On Wed, Mar 28, 2018 at 3:19 AM, Boris Brezillon <boris.brezillon@xxxxxxxxxxx> wrote: > Hi Rob, > > On Mon, 26 Mar 2018 17:24:58 -0500 > Rob Herring <robh@xxxxxxxxxx> wrote: > >> > + >> > +I3C devices >> > +=========== >> > + >> > +All I3C devices are supposed to support DAA (Dynamic Address Assignment), and >> > +are thus discoverable. So, by default, I3C devices do not have to be described >> > +in the device tree. >> > +This being said, one might want to attach extra resources to these devices, >> > +and those resources may have to be described in the device tree, which in turn >> > +means we have to describe I3C devices. >> > + >> > +Another use case for describing an I3C device in the device tree is when this >> > +I3C device has a static address and we want to assign it a specific dynamic >> > +address before the DAA takes place (so that other devices on the bus can't >> >> static is I2C address and dynamic is an I3C address. That could be >> clearer throughout. > > I'll clarify that. > >> >> > +take this dynamic address). >> > + >> > +The I3C device should be names <device-type>@<static-address>,<i3c-pid>, >> >> s/static-address/static-i2c-address/ > > Okay. > >> >> > +where device-type is describing the type of device connected on the bus >> > +(gpio-controller, sensor, ...). >> > + >> > +Required properties >> > +------------------- >> > +- reg: contains 3 cells >> > + + first cell : encodes the I2C address. Should be 0 if the device does not >> > + have one (0 is not a valid I3C address). >> >> Change here to "encodes the static I2C address". >> >> 0 is not a valid I2C address? > > According to [1] it is reserved, and it's reserved in the I3C spec > anyway (see "Table 9 I3C Slave Address Restrictions" in the I3C spec). Sorry, what I meant was s/I3C/I2C/. The first cell is I2C address and 0 is not valid. >> > + >> > + + second and third cells: should encode the ProvisionalID. The second cell >> > + contains the manufacturer ID left-shifted by 1. >> > + The third cell contains ORing of the part ID >> > + left-shifted by 16, the instance ID left-shifted >> > + by 12 and the extra information. This encoding is >> > + following the PID definition provided by the I3C >> > + specification. > > One extra question for you: should I refer to the I3C_DEV(), > I3C_DEV_WITH_STATIC_ADDR() and I2C_DEV() macros in the bindings doc? > And if I do, should I use them my example? Well, I don't want to see "device@I3C_DEV(...)" for unit-addresses. You can use them for reg property, but it's somewhat pointless to use it in one place and not the other. Rob -- 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
