Re: [PATCH v3 02/11] media: ov772x: allow i2c controllers without I2C_FUNC_PROTOCOL_MANGLING

[Wolfram Sang <wsa@the-dreams.de>]

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> SCCB helpers would work too. It would be easy to just move the functions 
> defined in this patch to helpers and be done with it. However, there are I2C 
> adapters that have native SCCB support, so to take advantage of that feature 

Ah, didn't notice that so far. Can't find it in drivers/i2c/busses.
Where are those?

> we need to forward native SCCB calls all the way down the stack in that case. 

And how is it done currently?

> That's why I thought an implementation in the I2C subsystem would be better. 
> Furthermore, as SCCB is really a slightly mangled version of I2C, I think the 
> I2C subsystem would be a natural location for the implementation. It shouldn't 

Can be argued. But it can also be argues that it sits on top of I2C and
doesn't need to live in i2c-folders itself (like PMBus). The
implementation given in this patch looks a bit like the latter. However,
this is not the main question currently.

> be too much work, it's just a matter of deciding what the call stacks should 
> be for the native vs. emulated cases.

I don't like it. We shouldn't use SMBus calls for SCCB because SMBus
will very likely never support it. Or do you know of such a case? I
think I really want sccb helpers. So, people immediately see that SCCB
is used and not SMBus or I2C. And there, we can handle native support
vs. I2C-SCCB-emulation. And maybe SMBus-SCCB emulation but I doubt we
will ever need it.


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