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.
Rob
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