Re: [PATCH RFC 0/4] Adding DT functionality to w1 busses

[Daniel Mack]

On Tuesday, June 26, 2018 11:39 PM, Rob Herring wrote:
> On Tue, Jun 19, 2018 at 3:27 PM, Daniel Mack <daniel@xxxxxxxxxx> wrote:
> > In order to fully move battery-supplied devices over to devicetree, the
> > onewire subsystem must get some updates.
> >
> > Currently, the w1 bus system works like this. Device families, such as
> > battery controllers etc, are registered to the w1 core. Once a master
> > device is probed, it starts scanning the bus. Slave devices that are
> > revealed through this scan and that match previously registered
> > families are then registered, and their .add_slave() callback is
> > invoked.
> >
> > Some devices, such as the ds2760, use that callback to call
> > platform_device_alloc() at runtime with a fixed device name to
> > instanciate their only user. That user does the actual work, while the
> > slave device merely functions as an I/O proxy. In the user
> > implementation, the w1 slave device is accessible through
> > dev->parent.
>
> Looks to me like you are letting the driver structure define the DT
> structure. This detail is all irrelevant to DT.
>
> > Now, for devicetree environments, this has to change a bit. First, slave
> > devices need to have a matching table so they can be listed as sub-nodes
> > of their master bus controller. Second, the core needs to match the
> > entries in these tables against the sub-nodes of the master node.
> > These two are trivial to do.
> >
> > The next question is how the w1 slave device and its user(s) are linked
> > together. I'm proposing a DT layout with the following example:
> >
> >          onewire {
> >                  compatible = "w1-gpio";
> >
> >                  w1_slave: slave@0 {
> >                          compatible = "maxim,w1-ds2760";
> >                  };
> >          };
> >
> >          battery-supply {
> >                  compatible = "maxim,ds2760-supply";
> >                  w1-slave = <&w1_slave>;
> >          };
>
> This should just be one node and a child of the 1-wire master.

Yeah, you're right. This also makes the patch set much simpler.

Thanks for the feedback - I'll send another round of patches.



Daniel