On Tuesday 10 June 2014 16:36:04 Maxime Ripard wrote:
> On Tue, Jun 10, 2014 at 03:54:56PM +0200, Arnd Bergmann wrote:
> > On Tuesday 10 June 2014 15:47:16 Boris BREZILLON wrote:
> > >
> > > +config I2C_SUN6I_P2WI
> > > + tristate "Allwinner sun6i internal P2WI controller"
> > > + depends on ARCH_SUNXI
> > > + help
> > > + If you say yes to this option, support will be included for the
> > > + P2WI (Push/Pull 2 Wire Interface) controller embedded in some
> > > sunxi
> > > + SOCs.
> > > + The P2WI looks like an SMBus controller (which supports only
> > > byte
> > > + accesses), except that it only supports one slave device.
> > > + This interface is used to connect to specific PMIC devices
> > > (like the
> > > + AXP221).
> > > +
> >
> > Sorry for the stupid question, but why is this an i2c driver if the
> > hardware protocol is completely different?
>
> It's not completely different. It deviates, but still looks very
> similar to i2c, and to be precise, SMBus.
>
> You'll have the full discussion that led to do this in i2c here:
> http://www.spinics.net/lists/linux-i2c/msg15066.html
>
> Also, one significant thing to take into account is that the
> communication with a device starts as I2C, only to switch to this
> protocol after some initialization sequence.
Ok, sounds good.
> > I understand that a lot of devices can be driven using either spi or
> > i2c, and we have two sets of {directories,maintainers,bus_types,...}
> > for them. Your description sounds like this is a separate option
> > that isn't any closer to i2c than it is to spi.
>
> That's not true. It's *much* closer from I2C than it is from SPI.
Ok.
> > Would it perhaps be better to expose it only as a regmap rather than
> > an i2c host?
>
> That could be a solution, but is it a common practice to define a bus
> adapter driver in a regmap driver?
No, not yet.
Maybe Boris can just put an explanation into the changeset description
of the driver so other people are able to find it more easily.
Arnd
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
