G'day Karl On 29/04/2016 03:15, Karl-Heinz Schneider wrote:
I have written an Kernel driver for the LTC1760 which is basically an charger which can handle 2 batteries. Datasheet can be found at http://www.linear.com/product/LTC1760
They're nice chips.
However, the device has one speciality: Hence it handles two smart batteries, which are expected to sit on I2C address 0x0b, it implements an i2c mux. As the device does so, my driver does also (using i2c_add_mux_adapter() call). Further more, Linux already ships with an driver capable to talk to these smart battery chips, namely "sbs-battery". I currently using device tree to bind the LTC1760 to the smbus it sits on and further to define the i2c-lines it implements as well as the batteries sitting on the two muxed lines. Would you say this approach is technically right? The LTC expects SBS compliant batteries connected to it, which implies a standard minimal interface. But binding the batteries via device tree gives the user the freedom to specify a more specialized driver. On the other hand one could argue that if the LTC is present, also batteries are (potentially) present and the LTC driver is responsible to read the related registers and provide proper PM attributes. Personally I don't like to rewrite or copy code wich works just fine...
I've been writing a driver for the same chip :). My system has 2 ltc1760 for a total of 4 batteries. Haven't completed it as yet so hadn't posted, but got it talking to the batteries. I implemented an I2c mux in the driver and just attached two sbs-battery's to it in the device tree. I think the mux is the way to go, simple and reuses existing code. The sbs-battery driver needs a couple of gpio pins to indicate battery presence, so I was thinking of implementing these in the ltc1760 as gpio pins. Not sure what the bext approach is here. FYI, if you didn't find it there is an acpi only driver for the ltc1760 in the kernel. But I could see a way to make it work with device trees. It enumerates it's own batteries. I have found the ltc1760 doesn't work to well with some i2c masters. Currently using the bit bang i2c bus driver as that was the most reliable. The designware controller kept locking up. -- Regards Phil Reid -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
