Date:	Fri, 21 May 2010 18:10:00 +0530
From:	"Hemanth V" <hemanthv@...com>
To:	"Daniel Mack" <daniel@...aq.de>
Cc:	<linux-kernel@...r.kernel.org>, <linux-omap@...r.kernel.org>,
	<linux-input@...r.kernel.org>
Subject: Re: [RFC] [PATCH] misc : ROHM BH1780GLI Ambient light sensor Driver

----- Original Message ----- 
From: "Daniel Mack" <daniel@...aq.de>
To: "Hemanth V" <hemanthv@...com>
Cc: <linux-kernel@...r.kernel.org>; <linux-omap@...r.kernel.org>; 
<linux-input@...r.kernel.org>
Sent: Friday, May 21, 2010 5:33 PM
Subject: Re: [RFC] [PATCH] misc : ROHM BH1780GLI Ambient light sensor Driver


> Hi,
>
> On Fri, May 21, 2010 at 05:05:50PM +0530, Hemanth V wrote:
>> Corrected the mailing list, should be linux-kernel
>>
>> This patch adds support for ROHM BH1780GLI Ambient light sensor.
>>
>> BH1780 supports I2C interface. Driver supports read/update of power state 
>> and
>> read of lux value (through SYSFS). Writing value 3 to power_state enables 
>> the
>> sensor and current lux value could be read.
>
> FWIW, this looks pretty good to me, just some minor things below.

Thanks for the review comment, responses inline

>
> Daniel
>
>> Signed-off-by: Hemanth V <hemanthv@...com>
>> ---
>>  drivers/misc/Kconfig     |   11 ++
>>  drivers/misc/Makefile    |    1 +
>>  drivers/misc/bh1780gli.c |  278 
>> ++++++++++++++++++++++++++++++++++++++++++++++
>>  3 files changed, 290 insertions(+), 0 deletions(-)
>>  create mode 100644 drivers/misc/bh1780gli.c
>>
>> diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
>> index 0d0d625..0687a0c 100644
>> --- a/drivers/misc/Kconfig
>> +++ b/drivers/misc/Kconfig
>> @@ -278,6 +278,17 @@ config SENSORS_TSL2550
>>    This driver can also be built as a module.  If so, the module
>>    will be called tsl2550.
>>
>> +config SENSORS_BH1780
>> + tristate "ROHM BH1780GLI ambient light sensor"
>> + depends on I2C && SYSFS
>> + help
>> +   If you say yes here you get support for the ROHM BH1780GLI
>> +   ambient light sensor.
>> +
>> +   This driver can also be built as a module.  If so, the module
>> +   will be called bh1780gli.
>> +
>> +
>>  config EP93XX_PWM
>>  tristate "EP93xx PWM support"
>>  depends on ARCH_EP93XX
>> diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile
>> index 7b6f7ee..c479d91 100644
>> --- a/drivers/misc/Makefile
>> +++ b/drivers/misc/Makefile
>> @@ -30,3 +30,4 @@ obj-$(CONFIG_IWMC3200TOP)      += iwmc3200top/
>>  obj-y += eeprom/
>>  obj-y += cb710/
>>  obj-$(CONFIG_VMWARE_BALLOON) += vmware_balloon.o
>> +obj-$(CONFIG_SENSORS_BH1780) += bh1780gli.o
>> diff --git a/drivers/misc/bh1780gli.c b/drivers/misc/bh1780gli.c
>> new file mode 100644
>> index 0000000..9b4137d
>> --- /dev/null
>> +++ b/drivers/misc/bh1780gli.c
>> @@ -0,0 +1,278 @@
>> +/*
>> + * bh1780gli.c
>> + * ROHM Ambient Light Sensor Driver
>> + *
>> + * Copyright (C) 2010 Texas Instruments
>> + * Author: Hemanth V <hemanthv@...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.
>> + *
>> + * 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, see <http://www.gnu.org/licenses/>.
>> + */
>> +#include <linux/i2c.h>
>> +#include <linux/slab.h>
>> +#include <linux/mutex.h>
>> +#include <linux/platform_device.h>
>> +#include <linux/delay.h>
>> +
>> +#define BH1780_REG_CONTROL     0x80
>> +#define BH1780_REG_PARTID      0x8A
>> +#define BH1780_REG_MANFID      0x8B
>> +#define BH1780_REG_DLOW        0x8C
>> +#define BH1780_REG_DHIGH       0x8D
>> +
>> +#define BH1780_REVMASK        (0xf)
>> +#define BH1780_POWMASK        (0x3)
>> +#define BH1780_POFF       (0x0)
>> +#define BH1780_PON            (0x3)
>
> Just a nit ... something's wrong with the indentation here.

Will fix

>
>> +/* power on settling time in ms */
>> +#define BH1780_PON_DELAY      2
>> +
>> +struct bh1780_data {
>> + struct i2c_client *client;
>> + int power_state;
>> + /* lock for sysfs operations */
>> + struct mutex lock;
>> +};
>> +
>> +int bh1780_write(struct bh1780_data *ddata, u8 reg, u8 val, char *msg)
>
> Should be static.

Yes, agreed
>
>> +{
>> + int ret = i2c_smbus_write_byte_data(ddata->client, reg, val);
>> + if (ret < 0)
>> + dev_err(&ddata->client->dev,
>> + "i2c_smbus_write_byte_data failed error %d\
>> + Register (%s)\n", ret, msg);
>> + return ret;
>> +}
>> +
>> +int bh1780_read(struct bh1780_data *ddata, u8 reg, char *msg)
>
> Dito.

Yes, agreed
>
>> +{
>> + int ret = i2c_smbus_read_byte_data(ddata->client, reg);
>> + if (ret < 0)
>> + dev_err(&ddata->client->dev,
>> + "i2c_smbus_read_byte_data failed error %d\
>> + Register (%s)\n", ret, msg);
>> + return ret;
>> +}
>> +
>> +static ssize_t bh1780_show_lux(struct device *dev,
>> + struct device_attribute *attr, char *buf)
>> +{
>> +
>> + struct platform_device *pdev = to_platform_device(dev);
>> + struct bh1780_data *ddata = platform_get_drvdata(pdev);
>> + int lsb, msb;
>> +
>> + lsb = bh1780_read(ddata, BH1780_REG_DLOW, "DLOW");
>> + if (lsb < 0)
>> + return lsb;
>> +
>> + msb = bh1780_read(ddata, BH1780_REG_DHIGH, "DHIGH");
>> + if (msb < 0)
>> + return msb;
>> +
>> + return sprintf(buf, "%d\n", (msb << 8) | lsb);
>> +}
>> +
>> +static ssize_t bh1780_show_power_state(struct device *dev,
>> + struct device_attribute *attr,
>> + char *buf)
>> +{
>> + struct platform_device *pdev = to_platform_device(dev);
>> + struct bh1780_data *ddata = platform_get_drvdata(pdev);
>> + int state;
>> +
>> + state = bh1780_read(ddata, BH1780_REG_CONTROL, "CONTROL");
>> + if (state < 0)
>> + return state;
>> +
>> + return sprintf(buf, "%d\n", state & BH1780_POWMASK);
>> +}
>> +
>> +static ssize_t bh1780_store_power_state(struct device *dev,
>> + struct device_attribute *attr,
>> + const char *buf, size_t count)
>> +{
>> + struct platform_device *pdev = to_platform_device(dev);
>> + struct bh1780_data *ddata = platform_get_drvdata(pdev);
>> + unsigned long val;
>> + int error;
>> +
>> + error = strict_strtoul(buf, 0, &val);
>> + if (error)
>> + return error;
>> +
>> + if (val < BH1780_POFF || val > BH1780_PON)
>> + return -EINVAL;
>> +
>> + mutex_lock(&ddata->lock);
>> +
>> + error = bh1780_write(ddata, BH1780_REG_CONTROL, val, "CONTROL");
>> + if (error < 0) {
>> + mutex_unlock(&ddata->lock);
>> + return error;
>> + }
>> +
>> + msleep(BH1780_PON_DELAY);
>
> Hmm, what do you wait for here?

Settling time delay required before lux read out

>
>> + ddata->power_state = val;
>> + mutex_unlock(&ddata->lock);
>
> And I don't get the usage of the mutex here. Can you explain?

Basically prevent two concurrent sysfs calls from interfering
with each other

>
>> + return count;
>> +
>> +}
>
> Remove the empty line. Or move it above the return statement.

Yes, agreed

>
>> +
>> +static DEVICE_ATTR(lux, S_IRUGO, bh1780_show_lux, NULL);
>> +
>> +static DEVICE_ATTR(power_state, S_IWUSR | S_IRUGO,
>> + bh1780_show_power_state, bh1780_store_power_state);
>> +
>> +static struct attribute *bh1780_attributes[] = {
>> + &dev_attr_power_state.attr,
>> + &dev_attr_lux.attr,
>> + NULL
>> +};
>> +
>> +static const struct attribute_group bh1780_attr_group = {
>> + .attrs = bh1780_attributes,
>> +};
>> +
>> +static int __devinit bh1780_probe(struct i2c_client *client,
>> + const struct i2c_device_id *id)
>> +{
>> + int ret;
>> + struct bh1780_data *ddata = NULL;
>
> The initialization isn't needed.

This is basically added for the first goto error, to prevent
any garbage values

>
>> + struct i2c_adapter *adapter = to_i2c_adapter(client->dev.parent);
>> +
>> + if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE)) {
>> + ret = -EIO;
>> + goto err_op_failed;
>> + }
>> +
>> + ddata = kzalloc(sizeof(struct bh1780_data), GFP_KERNEL);
>> + if (ddata == NULL) {
>> + ret = -ENOMEM;
>> + goto err_op_failed;
>> + }
>> +
>> + ddata->client = client;
>> + i2c_set_clientdata(client, ddata);
>> +
>> + ret = bh1780_read(ddata, BH1780_REG_PARTID, "PART ID");
>> + if (ret < 0)
>> + goto err_op_failed;
>> +
>> + dev_info(&client->dev, "Ambient Light Sensor, Rev : %d\n",
>> + (ret & BH1780_REVMASK));
>> +
>> + mutex_init(&ddata->lock);
>> +
>> + ret = sysfs_create_group(&client->dev.kobj, &bh1780_attr_group);
>> + if (ret)
>> + goto err_op_failed;
>> +
>> + return 0;
>> +
>> +err_op_failed:
>> + if (ddata != NULL)
>> + kfree(ddata);
>
> kfree() is resitant against NULL pointers, so you can call it
> unconditionally.

Yes, agreed

>
>> +
>> + return ret;
>> +}
>> +
>> +static int __devexit bh1780_remove(struct i2c_client *client)
>> +{
>> + struct bh1780_data *ddata;
>> +
>> + ddata = i2c_get_clientdata(client);
>> + sysfs_remove_group(&client->dev.kobj, &bh1780_attr_group);
>> +
>> + if (ddata != NULL) {
>> + i2c_set_clientdata(client, NULL);
>> + kfree(ddata);
>> + }
>
> Same here.

Yes, agreed

>
>> +
>> + return 0;
>> +}
>> +
>> +#ifdef CONFIG_PM
>> +static int bh1780_suspend(struct i2c_client *client, pm_message_t mesg)
>> +{
>> + struct bh1780_data *ddata;
>> + int state, ret;
>> +
>> + ddata = i2c_get_clientdata(client);
>> + state = bh1780_read(ddata, BH1780_REG_CONTROL, "CONTROL");
>> + if (state < 0)
>> + return state;
>> +
>> + ddata->power_state = state & BH1780_POWMASK;
>> +
>> + ret = bh1780_write(ddata, BH1780_REG_CONTROL, BH1780_POFF,
>> + "CONTROL");
>> +
>> + if (ret < 0)
>> + return ret;
>> +
>> + return 0;
>> +}
>> +
>> +static int bh1780_resume(struct i2c_client *client)
>> +{
>> + struct bh1780_data *ddata;
>> + int state, ret;
>> +
>> + ddata = i2c_get_clientdata(client);
>> + state = ddata->power_state;
>> +
>> + ret = bh1780_write(ddata, BH1780_REG_CONTROL, state,
>> + "CONTROL");
>> +
>> + if (ret < 0)
>> + return ret;
>> +
>> + return 0;
>> +}
>
> #else
> static inline int bh1780_suspend(struct i2c_client *client, pm_message_t 
> mesg) {}
> static inline int bh1780_resume(struct i2c_client *client) {}
>

Yes, I could add as below which seems to be used in quite a few
misc drivers

#define bh1780_suspend NULL

>
>> +#endif
>> +
>> +static const struct i2c_device_id bh1780_id[] = {
>> + { "bh1780", 0 },
>> + { },
>> +};
>> +
>> +static struct i2c_driver bh1780_driver = {
>> + .probe = bh1780_probe,
>> + .remove = bh1780_remove,
>> + .id_table = bh1780_id,
>> +#ifdef CONFIG_PM
>
> ... then this #ifdef can go away.
>
>> + .suspend = bh1780_suspend,
>> + .resume = bh1780_resume,
>> +#endif
>> + .driver = {
>> + .name = "bh1780"
>> + },
>> +};
>> +
>> +static int __init bh1780_init(void)
>> +{
>> + return i2c_add_driver(&bh1780_driver);
>> +}
>> +
>> +static void __exit bh1780_exit(void)
>> +{
>> + i2c_del_driver(&bh1780_driver);
>> +}
>> +
>> +module_init(bh1780_init)
>> +module_exit(bh1780_exit)
>> +
>> +MODULE_DESCRIPTION("BH1780GLI Ambient Light Sensor Driver");
>> +MODULE_LICENSE("GPL");
>> +MODULE_AUTHOR("Hemanth V <hemanthv@...com>");
>> -- 
>> 1.5.6.3
>>
>> --
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