On 2016-04-28 12:39, Crestez Dan Leonard wrote: > 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.cres...@intel.com> >>> 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. > I was thinking that with the new i2c_mux_core in place, it should be pretty simple to add a hook to point to another node and only use dev->of_node as a default value for where to look for the mux child adapters?
Cheers, Peter
