Re: [PATCH v7 9/9] misc: add FPC202 dual port controller driver

[Romain Gantois]

Hello Wolfram,

On jeudi 20 février 2025 13:09:03 heure normale d’Europe centrale Wolfram Sang 
wrote:
> > as this is a i2c_driver, why isn't it in drivers/i2c/ somewhere?  Why
> > misc?
> 
> Because drivers/i2c is only for I2C controllers and this is not a
> controller. Other address translators also reside in their respective
> subsystem, e.g. media for GMSL (de-)serializers. I don't know this chip,
> maybe it has no "respective" subsystem and, thus, misc?

That is correct, this chip acts both as an I2C address translator and as a 
GPIO controller with LED control and prefetch capabilities. It's meant to 
aggregate control signals from multiple SFP cages (or other similar port 
types), which have both I2C and low-speed signals.

Moreover, the chip can be configured to use an SPI master interface instead of 
an I2C one, although this isn't supported in this driver.

Considering all of this, I didn't think that either the I2C subsystem or the 
GPIO subsystem were a good fit for this component, which is why I chose the 
misc subsystem.

Best Regards,

-- 
Romain Gantois, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

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