Hi,

On 03/11/2014 11:44 AM, Maxime Ripard wrote:
> Hi Hans,
> 
> (you should really fix your mailer, it has the bad habit of screwing
> the wrapping)

Yeah that is caused by enigmail, sorry about that it should be fixed now

> On Tue, Mar 11, 2014 at 11:16:16AM +0100, Hans de Goede wrote:
>>> There's still some subtleties I don't get yet, but the more I
>>> think about this, the more I feel like we'll have to write our own
>>> bus :(
>>
>> So on the bus things are different then with i2c, that does not mean
>> we cannot still pretend it is i2c to upper layers in the kernel.
> 
> The fact that it's not having any ACK, nor any address is kind of a
> show stopper. For all we now, we could just as much pretend it's SPI :)

According to:
https://github.com/oliv3r/u-boot-sunxi/commit/52b8454fb8951e95da76b3d9ba82461adab5ee7f

It does have a device address, and if I read your previous mail
correct, there is an ack.

>> I still believe we should try to make this some kind of pseudo i2c
>> controller and not do a new bus for this. If you look at the axp209
>> code intended for upstream then it uses a lot of i2c infra, not just
>> the bus stuff, but also things like devm_regmap_init_i2c, so if we
>> do our own bus we would need to write out own regamp glue for that
>> bus too.
> 
> Regmap isn't mandatory. At all. We can do perfectly fine without it.

True, but it is quite useful.

> 
> Plus, a lot of devices can actually be plugged onto several different
> buses, and have driver that add a small layer to access registers
> depending on which bus they're loaded from.
> 
> We could very well imagine having to use regmap for the i2c part, and
> p2wi bus calls for the A31's case.

This actually sounds like something which using a regmap would make
easier to do.


> 
>> And if we try and fail we can always define our own bus for this
>> later.
> 
> You can still ask the i2c maintainer, but I'm afraid I know his
> answer.

As said before I think we first need to learn more about how this
bus works before we can make a call one way or the other.

Regards,

Hans

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