Re: [PATCH v4 0/8] i2c-atr and FPDLink

Vaittinen, Matti
2022-11-07T12:12:41Z

On 11/7/22 13:48, Luca Ceresoli wrote:
> Hi Tomi, All,
>
> On Tue, 1 Nov 2022 15:20:24 +0200
> Tomi Valkeinen <tomi.valkeinen@ideasonboard.com> wrote:
>>
>> 2)
>> If I suggested adding an i2c-bus fwnode parameter to
>> i2c_mux_add_adapter(), and the i2c-bus might be under some other device,
>> I think the reception could be quite negative (and I would agree). For
>> this reason I'm not very happy with the i2c-atr and using it with
>> FPDLink.
>>
>> In fact, I'm thinking that it might be better to just drop the i2c-atr
>> driver, and add the support directly to the FPDlink drivers. But that
>> could mean possibly duplicating the same code for other deser/ser
>> architectures, so I have kept the i2c-atr driver for now.
>
> Indeed I think the ROHM serdes chips do have an address translation
> feature that works pretty much like the TI ones, and the ATR should be
> cleanly reusable across the two brands. The ATR code might be
> simplified to just provide helpers for common code maybe, but I'd
> rather avoid code duplication.

I tend to agree with Luca on keeping the I2C-atr a re-usable generic
code. The reason why I did not (yet) bring this (or other concerns) up
is that currently I don't have a permission to upstream my work for ROHM
SerDes Linux drivers :( I still do discuss the decision but to be
honest, I believe the chances to get my drivers upstream are getting
slim. Hence I did not see it reasonable to try pushing Tomi's / Luca's
work to any direction.

Yet, after that being said - these SerDes devices which can combine I2C
buses from multiple remote devices to one local I2C controller do bring
a real need for a solution like the address translation. Thus, I would
not be surprized if we saw new devices with this kind of feature.
Potentially also from other vendors. So, regardless what happens with
ROHM SERDESes - I (too) think we should keep the ATR as independently
reusable component.

Yours,
-- Matti Vaittinen

--
Matti Vaittinen
Linux kernel developer at ROHM Semiconductors
Oulu Finland

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