[v13,2/2] usb: typec: ucsi: add support for Cypress CCGx

[Heikki Krogerus <heikki.krogerus@linux.intel.com>]

Hi Peter,

> > I still didn't understand why can't this just be taken care of in your
> > I2C host driver? Why can't you just read 4 bytes at a time in your
> > master_xfer hook until you have received as much as the message is
> > asking, and only after that return?
> 
> The I2C host hardware *cannot* read more than 4 bytes in any one xfer
> according to the HW designers. Seriously broken crap, that piece of
> hardware... (If that assertion from the HW designers is indeed true?
> I suspect that it can be made to work, but the docs are closed and I
> don't have HW to experiment with, so it remains a suspicion...)
> 
> And the I2C host driver *cannot* be expected to know exactly how any
> one client device needs to split xfers into many when the 4 byte limit
> is getting in the way, and neither can the I2C core. Because I bet
> there are devices where it's not even possible to split xfers while
> keeping semantics equivalent...
> 
> So, every client driver will need to adjust to this quirk if they are
> to operate with this worthless I2C host (or others with similar
> limitations, if there are any?). Fortunately, most client drivers don't
> read in bulk. Unfortunately, many do...

OK, thanks for the explanation.

I think I'm repeating these questions. You guys already went through
this, so sorry for the noise.


Thanks,