Hi Geert, On Wed, May 31, 2023 at 02:51:48PM +0200, Geert Uytterhoeven wrote: > On Wed, May 31, 2023 at 10:59 AM Laurent Pinchart wrote: > > On Mon, May 29, 2023 at 09:00:43AM +0000, Biju Das wrote: > > > > Subject: Re: [PATCH v5 01/11] i2c: Enhance i2c_new_ancillary_device API > > > > And why do you need this ? > > > > > > As per Krzysztof [2], > > > > > > The DT schema allows multiple addresses for children. But we lack > > > implementation of parent child relationship, As parent owns the resources. > > > Child device needs to parse parent node to get some resource > > > like clocks. > > > > > > [2] https://lore.kernel.org/linux-renesas-soc/TYCPR01MB5933BFFD4EB556F5FB4EA82186729@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/ > > > > The I2C ancillary clients are not meant to be handled by separate > > drivers. You're supposed to have one device node in DT, which causes the > > I2C core to instantiate a main i2c_client, and bind it to one driver. > > That driver then uses i2c_new_ancillary_device() to create other > > i2c_client instances for the secondary I2C addresses. Those i2c_client > > instances are not bound to a separate driver, so there should be no code > > that needs to look at the parent for resources. > > In Biju's particular use case, the i2c device responds to two addresses, > which is the standard i2c ancillary use case. However, what's special > is that the second instance is a derivative of an existing i2c device > with an existing Linux driver. Hence the desire to make the existing > driver match against the second instance, which requires these changes > to i2c_new_ancillary_device(). > > As some resources are shared (knowledge about the clocks), splitting > this in two distinct devices in DT (which is what Biju's initial patch > series did) would need phandles to link both nodes together. > > Do you have a better idea how to represent this? MFD ? Otherwise, I'll delegate that to Wolfram, I've spent enough time on this patch series I'm afraid :-) > Wolfram: time to chime in ;-) -- Regards, Laurent Pinchart
