On Tue, Nov 26, 2024 at 08:44:19AM -0600, Rob Herring wrote: > > > > > The DT type and name fields are pretty much legacy, so I don't think the > > > > > rust bindings need to worry about them until someone converts Sparc and > > > > > PowerMac drivers to rust (i.e. never). > > > > > > > > > > I would guess the PCI cases might be questionable, too. Like DT, drivers > > > > > may be accessing the table fields, but that's not best practice. All the > > > > > match fields are stored in pci_dev, so why get them from the match > > > > > table? > > > > > > > > Fair question, I'd like to forward it to Greg. IIRC, he explicitly requested to > > > > make the corresponding struct pci_device_id available in probe() at Kangrejos. > > Making it available is not necessarily the same thing as passing it in > via probe. IIRC, that was exactly the request. > I agree it may need to be available in probe(), but that > can be an explicit call to get it. Sure, I did exactly that for the platform abstraction, because there we may probe through different ID tables. A `struct pci_driver`'s probe function has the following signature [1] though: `int (*probe)(struct pci_dev *dev, const struct pci_device_id *id)` [1] https://elixir.bootlin.com/linux/v6.12/source/include/linux/pci.h#L950 > > > > Which table gets passed in though? Is the IdInfo parameter generic and > > > can be platform_device_id, of_device_id or acpi_device_id? Not sure if > > > that's possible in rust or not. > > > > Not sure I can follow you here. > > > > The `IdInfo` parameter is of a type given by the driver for driver specific data > > for a certain ID table entry. > > > > It's analogue to resolving `pci_device_id::driver_data` in C. > > As I said below, the PCI case is simpler than for platform devices. > Platform devices have 3 possible match tables. The *_device_id type we > end up with is determined at runtime (because matching is done at > runtime), so IdInfo could be any of those 3 types. `IdInfo` is *not* any of the three *_device_id types. It's the type of the drivers private data associated with an entry of any of the three ID tables. It is true that a driver, which registers multiple out of those three tables is currently forced to have the same private data type for all of them. I don't think this is a concern, is it? If so, it's easily resolvable by just adding two more associated types, e.g. `PlatformIdInfo`, `DtIdInfo` and `AcpiIdInfo`. In this case we would indeed need accessor functions like `dt_match_data`, `platform_match_data`, `acpi_match_data`, since we don't know the type at compile time anymore. I don't think that's necessary though. > Is the exact type > opaque to probe() and will that magically work in rust? Or do we need > to pass in the 'driver_data' ptr (or reference) itself? The matched > driver data is generally all the driver needs or cares about. We can > probably assume that it is the same type no matter which match table > is used whether it is platform_device_id::driver_data, > of_device_id::data, or acpi_device_id::driver_data. Nothing in the C > API guarantees that, but that's just best practice. Best practice in C > looks like this: > > my_probe() > { > struct my_driver_data *data = device_get_match_data(); > ... > } > > device_get_match_data() is just a wrapper to handle the 3 possible match tables. > > The decision for rust is whether we pass in "data" to probe or have an > explicit call. There is a need to get to the *_device_id entry, but > that's the exception. I would go as far as saying we may never need > that in rust drivers. > > Rob > > > > PCI is the exception, not the rule here, in that it only matches with > > > pci_device_id. At least I think that is the case currently, but it is > > > entirely possible we may want to do ACPI/DT matching like every other > > > bus. There are cases where PCI devices are described in DT. > > > > > > Rob > > > >
