Re: [PATCH v2 2/2] mfd: Add initial synology microp driver

[Markus Probst]

On Mon, 2026-03-09 at 14:32 +0100, Danilo Krummrich wrote:
> On Mon Mar 9, 2026 at 1:52 PM CET, Markus Probst wrote:
> > Yes. I will split it into multiple drivers using the aux bus in the
> > next revision.
> 
> Independent of the other discussion whether this belongs into the kernel in the
> first place, reading over the cover letter and commit message I understood the
> following.
> 
>   "Synology uses a microcontroller in their NAS devices connected to a serial
>   port [...]" controlling LEDs, fan speeds, a beeper, etc.
> 
>   I.e. it muliplexes several physical functions that belong to different
>   subsystems, such as hwmon, input, etc. over a single serial port.
> 
> This sounds like a textbook candidate for MFD to me.
> 
> I.e. there is a very loose coupling of the different functions that make up for
> entirely independent drivers, except that they share the same serial port
> connection.
> 
> Whereas the auxiliary bus is more for very complicated devices to be broken down
> into more managable (sometimes optional) sub-domains, where the corresponding
> drivers usually have driver specific APIs to interact with each other.
> 
> - Danilo

QNAP and Synology do things very similarly.
There is already a driver for QNAP devices:

drivers/mfd/qnap-mcu.c
drivers/leds/leds-qnap-mcu.c
drivers/input/misc/qnap-mcu-input.c
drivers/hwmon/qnap-mcu-hwmon.c
drivers/nvmem/qnap-mcu-eeprom.c

drivers/power/reset/qnap-poweroff.c (this one is not part of the mfd)

and I try to implement the equivalent for Synology devices.
Given its a MFD I would assume the same applies to this driver?

Thanks
- Markus Probst

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