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 is based on earlier work by Daniel Baluta <daniel.baluta@xxxxxxxxx>: > https://www.spinics.net/lists/linux-iio/msg23573.html > > Changes since that version: > * Nest the adapter in inv_mpu6050_state instead of making it static > * Explicitly forward of_node "i2c-aux-master" to allow describing aux devices > via devicetree. > > For bypass/mux mode devicetree works automatically. The forwarding is based on > the "chan_id" parameter to i2c_add_mux_adapter and is implemented here: > > http://lxr.free-electrons.com/source/drivers/i2c/i2c-mux.c#L158 With any luck [1], this reference will be stale when 4.6 is released. It should be qulified with a version, something like .../i2c-mux.c?v=4.5#L158 > Perhaps it might be better for devices handled via master mode to be described > via i2c@1? This would work by scanning the mpu node's children for something > with reg == 1. The 0 in i2c@0 (which is used by the mux mode) is the index of the mux slave meaning that i2c@1 would be a second mux slave on the same mux, but this is not a real mux as such, it is a gate which is piggybacking on the i2c mux infra. So, this "mux" can't have a second slave which is why only 0 is valid. Tl;dr i2c@1 is definitely wrong for something that is not related to i2c@0. > Or maybe the two busses should be called i2c-aux-master and i2c-aux-mux? Not > sure how to deal with that on the mux side. Changing i2c to i2c-aux-mux would break existing device trees, that seems like a bad thing, no? > It is not clear how to properly handle this and suggestions are welcome. The > way it currently works with this patch is documented immediately below. I think the naming could be i2c-master0, i2c-master1 etc if it, with future work, would be possible to add more than one master (you talked about 5 i2c slaves..). Cheers, Peter [1] https://lkml.org/lkml/2016/4/20/467 -- To unsubscribe from this list: send the line "unsubscribe linux-iio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
