, TSL2550_POWER_UP);
> +       if (err < 0)
> +               goto exit_kfree;
> +       mdelay(1);
> +       err = i2c_smbus_read_byte(client);
> +       if (err != TSL2550_POWER_UP) {
> +               err = -ENODEV;
> +               goto exit_kfree;
> +       }
> +
> +       mutex_init(&data->update_lock);
> +
> +       /* Initialize the TSL2550 chip */
> +       tsl2550_init_client(client);
> +
> +       /* Register sysfs hooks */
> +       err = sysfs_create_group(&client->dev.kobj, &tsl2550_attr_group);
> +       if (err)
> +               goto exit_kfree;
> +
> +       dev_info(&client->dev,
> +               "TSL2550 I2C support enabled - ver. %s\n", DRIVER_VERSION);
> +       dev_info(&client->dev,
> +               "Copyright (C) 2007 Rodolfo Giometti <giometti@...ux.it>\n");
> +
> +       return 0;
> +
> +exit_kfree:
> +       kfree(data);
> +exit:
> +       return err;
> +}
> +
> +static int __devexit tsl2550_remove(struct i2c_client *client)
> +{
> +       sysfs_remove_group(&client->dev.kobj, &tsl2550_attr_group);
> +
> +       /* Power doen the device */
> +       tsl2550_set_power_state(client, 0);
> +
> +       kfree(i2c_get_clientdata(client));
> +
> +       return 0;
> +}
> +
> +static struct i2c_driver tsl2550_driver = {
> +       .driver = {
> +               .name   = TSL2550_DRV_NAME,
> +               .owner  = THIS_MODULE,
> +       },
> +       .probe  = tsl2550_probe,
> +       .remove = __devexit_p(tsl2550_remove),
> +};
> +
> +static int __init tsl2550_init(void)
> +{
> +       return i2c_add_driver(&tsl2550_driver);
> +}
> +
> +static void __exit tsl2550_exit(void)
> +{
> +       i2c_del_driver(&tsl2550_driver);
> +}
> +
> +MODULE_AUTHOR("Rodolfo Giometti <giometti@...ux.it>");
> +MODULE_DESCRIPTION("TSL2550 ambient light sensor driver");
> +MODULE_LICENSE("GPL");
> +
> +module_init(tsl2550_init);
> +module_exit(tsl2550_exit);


-- 
--Trilok Soni
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