Date:	Sun, 16 Sep 2012 17:41:18 +0200
From:	Lars-Peter Clausen <lars@...afoo.de>
To:	anish kumar <anish198519851985@...il.com>
CC:	jic23@....ac.uk, cbou@...l.ru, linux-kernel@...r.kernel.org,
	linux-iio@...r.kernel.org
Subject: Re: [PATCH] [V1]power: battery: Generic battery driver using IIO

On 09/16/2012 09:14 AM, anish kumar wrote:
> From: anish kumar <anish198519851985@...il.com>
> 
> In last version:
> Addressed concerns raised by lars:
> a. made the adc_bat per device.
> b. get the IIO channel using hardcoded channel names.
> c. Minor issues related to gpio_is_valid and some code
>    refactoring.
> 
> In this version:
> Addressed concerns raised by Anton:
> a. changed the struct name to gab(generic adc battery).
> b. Added some functions to neaten the code.
> c. Some minor coding guidelines changes.
> d. Used the latest function introduce by lars:
>    iio_read_channel_processed to streamline the code.
> 
> Signed-off-by: anish kumar <anish198519851985@...il.com>
> ---
>  drivers/power/generic-adc-battery.c       |  442 +++++++++++++++++++++++++++++
>  include/linux/power/generic-adc-battery.h |   19 ++
>  2 files changed, 461 insertions(+), 0 deletions(-)
>  create mode 100644 drivers/power/generic-adc-battery.c
>  create mode 100644 include/linux/power/generic-adc-battery.h
> 
> diff --git a/drivers/power/generic-adc-battery.c b/drivers/power/generic-adc-battery.c
> new file mode 100644
> index 0000000..fd62916
> --- /dev/null
> +++ b/drivers/power/generic-adc-battery.c
> @@ -0,0 +1,442 @@
> +/*
> + * Generic battery driver code using IIO
> + * Copyright (C) 2012, Anish Kumar <anish198519851985@...il.com>
> + * based on jz4740-battery.c
> + * based on s3c_adc_battery.c
> + *
> + * This file is subject to the terms and conditions of the GNU General Public
> + * License.  See the file COPYING in the main directory of this archive for
> + * more details.
> + *
> + */
> +#include <linux/interrupt.h>
> +#include <linux/platform_device.h>
> +#include <linux/power_supply.h>
> +#include <linux/gpio.h>
> +#include <linux/err.h>
> +#include <linux/timer.h>
> +#include <linux/jiffies.h>
> +#include <linux/errno.h>
> +#include <linux/init.h>
> +#include <linux/module.h>
> +#include <linux/slab.h>
> +#include <linux/iio/consumer.h>
> +#include <linux/iio/types.h>
> +#include <linux/power/generic-adc-battery.h>
> +
> +enum gab_chan_type {
> +	VOLTAGE = 0,
> +	CURRENT,
> +	POWER,
> +	MAX_CHAN_TYPE
> +};
> +
> +/*
> + * gab_chan_name suggests the standard channel names for commonly used
> + * channel types.
> + */
> +static char *gab_chan_name[] = {

const char *const

> +	[VOLTAGE]	= "voltage",
> +	[CURRENT]	= "current",
> +	[POWER]		= "power",
> +};
> +
> +struct gab {
> +	struct power_supply	psy;
> +	struct iio_channel	**channel;
> +	struct gab_platform_data	*pdata;
> +	struct delayed_work bat_work;
> +	int		was_plugged;
> +	int		volt_value;
> +	int		cur_value;

The two above are never really used.

> +	int		level;
> +	int		status;
> +	int		cable_plugged:1;
> +};
[...]
> +static enum power_supply_property gab_props[] = {
const
> +	POWER_SUPPLY_PROP_STATUS,
> +	POWER_SUPPLY_PROP_CHARGE_FULL_DESIGN,
> +	POWER_SUPPLY_PROP_CHARGE_EMPTY_DESIGN,
> +	POWER_SUPPLY_PROP_CHARGE_NOW,
> +	POWER_SUPPLY_PROP_VOLTAGE_NOW,
> +	POWER_SUPPLY_PROP_CURRENT_NOW,
> +	POWER_SUPPLY_PROP_TECHNOLOGY,
> +	POWER_SUPPLY_PROP_VOLTAGE_MIN_DESIGN,
> +	POWER_SUPPLY_PROP_VOLTAGE_MAX_DESIGN,
> +	POWER_SUPPLY_PROP_MODEL_NAME,
> +};
> +
> +/*
> + * This properties are set based on the received platform data and this
> + * should correspond one-to-one with enum chan_type.
> + */
> +static enum power_supply_property gab_dyn_props[] = {
const
> +	POWER_SUPPLY_PROP_VOLTAGE_NOW,
> +	POWER_SUPPLY_PROP_CURRENT_NOW,
> +	POWER_SUPPLY_PROP_POWER_NOW,
> +};
> +
> +static bool charge_finished(struct gab *adc_bat)

missing prefix

> +{
> +	bool ret = gpio_get_value(adc_bat->pdata->gpio_charge_finished);
> +	bool inv = adc_bat->pdata->gpio_inverted;
> +
> +	return ret ^ inv;
> +}
> +
> +int gab_get_status(struct gab *adc_bat)
static
> +{
> +	struct gab_platform_data *pdata = adc_bat->pdata;
> +	int chg_gpio = pdata->gpio_charge_finished;
> +
> +	if (!gpio_is_valid(chg_gpio) || adc_bat->level < 100000)

level is never really set, is it? Also the 100000 seems to come directly from
the s3c_adc_battery driver, while this value may be different for every
battery. I'd use the bat_info->charge_full_design here. Also I'd remove the
!gpio_is_valid(chg_gpio)  I don't see a reason why the battery could not be
fully charged even though no charger gpio is given.

> +		return adc_bat->status;
> +
> +	return POWER_SUPPLY_STATUS_FULL;
> +}
> +
> +enum gab_chan_type gab_prop_to_chan(enum power_supply_property psp)
static
> +{
> +	switch (psp) {
> +	case POWER_SUPPLY_PROP_POWER_NOW:
> +		return POWER;
> +	case POWER_SUPPLY_PROP_VOLTAGE_NOW:
> +		return VOLTAGE;
> +	case POWER_SUPPLY_PROP_CURRENT_NOW:
> +		return CURRENT;
> +	default:
> +		WARN_ON(1);

This WARN_ON will be hit quite often.

> +	}
> +	return POWER;
> +}
> +
> +int read_channel(struct gab *adc_bat, enum power_supply_property psp,
> +		int *result)
static
> +{
> +	int ret = 0;
> +	int chan_index;
> +
> +	chan_index = gab_prop_to_chan(psp);
> +	ret = iio_read_channel_processed(adc_bat->channel[chan_index],
> +			result);
> +	if (ret < 0)
> +		pr_err("read channel error\n");
> +	return ret;
> +}
> +
> +static int gab_get_property(struct power_supply *psy,
> +		enum power_supply_property psp, union power_supply_propval *val)
> +{
> +	struct gab *adc_bat;
> +	struct gab_platform_data *pdata;
> +	struct power_supply_info *bat_info;
> +	int result;
> +	int ret = 0;
> +
> +	adc_bat = to_generic_bat(psy);
> +	if (!adc_bat) {
> +		dev_err(psy->dev, "no battery infos ?!\n");
> +		return -EINVAL;
> +	}
> +	pdata = adc_bat->pdata;
> +	bat_info = &pdata->battery_info;
> +
> +	ret = read_channel(adc_bat, psp, &result);
> +	if (ret < 0)
> +		goto err;
> +
> +	switch (psp) {
> +	case POWER_SUPPLY_PROP_STATUS:
> +		gab_get_status(adc_bat);
> +		break;
> +	case POWER_SUPPLY_PROP_CHARGE_EMPTY_DESIGN:
> +		val->intval = 0;
> +		break;
> +	case POWER_SUPPLY_PROP_CHARGE_NOW:
> +		val->intval = pdata->cal_charge(result);
> +		break;
> +	case POWER_SUPPLY_PROP_VOLTAGE_NOW:
> +		val->intval = result;
> +		break;
> +	case POWER_SUPPLY_PROP_CURRENT_NOW:
> +		val->intval = result;
> +		break;
> +	case POWER_SUPPLY_PROP_POWER_NOW:
> +		val->intval = result;

I'd do it this way, that also avoids all the WARN_ONs earlier

	case POWER_SUPPLY_PROP_VOLTAGE_NOW
	case POWER_SUPPLY_PROP_CURRENT_NOW:
	case POWER_SUPPLY_PROP_POWER_NOW:
		ret = read_channel(adc_bat, psp, &result);
		if (ret < 0)		
			return ret
		val->intval = result;


> +		break;
> +	case POWER_SUPPLY_PROP_TECHNOLOGY:
> +		val->intval = bat_info->technology;
> +		break;
> +	case POWER_SUPPLY_PROP_VOLTAGE_MIN_DESIGN:
> +		val->intval = bat_info->voltage_min_design;
> +		break;
> +	case POWER_SUPPLY_PROP_VOLTAGE_MAX_DESIGN:
> +		val->intval = bat_info->voltage_max_design;
> +		break;
> +	case POWER_SUPPLY_PROP_CHARGE_FULL_DESIGN:
> +		val->intval = bat_info->charge_full_design;
> +		break;
> +	case POWER_SUPPLY_PROP_MODEL_NAME:
> +		val->strval = bat_info->name;
> +		break;
> +	default:
> +		return -EINVAL;
> +	}
> +err:
> +	return ret;
> +}
> +
> +static void gab_work(struct work_struct *work)
> +{
> +	struct gab *adc_bat;
> +	struct gab_platform_data *pdata;
> +	struct delayed_work *delayed_work;
> +	int is_charged;
> +	int is_plugged;
> +
> +	delayed_work = container_of(work, struct delayed_work, work);
> +	adc_bat = container_of(delayed_work, struct gab, bat_work);
> +	pdata = adc_bat->pdata;
> +
> +	is_plugged = power_supply_am_i_supplied(&adc_bat->psy);
> +	adc_bat->cable_plugged = is_plugged;
> +	if (is_plugged != adc_bat->was_plugged) {
> +		adc_bat->was_plugged = is_plugged;

I don't thin was_plugged is necessary. If is unplugged it is discharging, if it
is plugged it is either charging or full. And I think that's the logic that
should be used to set status. Something like.

if (!is_plugged)
	adc_bat->status =  POWER_SUPPLY_STATUS_DISCHARGING;
else if (charge_finished(adc_bat))
	adc_bat->status = POWER_SUPPLY_STATUS_FULL;

Maybe POWER_SUPPLY_STATUS_NOT_CHARGING is the better status here since we do
not necessarily know that it is full.

else
	adc_bat->status = POWER_SUPPLY_STATUS_CHARGING;

This assumes that the gpio_is_valid checking is done in charge_finished and if
it returns false charge_finished just returns false.

> +		if (is_plugged)
> +			adc_bat->status = POWER_SUPPLY_STATUS_CHARGING;
> +		else
> +			adc_bat->status = POWER_SUPPLY_STATUS_DISCHARGING;
> +	} else {
> +		if (gpio_is_valid(pdata->gpio_charge_finished)) {
> +			if (is_plugged) {
> +				is_charged = charge_finished(adc_bat);
> +				if (is_charged)
> +					adc_bat->status =
> +						POWER_SUPPLY_STATUS_FULL;
> +				else
> +					adc_bat->status =
> +						POWER_SUPPLY_STATUS_CHARGING;
> +			}
> +		}
> +	}
> +
> +	power_supply_changed(&adc_bat->psy);

It makes probably sense to make a copy of adc_bat->status and if it did not
change don't generate an event.

> +}
> +
> +static irqreturn_t gab_charged(int irq, void *dev_id)
> +{
> +	struct gab *adc_bat = dev_id;
> +
> +	schedule_delayed_work(&adc_bat->bat_work,
> +			msecs_to_jiffies(adc_bat->pdata->jitter_delay));

I would use a default jitter delay if it is 0. Does this make sense?

> +	return IRQ_HANDLED;
> +}
> +
> +static int __devinit gab_probe(struct platform_device *pdev)
> +{
> +	struct gab *adc_bat;
> +	struct power_supply	*psy;
> +	struct gab_platform_data *pdata = pdev->dev.platform_data;
> +	int ret;
> +	int num_chans;
> +	int fail = 0;
> +
> +	adc_bat = devm_kzalloc(&pdev->dev, sizeof(*adc_bat), GFP_KERNEL);
> +	if (!adc_bat) {
> +		dev_err(&pdev->dev, "failed to allocate memory\n");
> +		return -ENOMEM;
> +	}
> +
> +	psy = &adc_bat->psy;
> +
> +	/* copying the battery name from platform data */
> +	psy->name = pdata->battery_name;
> +
> +	/* bootup default values for the battery */
> +	adc_bat->volt_value = -1;
> +	adc_bat->cur_value = -1;
> +	adc_bat->cable_plugged = 0;
> +	adc_bat->status = POWER_SUPPLY_STATUS_DISCHARGING;
> +	psy->type = POWER_SUPPLY_TYPE_BATTERY;
> +	psy->get_property = gab_get_property;
> +	psy->external_power_changed = gab_ext_power_changed;
> +	adc_bat->pdata = pdata;
> +
> +	/* calculate the total number of channels */
> +	num_chans = ARRAY_SIZE(gab_chan_name);
> +
> +	/*
> +	 * copying the static properties and allocating extra memory for holding
> +	 * the extra configurable properties received from platform data.
> +	 */
> +	psy->properties = devm_kzalloc(&pdev->dev, sizeof(gab_props) +
> +			sizeof(*(psy->properties)) * num_chans,	GFP_KERNEL);

Maybe use kcalloc here with ARRAY_SIZE(gab_props) + ARRAY_SIZE(gab_chan_name)
as first parameter and sizeof(*psy->properties) as second.

> +	if (!psy->properties) {
> +		ret = -ENOMEM;
> +		goto first_mem_fail;
> +	}
> +
> +	memcpy(psy->properties, gab_props, sizeof(gab_props));
> +
> +	/* allocating memory for iio channels */
> +	adc_bat->channel = devm_kzalloc(&pdev->dev,
> +				num_chans * sizeof(struct iio_channel),
> +					GFP_KERNEL);

Since the size is const you could just make channel an aray in the gab struct
and this allocation would not be needed.

> +	if (!adc_bat->channel) {
> +		ret = -ENOMEM;
> +		goto first_mem_fail;
> +	}
> +
> +	/*
> +	 * getting channel from iio and copying the battery properties
> +	 * based on the channel supported by consumer device.
> +	 */
> +	for (num_chans = 0; gab_chan_name[num_chans]; num_chans++) {

This won't work since gab_chan_name is not NULL terminated. Just make it
num_chans < ARRAY_SIZE(gab_chan_name). Btw. num_chans is really a bad name in
this case since it is an iterator variable. Just call it chan or something like
that.

> +		adc_bat->channel[num_chans] =
> +			iio_channel_get(dev_name(&pdev->dev),
> +					gab_chan_name[num_chans]);
> +		/* we skip for channels which fail */
> +		if (IS_ERR(adc_bat->channel[num_chans])) {
> +			pr_err("%s failed\n", gab_chan_name[num_chans]);

No error message here it will be quite likely that a battery does not provide
all three types of channels.

> +			fail++;
> +		} else {
> +			static int index;

static?! Move it outsize of the loop an initialize it to ARRAY_SIZE(gab_props)
then you can skip the "extra + sizeof(gab_props)" here.

> +			memcpy(psy->properties + sizeof(gab_props) +
> +					sizeof(*(psy->properties))*index,
> +					&gab_dyn_props[num_chans],
> +					sizeof(gab_dyn_props[num_chans]));
> +			index++;
> +		}
> +	}
> +
> +	/* none of the channels are supported so let's bail out */
> +	if (fail == num_chans) {

Just check whether index is != 0, you don't need to count the failed requests then.

> +		ret = PTR_ERR(adc_bat->channel[num_chans]);

num_chans will be outside of bounds of channel at this point.

> +		goto first_mem_fail;
> +	}
> +
> +	/*
> +	 * Total number of properties is equal to static properties
> +	 * plus the dynamic properties.Some properties may not be set
> +	 * as come channels may be not be supported by the device.So
> +	 * we need to take care of that.
> +	 */
> +	psy->num_properties = ARRAY_SIZE(gab_props) +
> +		ARRAY_SIZE(gab_dyn_props) - fail;
> +
> +	ret = power_supply_register(&pdev->dev, psy);
> +	if (ret)
> +		goto err_reg_fail;
> +
> +	INIT_DELAYED_WORK(&adc_bat->bat_work, gab_work);
> +
> +	if (gpio_is_valid(pdata->gpio_charge_finished)) {
> +		int irq;
> +		ret = gpio_request(pdata->gpio_charge_finished, "charged");
> +		if (ret)
> +			goto err_gpio;
> +
> +		irq = gpio_to_irq(pdata->gpio_charge_finished);
> +		ret = request_any_context_irq(irq, gab_charged,
> +				IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING,
> +				"battery charged", &adc_bat);

Just "adc_bat", not "&adc_bat"

> +		if (ret)
> +			goto err_gpio;

			You also need to free the if requesting the gpio fails.

> +	} else
> +		goto err_gpio; /* let's bail out */
> +
> +	platform_set_drvdata(pdev, &adc_bat);

Same here

> +
> +	/* Schedule timer to check current status */
> +	schedule_delayed_work(&adc_bat->bat_work,
> +			msecs_to_jiffies(0));
> +	return 0;
> +
> +err_gpio:
> +	power_supply_unregister(psy);
> +err_reg_fail:
> +	for (num_chans = 0; gab_chan_name[num_chans]; num_chans++)

Here again, it's not NULL terminated

> +		iio_channel_release(adc_bat->channel[num_chans]);
> +first_mem_fail:
> +	return ret;
> +}
> +
> +static int gab_remove(struct platform_device *pdev)
__devexit
> +{
> +	int num_chans;
> +	struct gab_platform_data	*pdata;
> +	struct gab *adc_bat = platform_get_drvdata(pdev);
> +
> +	pdata = adc_bat->pdata;
> +	power_supply_unregister(&adc_bat->psy);
> +
> +	if (gpio_is_valid(pdata->gpio_charge_finished)) {
> +		free_irq(gpio_to_irq(pdata->gpio_charge_finished), NULL);

Needs adc_bat as the second agument

> +		gpio_free(pdata->gpio_charge_finished);
> +	}
> +
> +	for (num_chans = 0; gab_chan_name[num_chans]; num_chans++)

And also here, it's not NULL terminated

> +		iio_channel_release(adc_bat->channel[num_chans]);
> +	cancel_delayed_work(&adc_bat->bat_work);
> +	return 0;
> +}
> +
[...]
> +
> +static struct platform_driver gab_driver = {
> +	.driver		= {
> +		.name	= "generic-adc-battery",
> +		.owner	= THIS_MODULE,
> +		.pm	= GAB_PM_OPS
> +	},
> +	.probe		= gab_probe,
> +	.remove		= gab_remove,

__devexit_p

> +};
> +module_platform_driver(gab_driver);
> +
> +MODULE_AUTHOR("anish kumar <anish198519851985@...il.com>");
> +MODULE_DESCRIPTION("generic battery driver using IIO");
> +MODULE_LICENSE("GPL");
> diff --git a/include/linux/power/generic-adc-battery.h b/include/linux/power/generic-adc-battery.h
> new file mode 100644
> index 0000000..8f02e9e
> --- /dev/null
> +++ b/include/linux/power/generic-adc-battery.h
> @@ -0,0 +1,19 @@
> +/*
> + * 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.
> + */
> +
> +#ifndef GENERIC_ADC_BATTERY_H
> +#define GENERIC_ADC_BATTERY_H
> +

Kernel doc for the struct would be nice.

> +struct gab_platform_data {
> +	struct power_supply_info battery_info;
> +	char	*battery_name;

The power_supply_info struct also has a name field, it would make sense to use it.

> +	int	(*cal_charge)(long value);
> +	int	gpio_charge_finished;
> +	bool	gpio_inverted;
> +	int	jitter_delay;
> +};
> +
> +#endif /* GENERIC_ADC_BATTERY_H */

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