On Fri, Jun 17, 2016 at 05:30:54PM +0100, Mark Rutland wrote: > On Fri, Jun 17, 2016 at 01:03:41PM +0100, Jon Hunter wrote: > > The I2C driver core for boards using device-tree assumes any subnode of > > an I2C adapter in the device-tree blob as being a I2C slave device. > > Although this makes complete sense, some I2C adapters may have subnodes > > which are not I2C slaves but subnodes presenting other features. For > > example some Tegra devices have an I2C interface which may share its > > pins with other devices and to share these pins subnodes for > > representing these pins so they have be shared via the pinctrl framework > > are needed. > > > > To allow I2C adapters to have non-I2C specific subnodes in device-tree > > that are not parsed by the I2C driver core by adding support for a > > 'i2c-bus' subnode where I2C slaves can be placed. If the 'i2c-bus' > > subnode is present then all I2C slaves must be placed under this subnode. > > > > Signed-off-by: Jon Hunter <jonathanh@xxxxxxxxxx> > > --- > > Documentation/devicetree/bindings/i2c/i2c.txt | 8 ++++++++ > > 1 file changed, 8 insertions(+) > > > > diff --git a/Documentation/devicetree/bindings/i2c/i2c.txt b/Documentation/devicetree/bindings/i2c/i2c.txt > > index f31b2ad1552b..ed56b08c7e6e 100644 > > --- a/Documentation/devicetree/bindings/i2c/i2c.txt > > +++ b/Documentation/devicetree/bindings/i2c/i2c.txt > > @@ -32,6 +32,14 @@ wants to support one of the below features, it should adapt the bindings below. > > - clock-frequency > > frequency of bus clock in Hz. > > > > +- i2c-bus > > + For I2C adapters that have child nodes that are a mixture of both I2C > > + devices and non-I2C devices (such as a pin controller), the 'i2c-bus' > > + subnode can be used for populating I2C devices to prevent the I2C core > > + from attempting to add any non-i2c nodes as I2C devices. If 'i2c-bus' > > + subnode is present then all I2C slaves must be added under this > > + subnode. > > The general idea seems sound. > > It would be good if we could remove the mention of the I2C core, > something like: > > - i2c-bus > For I2C adapters that have child nodes that are a mixture of both I2C > devices and non-I2C devices (such as a pin controller), the 'i2c-bus' > subnode can be used for populating I2C devices. If an 'i2c-bus' > subnode is present, only subnodes of this will be considered as > I2C slaves. > > How are #address-cells and #size-cells handled in this case? I assume > that they should live under the i2c-bus subnode, which should be called > out. Good catch. Yes, I think the i2c-bus subnode would be the right place for #address-cells and #size-cells. Thierry
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