Re: [PATCH 1/5] dt-bindings: power: bq27xxx: document bq27z746

[Krzysztof Kozlowski <krzk@kernel.org>]

On 17/08/2026 17:00, Henrik Grimler wrote:
> Hi Krzysztof, 
> 
> Thanks for the comment!
> 
> On Mon, 2026-08-17 at 09:50 +0200, Krzysztof Kozlowski wrote:
>> On Tue, Aug 11, 2026 at 01:47:43PM +0200, Henrik Grimler wrote:
>>> Add compatible for Texas Instruments bq27z746 fuel gauge, which is
>>> similar to its sibling bqz27561, but with more protection
>>> functionality.
>>
>> "More" means superset? Driver code says it is compatible, so this has to
>> be explained 
> 
> I will update the commit message to explain the differences. Main
> difference is that bq27z746 has integrated protection logic, and can
> control external MOSFETs to stop charging/discharging if an issue is
> detected (like overcurrent or overvoltage), or to keep the rest of the
> system fully powered off in shipping mode. bq27z561 does not have such
> protection circuitry, so best it can do if it detects issues is to send
> an interrupt to some other component.
> 
> The standard register map is almost identical between the devices.
> bq27z561 has 6 extra registers at the end that bq27z746 lacks though,
> which I missed when comparing the TRMs the first time (so bq27z561 map
> is a superset of bq27z746's). Neither of these extra registers are
> supported/handled by the Linux driver through. I will update all the
> commit messages for v2 to clarify.
> 
> There are also additional "ManufacturerAccess" registers where there
> are some more differences between bq27z561 and bq27z746 mostly related
> to the above mentioned MOSFET control, but the current Linux driver
> does not read or handle any "ManufacturerAccess" register. One of my
> colleagues has sent a patch to add support for reading PROP_MODEL_NAME
> from these additional registers for bq27z561 though [1]. This model
> name register is the same for bq27z561 and bq27z746.
> 
> In summary the chips have differences, but I expect it will be fine for
> the driver to use same regs and props for bq27z746 and bq27z561.

Well, superset is exactly what compatibility is about.

Best regards,
Krzysztof