On Mon, Jan 4, 2021 at 5:53 PM Jason Gunthorpe <jgg@xxxxxxxxxx> wrote: > > On Mon, Jan 04, 2021 at 04:51:51PM -0800, Dan Williams wrote: > > On Mon, Jan 4, 2021 at 4:14 PM Jason Gunthorpe <jgg@xxxxxxxxxx> wrote: > > > > > > On Mon, Jan 04, 2021 at 09:19:30PM +0000, Mark Brown wrote: > > > > > > > > > > > Regardless of the shortcut to make everything a struct > > > > > platform_device, I think it was a mistake to put OF devices on > > > > > platform_bus. Those should have remained on some of_bus even if they > > > > > > > > Like I keep saying the same thing applies to all non-enumerable buses - > > > > exactly the same considerations exist for all the other buses like I2C > > > > (including the ACPI naming issue you mention below), and for that matter > > > > with enumerable buses which can have firmware info. > > > > > > And most busses do already have their own bus type. ACPI, I2C, PCI, > > > etc. It is just a few that have been squished into platform, notably > > > OF. > > > > > > > I'll note that ACPI is an outlier that places devices on 2 buses, > > where new acpi_driver instances are discouraged [1] in favor of > > platform_drivers. ACPI scan handlers are awkwardly integrated into the > > Linux device model. > > > > So while I agree with sentiment that an "ACPI bus" should > > theoretically stand on its own there is legacy to unwind. > > > > I only bring that up to keep the focus on how to organize drivers > > going forward, because trying to map some of these arguments backwards > > runs into difficulties. > > > > [1]: http://lore.kernel.org/r/CAJZ5v0j_ReK3AGDdw7fLvmw_7knECCg2U_huKgJzQeLCy8smug@xxxxxxxxxxxxxx > > Well, this is the exact kind of thing I think we are talking about > here.. > > > > It should be split up based on the unique naming scheme and any bus > > > specific API elements - like raw access to ACPI or OF data or what > > > have you for other FW bus types. > > > > I agree that the pendulum may have swung too far towards "reuse > > existing bus_type", and auxiliary-bus unwinds some of that, but does > > the bus_type really want to be an indirection for driver apis outside > > of bus-specific operations? > > If the bus is the "enumeration entity" and we define that things like > name, resources, gpio's, regulators, etc are a generic part of what is > enumerated, then it makes sense that the bus would have methods > to handle those things too. > > In other words, the only way to learn what GPIO 'resource' is to ask > the enumeration mechnism that is providing the bus. If the enumeration > and bus are 1:1 then you can use a function pointer on the bus type > instead of open coding a dispatch based on an indirect indication. > I get that, but I'm fearing a gigantic bus_ops structure that has narrow helpers like ->gpio_count() that mean nothing to the many other clients of the bus. Maybe I'm overestimating the pressure there will be to widen the ops structure at the bus level.
