On 04/17/2014 12:36 PM, Doug Anderson wrote: > On ARM Chromebooks we have a few devices that are accessed by both the > AP (the main "Application Processor") and the EC (the Embedded > Controller). These are: > * The battery (sbs-battery). > * The power management unit tps65090. ... > On the Samsung ARM Chromebook 2 the scheme is changed yet again, now: > * The AP/EC comms are now using SPI for faster speeds. > * The EC's i2c bus is exposed to the AP through a full i2c tunnel. ... > This driver supports the scheme used by the Samsung ARM Chromebook 2. > Future patches to this driver could add support for the battery tunnel > on the HP Chromebook 11 (and perhaps could even be used to access > tps65090 on the HP Chromebook 11 instead of using a special driver, > but I haven't researched that enough). > diff --git a/Documentation/devicetree/bindings/i2c/i2c-cros-ec-tunnel.txt b/Documentation/devicetree/bindings/i2c/i2c-cros-ec-tunnel.txt > +I2C bus that tunnels through the ChromeOS EC (cros-ec) > +====================================================== > +On some ChromeOS board designs we've got a connection to the EC (embedded > +controller) but no direct connection to some devices on the other side of > +the EC (like a battery and PMIC). To get access to those devices we need > +to tunnel our i2c commands through the EC. > + > +The node for this device should be under a cros-ec node like google,cros-ec-spi > +or google,cros-ec-i2c. > + > + > +Required properties: > +- compatible: google,cros-ec-i2c-tunnel > +- google,remote-bus: The EC bus we'd like to talk to. It's probably worth mentioning here that the node represents a single I2C bus, and hence is expected to contain child nodes representing I2C devices. Perhaps: Optional child nodes: - One node per I2C device connected to the tunnelled I2C bus. -- 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
