Device Driver
*************
Latest Linux device driver for bq27xxx single-cell gauges is available here:
https://github.com/aneeshv/linux-bq27xxx.git
branch: master

Driver file:
https://github.com/aneeshv/linux-bq27xxx/blob/master/drivers/power/bq27x00_battery.c

Enabling the driver on your platform:
The following patch demonstrates how bq274xx support was added on
Beaglebone Black assuming it is connected to I2C1 bus.
https://github.com/aneeshv/linux-bq27xxx/commit/41d350fc48643e82982c4ad93f20878f83e3408d
Replace "bq274xx" with the correct devices for your platform. The list of
devices currently supported by the driver can be found in:

https://github.com/aneeshv/linux-bq27xxx/blob/master/drivers/power/bq27x00_battery.c

Look for this array in the driver to see the list of currenlty supported
devices:
static const struct i2c_device_id bq27x00_id[] = {

Support for ROM-based Gauges (bq274xx/bq27621):
===============================================
The above driver supports some of the special requirements for ROM-based
gauges such as bq27421 and bq27621.

What it does:
In addition to the regular reporting functions (Voltage(), Current(), SOC()
etc.) this driver has APIs for reading and writing the DM of the gauge.
These APIs are in turn used for initializing the DM of ROM based gauges.
The initialization happens at startup(about ~65s into the the startup).
After startup we poll the status of ITPOR every 6 minutes and repeat the
DM initialization if it’s set. The polling happens along with the polling
of other parameters such as Current(), SOC() etc and the period for this
polling loop is customizable. The registers to initialized in the DM may
be specified in the code in an array like this:

static struct dm_reg bq276xx_dm_regs[] = {
	{64, 2, 1, 0x2C},	/* Op Config B */
	{82, 0, 2, 1000},	/* Qmax */
	{82, 2, 1, 0x81},	/* Load Select */
	{82, 3, 2, 1340},	/* Design Capacity */
	{82, 5, 2, 3700},	/* Design Energy */
	{82, 9, 2, 3250},	/* Terminate Voltage */
	{82, 20, 2, 110},	/* Taper rate */
};

What it doesn’t:
It doesn’t have a mechanism to save and restore Ra values and Qmax as
suggested in the Quick Start Guide of bq274xx devices.  This means it will
reload default values every time the battery is inserted.

bqtool
******
bqtool is an Android commandline utility for programming, monitoring,
and debugging TI's bq27xxx family of single-cell gas gauges. Currently
it supports only bqfs flashing. However, more features will be added
in the future. Although bqtool is created for Android it can be easily
ported for any Linux system.

It's available here:
https://github.com/aneeshv/bqtool.git
branch: master

Commands supported:
--flash :
	bqtool --flash <bqfs file|dffs file>
	Eg: bqtool --flash /system/bin/bq27520_v302.bqfs

For more details see bqtool's README:
https://github.com/aneeshv/bqtool/blob/master/README