On Tue, 1 Aug 2017 16:12:18 +0200 Wolfram Sang <wsa@xxxxxxxxxxxxx> wrote: > > > The second way is to have a number of #ifdef and complex > > > Kconfig dependencies for the driver to only register the > > > device_driver objects for the buses that are enabled. This > > > is also doable, but everyone gets the logic wrong the first time. > > > > Hm, I understand now why you'd prefer to have a single bus. Can't we > > solve this problem with a module_i3c_i2c_driver() macro that would hide > > all this complexity from I2C/I3C drivers? > > Do you know of devices speaking both i3c and i2c as of today? I do not know of any real devices as of today (all my tests have been done with a dummy/fake I3C slaves emulated with a slave IP), but the spec clearly describe what legacy/static addresses are for and one of their use case is to connect an I3C device on an I2C bus and let it act as an I2C device. > > I think I3C/I2C is a bit different than I2C/SPI. For the latter, it > might happen that you have only this or that bus on the board, so it > makes sense to support both. But if you have I3C, you can simply attach > the I2C device onto it. I guess you would only implement I3C in the > device if you explicitly need its feature set. And then, a I2C fallback > doesn't make much sense? Or am I missing something? Unless you want your device (likely a sensor) to be compatible with both I3C and I2C so that you can target even more people. > > OK, now I know that those I3C+I2C devices will exist, even if only for > Murphy's law. However, my assumptions would be that those devices are > not common and so we could live with the core plus bus_drivers > seperation we have for SPI/I2C already (although I would love a common > regmap-based I2C/SPI abstraction). > I'm perfectly fine with the I3C / I2C framework separation. The only minor problem I had with that was the inaccuracy of the sysfs/device-model representation: we don't have one i2c and one i3c bus, we just have one i3c bus with a mix of i2c and i3c devices. Apart from that, I'm happy with the current approach.
