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 devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
