On Wed, 6 Jan 2021 14:59:31 +0000, Mark Brown wrote: > On Tue, Jan 05, 2021 at 05:55:29PM +0100, Krzysztof Kozlowski wrote: > > On Mon, Jan 04, 2021 at 09:24:49PM +0000, Mark Brown wrote: > > > > I'm not sure I follow, sorry? Either the core driver can parse the > > > bindings enough to know what children it has or (probably better) it can > > > instantiate the children unconditionally and then the function drivers > > > can figure out if they need to do anything. > > > Currently the MFD parent/core driver will instantiate children > > unconditionally. It would have to be adapted. With proposed bindings - > > nothing to change. MFD core already does the thing. > > We're not talking massive amounts of code here, but we are talking ABI > for a DT update. > > > The point is that function drivers should not be even bound, should not > > start to probe. Otherwise if they probe and fail, they will pollute the > > dmesg/probe log with failure. With the failure coming from looking for > > missing of_node or any other condition from parent/core driver. > > There will only be an error message if one is printed, if we can do a > definitive -ENODEV there should be no need to print an error. > > > > > Another point, is that this reflects the real hardware. The same as we > > > > model entire SoC as multiple children of soc node (with their own > > > > properties), here we represent smaller chip which also has > > > > sub-components. > > > > Components we're calling things like "extcon"... > > > I am rather thinking about charger, but yes, extcon as well. Either you > > have USB socket (and want to use associated logic) or not. > > Right, I'm just saying we don't need to add new device nodes reflecting > implementation details into the DT to do that. I'm not sure I can contribute that much to this discussion (this is my first proper kernel patch, also I don't really understand the argument). FWIW I looked at other MFD devices while implementing this like max77836, max77693, max77650, max77843 (just to name a few). Assigning of_node to sub-devices using sub-nodes with compatible strings seemed to be a common pattern for MFD devices. Muic needs a node to be used with extcon_get_edev_by_phandle(). Charger needs a node to reference a regulator.
