On 04/27/2016 11:39 AM, Peter Rosin wrote: > On 2016-04-23 23:32, Jonathan Cameron wrote: >> On 20/04/16 18:17, Crestez Dan Leonard wrote: >>> The MPU has an auxiliary I2C bus for connecting external >>> sensors. This bus has two operating modes: >>> * pass-through, which connects the primary and auxiliary busses >>> together. This is already supported via an i2c mux. >>> * I2C master mode, where the mpu60x0 acts as a master to any external >>> connected sensors. This is implemented by this patch. >>> >>> This I2C master mode also works when the MPU itself is connected via >>> SPI. >>> >>> I2C master supports up to 5 slaves. Slaves 0-3 have a common operating >>> mode while slave 4 is different. This patch implements an i2c adapter >>> using slave 4 because it has a cleaner interface and it has an >>> interrupt that signals when data from slave to master arrived. >>> >>> Signed-off-by: Crestez Dan Leonard <leonard.crestez@xxxxxxxxx> >> This one needs acks from: >> >> Device tree maintainer (odd binding ;) >> Peter Rosin (odd binding interacting with the mux support) >> Wolfram (it has a whole i2c master driver in here). >> >> (just thought I'd list these for the avoidance of doubt). > > I spot some overlap with the questions in "[RFC] i2c: device-tree: > Handling child nodes which are not i2c devices" > http://marc.info/?l=linux-i2c&m=146073452819116&w=2 > > And I think I agree with Stephen Warren that an intermediate placeholder > node would make sense. I.e. > > mpu6050@68 { > compatible = "..."; > reg = <0x68>; > ... > i2c-aux-mux { > i2c@0 { > #address-cells = <1>; > #size-cells = <0>; > reg = <0>; > > foo@44 { > compatible = "bar"; > reg = <0x44>; > ... > } > } > } > } > > Or > > mpu6050@68 { > compatible = "..."; > reg = <0x68>; > ... > i2c-aux-master { > #address-cells = <1>; > #size-cells = <0>; > > gazonk@44 { > compatible = "baz"; > reg = <0x44>; > ... > } > } > } > > depending on if you want an aux-mux or an aux-master. > > But I don't know if that intermediate i2c-aux-mux node causes any > problems? It's not clear how that would be implemented. It seems to me that right now i2c_add_mux_adapter assumes that the parent device is a dedicated mux device and all it's children are mux branches. Would this require introducing a new "struct device" for the i2c-aux-master node? It might make sense to make the automatic processing of the parents node's of_node optional and let the caller assign the of_node describing the attached devices. I think the most natural solution would be to require child nodes named i2c-aux-mux and i2c-aux-master to describe aux devices. For backwards compatibility it would be easiest to go with i2c@0/i2c@1 (identified by reg=0/1). But I don't know much about devicetree and I'd rather accept an external suggestion. Regards, Leonard -- 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
