[PATCH 6/7] [RFC] ds2760 battery driver

[PATCH 6/7] [RFC] ds2760 battery driver

[Anton Vorontsov]

This is driver for batteries with ds2760 chip inside. Such batteries
used in almost every HP iPaq and HTC PDAs/phones.

---
 drivers/battery/Kconfig          |    7 +
 drivers/battery/Makefile         |    1 +
 drivers/battery/ds2760_battery.c |  466 ++++++++++++++++++++++++++++++++++++++
 include/linux/ds2760_battery.h   |   32 +++
 4 files changed, 506 insertions(+), 0 deletions(-)
 create mode 100644 drivers/battery/ds2760_battery.c
 create mode 100644 include/linux/ds2760_battery.h

diff --git a/drivers/battery/Kconfig b/drivers/battery/Kconfig
index c386593..0c14ae0 100644
--- a/drivers/battery/Kconfig
+++ b/drivers/battery/Kconfig
@@ -8,4 +8,11 @@ config BATTERY
 	  Say Y here to enable generic battery status reporting in
 	  the /sys filesystem.
 
+config BATTERY_DS2760
+	tristate "DS2760 battery driver (HP iPAQ & others)"
+	depends on BATTERY && W1
+	select W1_SLAVE_DS2760
+	help
+	  Say Y here to enable support for batteries with ds2760 chip.
+
 endmenu
diff --git a/drivers/battery/Makefile b/drivers/battery/Makefile
index a2239cb..9902513 100644
--- a/drivers/battery/Makefile
+++ b/drivers/battery/Makefile
@@ -1 +1,2 @@
 obj-$(CONFIG_BATTERY)              += battery.o
+obj-$(CONFIG_BATTERY_DS2760)       += ds2760_battery.o
diff --git a/drivers/battery/ds2760_battery.c b/drivers/battery/ds2760_battery.c
new file mode 100644
index 0000000..a686304
--- /dev/null
+++ b/drivers/battery/ds2760_battery.c
@@ -0,0 +1,466 @@
+/*
+ * Driver for batteries with DS2760 chips inside.
+ *
+ * Copyright (c) 2007 Anton Vorontsov
+ *               2004 Matt Reimer
+ *               2004 Szabolcs Gyurko
+ *
+ * Use consistent with the GNU GPL is permitted,
+ * provided that this copyright notice is
+ * preserved in its entirety in all copies and derived works.
+ *
+ * Author:  Anton Vorontsov <cbou@mail.ru>
+ *          February 2007
+ *
+ *          Matt Reimer <mreimer@vpop.net>
+ *          April 2004, 2005
+ *
+ *          Szabolcs Gyurko <szabolcs.gyurko@tlt.hu>
+ *          September 2004
+ */
+
+#include <linux/module.h>
+#include <linux/param.h>
+#include <linux/jiffies.h>
+#include <linux/workqueue.h>
+#include <linux/pm.h>
+#include <linux/platform_device.h>
+#include <linux/ds2760_battery.h>
+
+#include "../w1/w1.h"
+#include "../w1/slaves/w1_ds2760.h"
+
+struct ds2760_device_info {
+	struct battery_info *bi;
+
+	/* DS2760 data, valid after calling ds2760_battery_read_status() */
+	unsigned long update_time;      /* jiffies when data read */
+	char raw[DS2760_DATA_SIZE];     /* raw DS2760 data */
+	int voltage_raw;                /* units of 4.88 mV */
+	int voltage_mV;                 /* units of mV */
+	int current_raw;                /* units of 0.625 mA */
+	int current_mA;                 /* units of mA */
+	int accum_current_raw;          /* units of 0.25 mAh */
+	int accum_current_mAh;          /* units of mAh */
+	int temp_raw;                   /* units of 0.125 C */
+	int temp_C;                     /* units of 0.1 C */
+	int rated_capacity;             /* units of mAh */
+	int rem_capacity;               /* percentage */
+	int full_active_mAh;            /* units of mAh */
+	int empty_mAh;                  /* units of mAh */
+	int life_min;                   /* units of minutes */
+	int charge_status;              /* BATTERY_STATUS_* */
+
+	int full_counter;
+	struct battery batt_cdev;
+	struct device *w1_dev;
+	struct workqueue_struct *monitor_wqueue;
+	struct delayed_work monitor_work;
+};
+
+static unsigned int cache_time = 1000;
+module_param(cache_time, uint, 0644);
+MODULE_PARM_DESC(cache_time, "cache time in milliseconds");
+
+/* Some batteries have their rated capacity stored a N * 10 mAh, while
+ * others use an index into this table. */
+static int rated_capacities[] = {
+	0,
+	920,        /* Samsung */
+	920,        /* BYD */
+	920,        /* Lishen */
+	920,        /* NEC */
+	1440,       /* Samsung */
+	1440,       /* BYD */
+	1440,       /* Lishen */
+	1440,       /* NEC */
+	2880,       /* Samsung */
+	2880,       /* BYD */
+	2880,       /* Lishen */
+	2880        /* NEC */
+};
+
+/* array is level at temps 0C, 10C, 20C, 30C, 40C
+ * temp is in Celsius */
+static int battery_interpolate(int array[], int temp)
+{
+	int index, dt;
+
+	if (temp <= 0)
+		return array[0];
+	if (temp >= 40)
+		return array[4];
+
+	index = temp / 10;
+	dt    = temp % 10;
+
+	return array[index] + (((array[index + 1] - array[index]) * dt) / 10);
+}
+
+static int ds2760_battery_read_status(struct ds2760_device_info *di)
+{
+	int ret, i, start, count, scale[5];
+
+	if (di->update_time && time_before(jiffies, di->update_time +
+	                                   msecs_to_jiffies(cache_time)))
+		return 0;
+
+	if (!di->w1_dev)
+		return 0;
+
+	/* The first time we read the entire contents of SRAM/EEPROM,
+	 * but after that we just read the interesting bits that change. */
+	if (di->update_time == 0) {
+		start = 0;
+		count = DS2760_DATA_SIZE;
+	}
+	else {
+		start = DS2760_VOLTAGE_MSB;
+		count = DS2760_TEMP_LSB - start + 1;
+	}
+
+	ret = w1_ds2760_read(di->w1_dev, di->raw + start, start, count);
+	if (ret != count) {
+		printk("call to w1_ds2760_read failed (0x%08x)\n",
+		       (unsigned int)di->w1_dev);
+		return 1;
+	}
+
+	di->update_time = jiffies;
+
+	/* DS2760 reports voltage in units of 4.88mV, but the battery class
+	 * reports in units of mV, so convert by multiplying by 4.875.
+	 * We approximate because integer math is cheap, and close enough. */
+	di->voltage_raw = (di->raw[DS2760_VOLTAGE_MSB] << 3) |
+	                  (di->raw[DS2760_VOLTAGE_LSB] >> 5);
+	di->voltage_mV = (di->voltage_raw * 5) - (di->voltage_raw / 8);
+
+	/* DS2760 reports current in signed units of 0.625mA, but the battery
+	 * class reports in units of mA, so convert by multiplying by 0.625. */
+	di->current_raw =
+	    (((signed char)di->raw[DS2760_CURRENT_MSB]) << 5) |
+	                  (di->raw[DS2760_CURRENT_LSB] >> 3);
+	di->current_mA = (di->current_raw / 2) + (di->current_raw / 8);
+
+	/* DS2760 reports accumulated current in signed units of 0.25mAh. */
+	di->accum_current_raw =
+	    (((signed char)di->raw[DS2760_CURRENT_ACCUM_MSB]) << 8) |
+	                   di->raw[DS2760_CURRENT_ACCUM_LSB];
+	di->accum_current_mAh = di->accum_current_raw / 4;
+
+	/* DS2760 reports temperature in signed units of 0.125C, but the
+	 * battery class reports in units of 1/10 C, so we convert by
+	 * multiplying by .125 * 10 = 1.25. */
+	di->temp_raw = (((signed char)di->raw[DS2760_TEMP_MSB]) << 3) |
+	                             (di->raw[DS2760_TEMP_LSB] >> 5);
+	di->temp_C = di->temp_raw + (di->temp_raw / 4);
+
+	/* At least some battery monitors (e.g. HP iPAQ) store the battery's
+	 * maximum rated capacity. */
+	if (di->raw[DS2760_RATED_CAPACITY] < ARRAY_SIZE(rated_capacities))
+		di->rated_capacity = rated_capacities[
+		        (unsigned int)di->raw[DS2760_RATED_CAPACITY]];
+	else
+		di->rated_capacity = di->raw[DS2760_RATED_CAPACITY] * 10;
+
+	/* Calculate the full level at the present temperature. */
+	di->full_active_mAh = di->raw[DS2760_ACTIVE_FULL] << 8 |
+	                      di->raw[DS2760_ACTIVE_FULL + 1];
+
+	scale[0] = di->raw[DS2760_ACTIVE_FULL] << 8 |
+	           di->raw[DS2760_ACTIVE_FULL + 1];
+	for (i = 1; i < 5; i++)
+		scale[i] = scale[i - 1] + di->raw[DS2760_ACTIVE_FULL + 2 + i];
+
+	di->full_active_mAh = battery_interpolate(scale, di->temp_C / 10);
+
+	/* Calculate the empty level at the present temperature. */
+	scale[4] = di->raw[DS2760_ACTIVE_EMPTY + 4];
+	for (i = 3; i >= 0; i--)
+		scale[i] = scale[i + 1] + di->raw[DS2760_ACTIVE_EMPTY + i];
+
+	di->empty_mAh = battery_interpolate(scale, di->temp_C / 10);
+
+	/* From Maxim Application Note 131: remaining capacity =
+	 * ((ICA - Empty Value) / (Full Value - Empty Value)) x 100% */
+	di->rem_capacity = ((di->accum_current_mAh - di->empty_mAh) * 100) /
+	                    (di->full_active_mAh - di->empty_mAh);
+
+	if (di->rem_capacity < 0)
+		di->rem_capacity = 0;
+	if (di->rem_capacity > 100)
+		di->rem_capacity = 100;
+
+	if (di->current_mA)
+		di->life_min = -((di->accum_current_mAh - di->empty_mAh) *
+		                 60) / di->current_mA;
+	else
+		di->life_min = 0;
+
+	return 0;
+}
+
+static void ds2760_battery_update_status(struct ds2760_device_info *di)
+{
+	int old_charge_status = di->charge_status;
+
+	ds2760_battery_read_status(di);
+
+	if (di->charge_status == BATTERY_STATUS_UNKNOWN)
+		di->full_counter = 0;
+
+	if (battery_is_external_power_supplied(&di->batt_cdev)) {
+		if (di->current_mA > 10) {
+			di->charge_status = BATTERY_STATUS_CHARGING;
+			di->full_counter = 0;
+		}
+		else if (di->current_mA < -5) {
+			if (di->charge_status != BATTERY_STATUS_DISCHARGING)
+				printk(KERN_WARNING "%s: not enough power to "
+				       "charge\n", di->bi->name);
+			di->charge_status = BATTERY_STATUS_DISCHARGING;
+			di->full_counter = 0;
+		}
+		else if (di->current_mA < 10 &&
+		            di->charge_status != BATTERY_STATUS_FULL) {
+
+			/* Don't consider the battery to be full unless
+			 * we've seen the current < 10 mA at least two
+			 * consecutive times. */
+
+			di->full_counter++;
+
+			if (di->full_counter < 2)
+				di->charge_status = BATTERY_STATUS_CHARGING;
+			else {
+				unsigned char acr[2];
+
+				acr[0] = (di->full_active_mAh * 4) >> 8;
+				acr[1] = (di->full_active_mAh * 4) & 0xff;
+
+				if (w1_ds2760_write(di->w1_dev, acr,
+				    DS2760_CURRENT_ACCUM_MSB, 2) < 2)
+					printk(KERN_ERR "ACR reset failed\n");
+				di->charge_status = BATTERY_STATUS_FULL;
+			}
+		}
+	}
+	else {
+		di->charge_status = BATTERY_STATUS_DISCHARGING;
+		di->full_counter = 0;
+	}
+
+	if (di->charge_status != old_charge_status)
+		battery_status_changed(&di->batt_cdev);
+
+	return;
+}
+
+static int ds2760_battery_match_callback(struct device *dev, void *data)
+{
+	struct w1_slave *sl;
+
+	if (!(dev->driver && dev->driver->name &&
+	     (strcmp(dev->driver->name, "w1_slave_driver") == 0)))
+		return 0;
+
+	sl = container_of(dev, struct w1_slave, dev);
+
+	/* DS2760 w1 slave device names begin with the family number 0x30. */
+	if (strncmp(sl->name, "30-", 3) != 0)
+		return 0;
+
+	return 1;
+}
+
+static void ds2760_battery_work(struct work_struct *work)
+{
+	struct ds2760_device_info *di = container_of(work,
+		struct ds2760_device_info, monitor_work.work);
+	struct bus_type *bus;
+	int interval = HZ * 60;
+
+	if (!di->w1_dev) {
+		/* Get the battery w1 slave device. */
+		bus = find_bus("w1");
+		if (bus)
+			di->w1_dev = bus_find_device(bus, NULL, NULL,
+			                   ds2760_battery_match_callback);
+
+		if (!di->w1_dev) {
+			pr_debug("%s: no dev found\n", __FUNCTION__);
+			interval = HZ * 10;
+			goto again_please;
+		}
+		pr_debug("%s: dev found\n", __FUNCTION__);
+	}
+
+	ds2760_battery_update_status(di);
+
+again_please:
+	queue_delayed_work(di->monitor_wqueue, &di->monitor_work, interval);
+	return;
+}
+
+#define to_ds2760_device_info(x) container_of((x), struct ds2760_device_info, \
+                                              batt_cdev);
+
+static void ds2760_battery_external_power_changed(struct battery *bat)
+{
+	struct ds2760_device_info *di = to_ds2760_device_info(bat);
+	cancel_delayed_work(&di->monitor_work);
+	queue_delayed_work(di->monitor_wqueue, &di->monitor_work, HZ/10);
+	return;
+}
+
+#define ds2760_cdev_prop(x,y,z)                                             \
+        static int ds2760_battery_get_##y(struct battery *bat)              \
+        {                                                                   \
+                struct ds2760_device_info *di = to_ds2760_device_info(bat); \
+                if (x)                                                      \
+                        ds2760_battery_read_status(di);                     \
+                return di->z;                                               \
+        }
+
+ds2760_cdev_prop(0, max_voltage, bi->max_voltage);
+ds2760_cdev_prop(0, min_voltage, bi->min_voltage);
+ds2760_cdev_prop(1, voltage, voltage_mV);
+ds2760_cdev_prop(0, max_current, bi->max_current);
+ds2760_cdev_prop(0, min_current, bi->min_current);
+ds2760_cdev_prop(1, current, current_mA);
+ds2760_cdev_prop(1, max_capacity, full_active_mAh);
+ds2760_cdev_prop(1, min_capacity, empty_mAh);
+ds2760_cdev_prop(1, capacity, accum_current_mAh);
+ds2760_cdev_prop(1, temp, temp_C);
+ds2760_cdev_prop(0, status, charge_status);
+
+static int ds2760_battery_probe(struct platform_device *pdev)
+{
+	int retval = 0;
+	struct ds2760_device_info *di;
+	struct ds2760_platform_data *pdata;
+
+	di = kzalloc(sizeof(*di), GFP_KERNEL);
+	if (!di) {
+		retval = -ENOMEM;
+		goto di_alloc_failed;
+	}
+
+	platform_set_drvdata(pdev, di);
+
+	pdata = pdev->dev.platform_data;
+	di->bi = &pdata->battery_info;
+
+	di->batt_cdev.name             = di->bi->name;
+	di->batt_cdev.get_voltage      = ds2760_battery_get_voltage;
+	di->batt_cdev.get_min_voltage  = ds2760_battery_get_min_voltage;
+	di->batt_cdev.get_max_voltage  = ds2760_battery_get_max_voltage;
+	di->batt_cdev.get_current      = ds2760_battery_get_current;
+	di->batt_cdev.get_min_current  = ds2760_battery_get_min_current;
+	di->batt_cdev.get_max_current  = ds2760_battery_get_max_current;
+	di->batt_cdev.get_capacity     = ds2760_battery_get_capacity;
+	di->batt_cdev.get_min_capacity = ds2760_battery_get_min_capacity;
+	di->batt_cdev.get_max_capacity = ds2760_battery_get_max_capacity;
+	di->batt_cdev.get_temp         = ds2760_battery_get_temp;
+	di->batt_cdev.get_status       = ds2760_battery_get_status;
+	di->batt_cdev.external_power_changed =
+	                          ds2760_battery_external_power_changed;
+
+	di->charge_status = BATTERY_STATUS_UNKNOWN;
+
+	retval = battery_register(&pdev->dev, &di->batt_cdev);
+	if (retval) {
+		printk(KERN_ERR "Failed to register class dev for %s",
+		       pdev->name);
+		goto batt_cdev_failed;
+	}
+
+	INIT_DELAYED_WORK(&di->monitor_work, ds2760_battery_work);
+	di->monitor_wqueue = create_singlethread_workqueue("ds2760_mon");
+	if (!di->monitor_wqueue) {
+		retval = -ESRCH;
+		goto workqueue_failed;
+	}
+	queue_delayed_work(di->monitor_wqueue, &di->monitor_work, HZ * 1);
+
+	goto success;
+
+workqueue_failed:
+	battery_unregister(&di->batt_cdev);
+batt_cdev_failed:
+	kfree(di);
+di_alloc_failed:
+success:
+	return retval;
+}
+
+static int ds2760_battery_remove(struct platform_device *pdev)
+{
+	struct ds2760_device_info *di = platform_get_drvdata(pdev);
+
+	cancel_rearming_delayed_workqueue(di->monitor_wqueue,
+	                                  &di->monitor_work);
+	destroy_workqueue(di->monitor_wqueue);
+	battery_unregister(&di->batt_cdev);
+	if (di->w1_dev)
+		put_device(di->w1_dev);
+
+	return 0;
+}
+
+#ifdef CONFIG_PM
+static int ds2760_battery_suspend(struct platform_device *pdev,
+                                  pm_message_t state)
+{
+	struct ds2760_device_info *di = platform_get_drvdata(pdev);
+
+	di->charge_status = BATTERY_STATUS_UNKNOWN;
+	battery_status_changed(&di->batt_cdev);
+
+	return 0;
+}
+
+static int ds2760_battery_resume(struct platform_device *pdev)
+{
+	struct ds2760_device_info *di = platform_get_drvdata(pdev);
+
+	di->charge_status = BATTERY_STATUS_UNKNOWN;
+	battery_status_changed(&di->batt_cdev);
+
+	cancel_delayed_work(&di->monitor_work);
+	queue_delayed_work(di->monitor_wqueue, &di->monitor_work, HZ);
+
+	return 0;
+}
+#endif /* CONFIG_PM */
+
+static struct platform_driver ds2760_battery_driver = {
+	.driver = {
+		.name = "ds2760-battery",
+	},
+	.probe	  = ds2760_battery_probe,
+	.remove   = ds2760_battery_remove,
+	#ifdef CONFIG_PM
+	.suspend  = ds2760_battery_suspend,
+	.resume	  = ds2760_battery_resume,
+	#endif
+};
+
+static int __init ds2760_battery_init(void)
+{
+	return platform_driver_register(&ds2760_battery_driver);
+}
+
+static void __exit ds2760_battery_exit(void)
+{
+	platform_driver_unregister(&ds2760_battery_driver);
+}
+
+module_init(ds2760_battery_init);
+module_exit(ds2760_battery_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Szabolcs Gyurko <szabolcs.gyurko@tlt.hu>, "
+              "Matt Reimer <mreimer@vpop.net>, "
+              "Anton Vorontsov <cbou@mail.ru>");
+MODULE_DESCRIPTION("ds2760 battery driver");
diff --git a/include/linux/ds2760_battery.h b/include/linux/ds2760_battery.h
new file mode 100644
index 0000000..2937a54
--- /dev/null
+++ b/include/linux/ds2760_battery.h
@@ -0,0 +1,32 @@
+/*
+ * Driver for batteries with DS2760 chips inside.
+ *
+ * Copyright (c) 2007 Anton Vorontsov
+ *               2004 Matt Reimer
+ *               2004 Szabolcs Gyurko
+ *
+ * Use consistent with the GNU GPL is permitted,
+ * provided that this copyright notice is
+ * preserved in its entirety in all copies and derived works.
+ *
+ * Author:  Anton Vorontsov <cbou@mail.ru>
+ *          February 2007
+ *
+ *          Matt Reimer <mreimer@vpop.net>
+ *          April 2004, 2005
+ *
+ *          Szabolcs Gyurko <szabolcs.gyurko@tlt.hu>
+ *          September 2004
+ */
+
+#ifndef __DS2760_BATTERY__
+#define __DS2760_BATTERY__
+
+#include <linux/battery.h>
+
+struct ds2760_platform_data {
+	/* Battery information and characteristics. */
+	struct battery_info battery_info;
+};
+
+#endif
-- 
1.5.0.5-dirty

Re: [PATCH 6/7] [RFC] ds2760 battery driver

[Anton Vorontsov]

On Thu, Apr 12, 2007 at 03:25:45AM +0400, Anton Vorontsov wrote:
> This is driver for batteries with ds2760 chip inside. Such batteries
> used in almost every HP iPaq and HTC PDAs/phones.

Changes:

- follow battery class changes (get rid of vast amount of macro-created
  functions).

- cleanups based on comments by Randy Dunlap.


Subject: [PATCH] [take2] ds2760 battery driver


Signed-off-by: Anton Vorontsov <cbou@mail.ru>
---
 drivers/battery/Kconfig          |    7 +
 drivers/battery/Makefile         |    1 +
 drivers/battery/ds2760_battery.c |  493 ++++++++++++++++++++++++++++++++++++++
 include/linux/ds2760_battery.h   |   32 +++
 4 files changed, 533 insertions(+), 0 deletions(-)
 create mode 100644 drivers/battery/ds2760_battery.c
 create mode 100644 include/linux/ds2760_battery.h

diff --git a/drivers/battery/Kconfig b/drivers/battery/Kconfig
index c386593..0c14ae0 100644
--- a/drivers/battery/Kconfig
+++ b/drivers/battery/Kconfig
@@ -8,4 +8,11 @@ config BATTERY
 	  Say Y here to enable generic battery status reporting in
 	  the /sys filesystem.
 
+config BATTERY_DS2760
+	tristate "DS2760 battery driver (HP iPAQ & others)"
+	depends on BATTERY && W1
+	select W1_SLAVE_DS2760
+	help
+	  Say Y here to enable support for batteries with ds2760 chip.
+
 endmenu
diff --git a/drivers/battery/Makefile b/drivers/battery/Makefile
index a2239cb..9902513 100644
--- a/drivers/battery/Makefile
+++ b/drivers/battery/Makefile
@@ -1 +1,2 @@
 obj-$(CONFIG_BATTERY)              += battery.o
+obj-$(CONFIG_BATTERY_DS2760)       += ds2760_battery.o
diff --git a/drivers/battery/ds2760_battery.c b/drivers/battery/ds2760_battery.c
new file mode 100644
index 0000000..d996994
--- /dev/null
+++ b/drivers/battery/ds2760_battery.c
@@ -0,0 +1,493 @@
+/*
+ * Driver for batteries with DS2760 chips inside.
+ *
+ * Copyright (c) 2007 Anton Vorontsov
+ *               2004 Matt Reimer
+ *               2004 Szabolcs Gyurko
+ *
+ * Use consistent with the GNU GPL is permitted,
+ * provided that this copyright notice is
+ * preserved in its entirety in all copies and derived works.
+ *
+ * Author:  Anton Vorontsov <cbou@mail.ru>
+ *          February 2007
+ *
+ *          Matt Reimer <mreimer@vpop.net>
+ *          April 2004, 2005
+ *
+ *          Szabolcs Gyurko <szabolcs.gyurko@tlt.hu>
+ *          September 2004
+ */
+
+#include <linux/module.h>
+#include <linux/param.h>
+#include <linux/jiffies.h>
+#include <linux/workqueue.h>
+#include <linux/pm.h>
+#include <linux/platform_device.h>
+#include <linux/ds2760_battery.h>
+
+#include "../w1/w1.h"
+#include "../w1/slaves/w1_ds2760.h"
+
+struct ds2760_device_info {
+	struct battery_info *bi;
+
+	/* DS2760 data, valid after calling ds2760_battery_read_status() */
+	unsigned long update_time;      /* jiffies when data read */
+	char raw[DS2760_DATA_SIZE];     /* raw DS2760 data */
+	int voltage_raw;                /* units of 4.88 mV */
+	int voltage_mV;                 /* units of mV */
+	int current_raw;                /* units of 0.625 mA */
+	int current_mA;                 /* units of mA */
+	int accum_current_raw;          /* units of 0.25 mAh */
+	int accum_current_mAh;          /* units of mAh */
+	int temp_raw;                   /* units of 0.125 C */
+	int temp_C;                     /* units of 0.1 C */
+	int rated_capacity;             /* units of mAh */
+	int rem_capacity;               /* percentage */
+	int full_active_mAh;            /* units of mAh */
+	int empty_mAh;                  /* units of mAh */
+	int life_min;                   /* units of minutes */
+	int charge_status;              /* BATTERY_STATUS_* */
+
+	int full_counter;
+	struct battery batt;
+	struct device *w1_dev;
+	struct workqueue_struct *monitor_wqueue;
+	struct delayed_work monitor_work;
+};
+
+static unsigned int cache_time = 1000;
+module_param(cache_time, uint, 0644);
+MODULE_PARM_DESC(cache_time, "cache time in milliseconds");
+
+/* Some batteries have their rated capacity stored a N * 10 mAh, while
+ * others use an index into this table. */
+static int rated_capacities[] = {
+	0,
+	920,        /* Samsung */
+	920,        /* BYD */
+	920,        /* Lishen */
+	920,        /* NEC */
+	1440,       /* Samsung */
+	1440,       /* BYD */
+	1440,       /* Lishen */
+	1440,       /* NEC */
+	2880,       /* Samsung */
+	2880,       /* BYD */
+	2880,       /* Lishen */
+	2880        /* NEC */
+};
+
+/* array is level at temps 0C, 10C, 20C, 30C, 40C
+ * temp is in Celsius */
+static int battery_interpolate(int array[], int temp)
+{
+	int index, dt;
+
+	if (temp <= 0)
+		return array[0];
+	if (temp >= 40)
+		return array[4];
+
+	index = temp / 10;
+	dt    = temp % 10;
+
+	return array[index] + (((array[index + 1] - array[index]) * dt) / 10);
+}
+
+static int ds2760_battery_read_status(struct ds2760_device_info *di)
+{
+	int ret, i, start, count, scale[5];
+
+	if (di->update_time && time_before(jiffies, di->update_time +
+	                                   msecs_to_jiffies(cache_time)))
+		return 0;
+
+	if (!di->w1_dev)
+		return 0;
+
+	/* The first time we read the entire contents of SRAM/EEPROM,
+	 * but after that we just read the interesting bits that change. */
+	if (di->update_time == 0) {
+		start = 0;
+		count = DS2760_DATA_SIZE;
+	}
+	else {
+		start = DS2760_VOLTAGE_MSB;
+		count = DS2760_TEMP_LSB - start + 1;
+	}
+
+	ret = w1_ds2760_read(di->w1_dev, di->raw + start, start, count);
+	if (ret != count) {
+		printk("call to w1_ds2760_read failed (0x%08x)\n",
+		       (unsigned int)di->w1_dev);
+		return 1;
+	}
+
+	di->update_time = jiffies;
+
+	/* DS2760 reports voltage in units of 4.88mV, but the battery class
+	 * reports in units of mV, so convert by multiplying by 4.875.
+	 * We approximate because integer math is cheap, and close enough. */
+	di->voltage_raw = (di->raw[DS2760_VOLTAGE_MSB] << 3) |
+	                  (di->raw[DS2760_VOLTAGE_LSB] >> 5);
+	di->voltage_mV = (di->voltage_raw * 5) - (di->voltage_raw / 8);
+
+	/* DS2760 reports current in signed units of 0.625mA, but the battery
+	 * class reports in units of mA, so convert by multiplying by 0.625. */
+	di->current_raw =
+	    (((signed char)di->raw[DS2760_CURRENT_MSB]) << 5) |
+	                  (di->raw[DS2760_CURRENT_LSB] >> 3);
+	di->current_mA = (di->current_raw / 2) + (di->current_raw / 8);
+
+	/* DS2760 reports accumulated current in signed units of 0.25mAh. */
+	di->accum_current_raw =
+	    (((signed char)di->raw[DS2760_CURRENT_ACCUM_MSB]) << 8) |
+	                   di->raw[DS2760_CURRENT_ACCUM_LSB];
+	di->accum_current_mAh = di->accum_current_raw / 4;
+
+	/* DS2760 reports temperature in signed units of 0.125C, but the
+	 * battery class reports in units of 1/10 C, so we convert by
+	 * multiplying by .125 * 10 = 1.25. */
+	di->temp_raw = (((signed char)di->raw[DS2760_TEMP_MSB]) << 3) |
+	                             (di->raw[DS2760_TEMP_LSB] >> 5);
+	di->temp_C = di->temp_raw + (di->temp_raw / 4);
+
+	/* At least some battery monitors (e.g. HP iPAQ) store the battery's
+	 * maximum rated capacity. */
+	if (di->raw[DS2760_RATED_CAPACITY] < ARRAY_SIZE(rated_capacities))
+		di->rated_capacity = rated_capacities[
+		        (unsigned int)di->raw[DS2760_RATED_CAPACITY]];
+	else
+		di->rated_capacity = di->raw[DS2760_RATED_CAPACITY] * 10;
+
+	/* Calculate the full level at the present temperature. */
+	di->full_active_mAh = di->raw[DS2760_ACTIVE_FULL] << 8 |
+	                      di->raw[DS2760_ACTIVE_FULL + 1];
+
+	scale[0] = di->raw[DS2760_ACTIVE_FULL] << 8 |
+	           di->raw[DS2760_ACTIVE_FULL + 1];
+	for (i = 1; i < 5; i++)
+		scale[i] = scale[i - 1] + di->raw[DS2760_ACTIVE_FULL + 2 + i];
+
+	di->full_active_mAh = battery_interpolate(scale, di->temp_C / 10);
+
+	/* Calculate the empty level at the present temperature. */
+	scale[4] = di->raw[DS2760_ACTIVE_EMPTY + 4];
+	for (i = 3; i >= 0; i--)
+		scale[i] = scale[i + 1] + di->raw[DS2760_ACTIVE_EMPTY + i];
+
+	di->empty_mAh = battery_interpolate(scale, di->temp_C / 10);
+
+	/* From Maxim Application Note 131: remaining capacity =
+	 * ((ICA - Empty Value) / (Full Value - Empty Value)) x 100% */
+	di->rem_capacity = ((di->accum_current_mAh - di->empty_mAh) * 100) /
+	                    (di->full_active_mAh - di->empty_mAh);
+
+	if (di->rem_capacity < 0)
+		di->rem_capacity = 0;
+	if (di->rem_capacity > 100)
+		di->rem_capacity = 100;
+
+	if (di->current_mA)
+		di->life_min = -((di->accum_current_mAh - di->empty_mAh) *
+		                 60) / di->current_mA;
+	else
+		di->life_min = 0;
+
+	return 0;
+}
+
+static void ds2760_battery_update_status(struct ds2760_device_info *di)
+{
+	int old_charge_status = di->charge_status;
+
+	ds2760_battery_read_status(di);
+
+	if (di->charge_status == BATTERY_STATUS_UNKNOWN)
+		di->full_counter = 0;
+
+	if (battery_is_external_power_supplied(&di->batt)) {
+		if (di->current_mA > 10) {
+			di->charge_status = BATTERY_STATUS_CHARGING;
+			di->full_counter = 0;
+		}
+		else if (di->current_mA < -5) {
+			if (di->charge_status != BATTERY_STATUS_DISCHARGING)
+				printk(KERN_WARNING "%s: not enough power to "
+				       "charge\n", di->bi->name);
+			di->charge_status = BATTERY_STATUS_DISCHARGING;
+			di->full_counter = 0;
+		}
+		else if (di->current_mA < 10 &&
+		            di->charge_status != BATTERY_STATUS_FULL) {
+
+			/* Don't consider the battery to be full unless
+			 * we've seen the current < 10 mA at least two
+			 * consecutive times. */
+
+			di->full_counter++;
+
+			if (di->full_counter < 2)
+				di->charge_status = BATTERY_STATUS_CHARGING;
+			else {
+				unsigned char acr[2];
+
+				acr[0] = (di->full_active_mAh * 4) >> 8;
+				acr[1] = (di->full_active_mAh * 4) & 0xff;
+
+				if (w1_ds2760_write(di->w1_dev, acr,
+				    DS2760_CURRENT_ACCUM_MSB, 2) < 2)
+					printk(KERN_ERR "ACR reset failed\n");
+				di->charge_status = BATTERY_STATUS_FULL;
+			}
+		}
+	}
+	else {
+		di->charge_status = BATTERY_STATUS_DISCHARGING;
+		di->full_counter = 0;
+	}
+
+	if (di->charge_status != old_charge_status)
+		battery_status_changed(&di->batt);
+
+	return;
+}
+
+static int ds2760_battery_match_callback(struct device *dev, void *data)
+{
+	struct w1_slave *sl;
+
+	if (!(dev->driver && dev->driver->name &&
+	     (strcmp(dev->driver->name, "w1_slave_driver") == 0)))
+		return 0;
+
+	sl = container_of(dev, struct w1_slave, dev);
+
+	/* DS2760 w1 slave device names begin with the family number 0x30. */
+	if (strncmp(sl->name, "30-", 3) != 0)
+		return 0;
+
+	return 1;
+}
+
+static void ds2760_battery_work(struct work_struct *work)
+{
+	struct ds2760_device_info *di = container_of(work,
+		struct ds2760_device_info, monitor_work.work);
+	struct bus_type *bus;
+	int interval = HZ * 60;
+
+	pr_debug("%s\n", __FUNCTION__);
+
+	if (!di->w1_dev) {
+		/* Get the battery w1 slave device. */
+		bus = find_bus("w1");
+		if (bus)
+			di->w1_dev = bus_find_device(bus, NULL, NULL,
+			                   ds2760_battery_match_callback);
+
+		if (!di->w1_dev) {
+			pr_debug("%s: no dev found\n", __FUNCTION__);
+			interval = HZ * 10;
+			goto again_please;
+		}
+		pr_debug("%s: dev found\n", __FUNCTION__);
+	}
+
+	ds2760_battery_update_status(di);
+
+again_please:
+	queue_delayed_work(di->monitor_wqueue, &di->monitor_work, interval);
+	return;
+}
+
+#define to_ds2760_device_info(x) container_of((x), struct ds2760_device_info, \
+                                              batt);
+
+static void ds2760_battery_external_power_changed(struct battery *bat)
+{
+	struct ds2760_device_info *di = to_ds2760_device_info(bat);
+
+	pr_debug("%s\n", __FUNCTION__);
+
+	cancel_delayed_work(&di->monitor_work);
+	queue_delayed_work(di->monitor_wqueue, &di->monitor_work, HZ/10);
+
+	return;
+}
+
+static void *ds2760_battery_get_property(struct battery *bat,
+                                         enum battery_property bp)
+{
+	struct ds2760_device_info *di = to_ds2760_device_info(bat);
+
+	switch (bp) {
+	case BATTERY_PROP_MAX_VOLTAGE:
+		return &di->bi->max_voltage;
+	case BATTERY_PROP_MIN_VOLTAGE:
+		return &di->bi->min_voltage;
+	case BATTERY_PROP_VOLTAGE:
+		ds2760_battery_read_status(di);
+		return &di->voltage_mV;
+	case BATTERY_PROP_MAX_CURRENT:
+		return &di->bi->max_current;
+	case BATTERY_PROP_CURRENT:
+		ds2760_battery_read_status(di);
+		return &di->current_mA;
+	case BATTERY_PROP_MAX_CHARGE:
+		ds2760_battery_read_status(di);
+		return &di->full_active_mAh;
+	case BATTERY_PROP_MIN_CHARGE:
+		ds2760_battery_read_status(di);
+		return &di->empty_mAh;
+	case BATTERY_PROP_CHARGE:
+		ds2760_battery_read_status(di);
+		return &di->accum_current_mAh;
+	case BATTERY_PROP_TEMP:
+		ds2760_battery_read_status(di);
+		return &di->temp_C;
+	case BATTERY_PROP_STATUS:
+		return &di->charge_status;
+	default:
+		return NULL;
+	};
+}
+
+static int ds2760_battery_properties[] = {
+	BATTERY_PROP_MAX_VOLTAGE,
+	BATTERY_PROP_MIN_VOLTAGE,
+	BATTERY_PROP_VOLTAGE,
+	BATTERY_PROP_MAX_CURRENT,
+	BATTERY_PROP_CURRENT,
+	BATTERY_PROP_MAX_CHARGE,
+	BATTERY_PROP_MIN_CHARGE,
+	BATTERY_PROP_CHARGE,
+	BATTERY_PROP_TEMP,
+	BATTERY_PROP_STATUS,
+};
+
+static int ds2760_battery_probe(struct platform_device *pdev)
+{
+	int retval = 0;
+	struct ds2760_device_info *di;
+	struct ds2760_platform_data *pdata;
+
+	di = kzalloc(sizeof(*di), GFP_KERNEL);
+	if (!di) {
+		retval = -ENOMEM;
+		goto di_alloc_failed;
+	}
+
+	platform_set_drvdata(pdev, di);
+
+	pdata = pdev->dev.platform_data;
+	di->bi = &pdata->battery_info;
+
+	di->batt.name           = di->bi->name;
+	di->batt.properties     = ds2760_battery_properties;
+	di->batt.num_properties = ARRAY_SIZE(ds2760_battery_properties);
+	di->batt.get_property   = ds2760_battery_get_property;
+	di->batt.external_power_changed =
+	                          ds2760_battery_external_power_changed;
+
+	di->charge_status = BATTERY_STATUS_UNKNOWN;
+
+	retval = battery_register(&pdev->dev, &di->batt);
+	if (retval) {
+		printk(KERN_ERR "Failed to register class dev for %s",
+		       pdev->name);
+		goto batt_failed;
+	}
+
+	INIT_DELAYED_WORK(&di->monitor_work, ds2760_battery_work);
+	di->monitor_wqueue = create_singlethread_workqueue("ds2760_mon");
+	if (!di->monitor_wqueue) {
+		retval = -ESRCH;
+		goto workqueue_failed;
+	}
+	queue_delayed_work(di->monitor_wqueue, &di->monitor_work, HZ * 1);
+
+	goto success;
+
+workqueue_failed:
+	battery_unregister(&di->batt);
+batt_failed:
+	kfree(di);
+di_alloc_failed:
+success:
+	return retval;
+}
+
+static int ds2760_battery_remove(struct platform_device *pdev)
+{
+	struct ds2760_device_info *di = platform_get_drvdata(pdev);
+
+	cancel_rearming_delayed_workqueue(di->monitor_wqueue,
+	                                  &di->monitor_work);
+	destroy_workqueue(di->monitor_wqueue);
+	battery_unregister(&di->batt);
+	if (di->w1_dev)
+		put_device(di->w1_dev);
+
+	return 0;
+}
+
+#ifdef CONFIG_PM
+static int ds2760_battery_suspend(struct platform_device *pdev,
+                                  pm_message_t state)
+{
+	struct ds2760_device_info *di = platform_get_drvdata(pdev);
+
+	di->charge_status = BATTERY_STATUS_UNKNOWN;
+	battery_status_changed(&di->batt);
+
+	return 0;
+}
+
+static int ds2760_battery_resume(struct platform_device *pdev)
+{
+	struct ds2760_device_info *di = platform_get_drvdata(pdev);
+
+	di->charge_status = BATTERY_STATUS_UNKNOWN;
+	battery_status_changed(&di->batt);
+
+	cancel_delayed_work(&di->monitor_work);
+	queue_delayed_work(di->monitor_wqueue, &di->monitor_work, HZ);
+
+	return 0;
+}
+#endif /* CONFIG_PM */
+
+static struct platform_driver ds2760_battery_driver = {
+	.driver = {
+		.name = "ds2760-battery",
+	},
+	.probe	  = ds2760_battery_probe,
+	.remove   = ds2760_battery_remove,
+#ifdef CONFIG_PM
+	.suspend  = ds2760_battery_suspend,
+	.resume	  = ds2760_battery_resume,
+#endif
+};
+
+static int __init ds2760_battery_init(void)
+{
+	return platform_driver_register(&ds2760_battery_driver);
+}
+
+static void __exit ds2760_battery_exit(void)
+{
+	platform_driver_unregister(&ds2760_battery_driver);
+}
+
+module_init(ds2760_battery_init);
+module_exit(ds2760_battery_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Szabolcs Gyurko <szabolcs.gyurko@tlt.hu>, "
+              "Matt Reimer <mreimer@vpop.net>, "
+              "Anton Vorontsov <cbou@mail.ru>");
+MODULE_DESCRIPTION("ds2760 battery driver");
diff --git a/include/linux/ds2760_battery.h b/include/linux/ds2760_battery.h
new file mode 100644
index 0000000..2937a54
--- /dev/null
+++ b/include/linux/ds2760_battery.h
@@ -0,0 +1,32 @@
+/*
+ * Driver for batteries with DS2760 chips inside.
+ *
+ * Copyright (c) 2007 Anton Vorontsov
+ *               2004 Matt Reimer
+ *               2004 Szabolcs Gyurko
+ *
+ * Use consistent with the GNU GPL is permitted,
+ * provided that this copyright notice is
+ * preserved in its entirety in all copies and derived works.
+ *
+ * Author:  Anton Vorontsov <cbou@mail.ru>
+ *          February 2007
+ *
+ *          Matt Reimer <mreimer@vpop.net>
+ *          April 2004, 2005
+ *
+ *          Szabolcs Gyurko <szabolcs.gyurko@tlt.hu>
+ *          September 2004
+ */
+
+#ifndef __DS2760_BATTERY__
+#define __DS2760_BATTERY__
+
+#include <linux/battery.h>
+
+struct ds2760_platform_data {
+	/* Battery information and characteristics. */
+	struct battery_info battery_info;
+};
+
+#endif
-- 
1.5.0.5-dirty

Re: [PATCH 6/7] [RFC] ds2760 battery driver

[Pavel Machek]

Hi!

> This is driver for batteries with ds2760 chip inside. Such batteries
> used in almost every HP iPaq and HTC PDAs/phones.

Looks nice to me. It even knows about dependency between temperature
and remaining power :-).


> +	di->update_time = jiffies;
> +
> +	/* DS2760 reports voltage in units of 4.88mV, but the battery class
> +	 * reports in units of mV, so convert by multiplying by 4.875.
> +	 * We approximate because integer math is cheap, and close enough. */
> +	di->voltage_raw = (di->raw[DS2760_VOLTAGE_MSB] << 3) |
> +	                  (di->raw[DS2760_VOLTAGE_LSB] >> 5);
> +	di->voltage_mV = (di->voltage_raw * 5) - (di->voltage_raw / 8);

Hmm, not sure if such tricks re really worth it... should not compiler
be doing this?


> +	/* Calculate the empty level at the present temperature. */
> +	scale[4] = di->raw[DS2760_ACTIVE_EMPTY + 4];
> +	for (i = 3; i >= 0; i--)
> +		scale[i] = scale[i + 1] + di->raw[DS2760_ACTIVE_EMPTY + i];
> +
> +	di->empty_mAh = battery_interpolate(scale, di->temp_C / 10);

Wow.

> +static struct platform_driver ds2760_battery_driver = {
> +	.driver = {
> +		.name = "ds2760-battery",
> +	},
> +	.probe	  = ds2760_battery_probe,
> +	.remove   = ds2760_battery_remove,
> +	#ifdef CONFIG_PM
> +	.suspend  = ds2760_battery_suspend,
> +	.resume	  = ds2760_battery_resume,
> +	#endif

I thought ifdefs need to be at column 0?

							Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

Re: [PATCH 6/7] [RFC] ds2760 battery driver

[Matt Reimer]

On 4/15/07, Pavel Machek <pavel@ucw.cz> wrote:
> > +     di->update_time = jiffies;
> > +
> > +     /* DS2760 reports voltage in units of 4.88mV, but the battery class
> > +      * reports in units of mV, so convert by multiplying by 4.875.
> > +      * We approximate because integer math is cheap, and close enough. */
> > +     di->voltage_raw = (di->raw[DS2760_VOLTAGE_MSB] << 3) |
> > +                       (di->raw[DS2760_VOLTAGE_LSB] >> 5);
> > +     di->voltage_mV = (di->voltage_raw * 5) - (di->voltage_raw / 8);
>
> Hmm, not sure if such tricks re really worth it... should not compiler
> be doing this?

The shifts (<< 3 and >> 5) are just to get the bits reassembled in the
right positions. The multiplication by 5 and subtracting 1/8 is
because (AFAIK) we can't do floating point multiplication in the
kernel. I'm open to suggestions.

> > +     /* Calculate the empty level at the present temperature. */
> > +     scale[4] = di->raw[DS2760_ACTIVE_EMPTY + 4];
> > +     for (i = 3; i >= 0; i--)
> > +             scale[i] = scale[i + 1] + di->raw[DS2760_ACTIVE_EMPTY + i];
> > +
> > +     di->empty_mAh = battery_interpolate(scale, di->temp_C / 10);
>
> Wow.

Yeah, mea culpa. I don't like its obtuseness either, and haven't
revisited it since I got it working. Basically the battery has an
array stored in its EEPROM that represents the empty level at various
temperature thresholds. What makes this complicated is that the array
does not contain all absolute values; just the first is absolute, and
the others are relative to it, in reverse order. The above code
converts it to an array of absolute values from low to high. I'm open
to suggestions about this one too.

Matt

Re: [PATCH 6/7] [RFC] ds2760 battery driver

[Anton Vorontsov]

On Mon, Apr 16, 2007 at 12:14:27PM -0700, Matt Reimer wrote:
>  On 4/15/07, Pavel Machek <pavel@ucw.cz> wrote:
> > > +     di->update_time = jiffies;
> > > +
> > > +     /* DS2760 reports voltage in units of 4.88mV, but the battery class
> > > +      * reports in units of mV, so convert by multiplying by 4.875.
> > > +      * We approximate because integer math is cheap, and close enough. 
> > */
> > > +     di->voltage_raw = (di->raw[DS2760_VOLTAGE_MSB] << 3) |
> > > +                       (di->raw[DS2760_VOLTAGE_LSB] >> 5);
> > > +     di->voltage_mV = (di->voltage_raw * 5) - (di->voltage_raw / 8);
> >
> > Hmm, not sure if such tricks re really worth it... should not compiler
> > be doing this?
> 
>  The shifts (<< 3 and >> 5) are just to get the bits reassembled in the
>  right positions. The multiplication by 5 and subtracting 1/8 is
>  because (AFAIK) we can't do floating point multiplication in the
>  kernel. I'm open to suggestions.

Because we are in micro world now, divisions already replaced by
multiplication. I.e.

        /* DS2760 reports voltage in units of 4.88mV, but the battery class
         * reports in units of uV, so convert by multiplying by 4880. */
        di->voltage_raw = (di->raw[DS2760_VOLTAGE_MSB] << 3) |
                          (di->raw[DS2760_VOLTAGE_LSB] >> 5);
        di->voltage_uV = di->voltage_raw * 4880;

As a side effect, now we're not losing any precision. :-)

> > > +     /* Calculate the empty level at the present temperature. */
> > > +     scale[4] = di->raw[DS2760_ACTIVE_EMPTY + 4];
> > > +     for (i = 3; i >= 0; i--)
> > > +             scale[i] = scale[i + 1] + di->raw[DS2760_ACTIVE_EMPTY + i];
> > > +
> > > +     di->empty_mAh = battery_interpolate(scale, di->temp_C / 10);
> >
> > Wow.
> 
>  Yeah, mea culpa. I don't like its obtuseness either, and haven't
>  revisited it since I got it working. Basically the battery has an
>  array stored in its EEPROM that represents the empty level at various
>  temperature thresholds. What makes this complicated is that the array
>  does not contain all absolute values; just the first is absolute, and
>  the others are relative to it, in reverse order. The above code
>  converts it to an array of absolute values from low to high. I'm open
>  to suggestions about this one too.

By the way. Matt, you're more familiar with ds2760 specs, could you
enlighten me about "* 4" in this snippet?

>       acr[0] = (di->full_active_mAh * 4) >> 8;
                                      ^^^
>       acr[1] = (di->full_active_mAh * 4) & 0xff;
                                      ^^^
>       if (w1_ds2760_write(di->w1_dev, acr,
>                           DS2760_CURRENT_ACCUM_MSB, 2) < 2)
>              printk(KERN_ERR "ACR reset failed\n");


>  Matt

Thanks!

-- 
Anton Vorontsov
email: cbou@mail.ru
backup email: ya-cbou@yandex.ru
irc://irc.freenode.org/bd2

Re: [PATCH 6/7] [RFC] ds2760 battery driver

[Matt Reimer]

On 4/16/07, Anton Vorontsov <cbou@mail.ru> wrote:
> On Mon, Apr 16, 2007 at 12:14:27PM -0700, Matt Reimer wrote:
> >  The shifts (<< 3 and >> 5) are just to get the bits reassembled in the
> >  right positions. The multiplication by 5 and subtracting 1/8 is
> >  because (AFAIK) we can't do floating point multiplication in the
> >  kernel. I'm open to suggestions.
>
> Because we are in micro world now, divisions already replaced by
> multiplication. I.e.
>
>         /* DS2760 reports voltage in units of 4.88mV, but the battery class
>          * reports in units of uV, so convert by multiplying by 4880. */
>         di->voltage_raw = (di->raw[DS2760_VOLTAGE_MSB] << 3) |
>                           (di->raw[DS2760_VOLTAGE_LSB] >> 5);
>         di->voltage_uV = di->voltage_raw * 4880;
>
> As a side effect, now we're not losing any precision. :-)

That's a good way to solve the problem. :-)

> By the way. Matt, you're more familiar with ds2760 specs, could you
> enlighten me about "* 4" in this snippet?
>
> >       acr[0] = (di->full_active_mAh * 4) >> 8;
>                                       ^^^
> >       acr[1] = (di->full_active_mAh * 4) & 0xff;
>                                       ^^^
> >       if (w1_ds2760_write(di->w1_dev, acr,
> >                           DS2760_CURRENT_ACCUM_MSB, 2) < 2)
> >              printk(KERN_ERR "ACR reset failed\n");

The accumulated current register (acr) value is in units of 0.25 mAh,
so we have to multiply by 4 to convert from units of 1 mAh to 0.25
mAh.

Thanks for all your work on this Anton.

Matt

Re: [PATCH 6/7] [RFC] ds2760 battery driver

[Pavel Machek]

Hi!

> >> +     /* Calculate the empty level at the present temperature. */
> >> +     scale[4] = di->raw[DS2760_ACTIVE_EMPTY + 4];
> >> +     for (i = 3; i >= 0; i--)
> >> +             scale[i] = scale[i + 1] + di->raw[DS2760_ACTIVE_EMPTY + i];
> >> +
> >> +     di->empty_mAh = battery_interpolate(scale, di->temp_C / 10);
> >
> >Wow.
> 
> Yeah, mea culpa. I don't like its obtuseness either, and haven't
> revisited it since I got it working. Basically the battery has an

No, I actually like the fact that someone cared enough about
temperature's influence on li-ion.
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html