Messages in this thread | | | Date | Thu, 9 Mar 2023 18:11:18 +0100 | From | Greg Kroah-Hartman <> | Subject | Re: [PATCH 5/5] rust: device: Add a stub abstraction for devices |
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On Thu, Mar 09, 2023 at 01:46:39PM -0300, Wedson Almeida Filho wrote: > On Thu, 9 Mar 2023 at 08:24, Greg Kroah-Hartman > <gregkh@linuxfoundation.org> wrote: > > > > > + // owns a reference. This is satisfied by the call to `get_device` above. > > > > > + Self { ptr } > > > > > + } > > > > > + > > > > > + /// Creates a new device instance from an existing [`RawDevice`] instance. > > > > > + pub fn from_dev(dev: &dyn RawDevice) -> Self { > > > > > > > > I am a rust newbie, but I don't understand this "RawDevice" here at all. > > > > > > Different buses will have their own Rust "Device" type, for example, > > > pci::Device, amba::Device, platform::Device that wrap their C > > > counterparts pci_dev, amba_device, platform_device. > > > > > > "RawDevice" is a trait for functionality that is common to all > > > devices. It exposes the "struct device" of each bus/subsystem so that > > > functions that work on any "struct device", for example, `clk_get`, > > > `pr_info`. will automatically work on all subsystems. > > > > Why is this being called "Raw" then? Why not just "Device" to follow > > along with the naming scheme that the kernel already uses? > > Because it gives us access to underlying raw `struct device` pointer, > in Rust raw pointers are those unsafe `*mut T` or `*const T`. I'm not > married to the name though, we should probably look for a better one > if this one is confusing. > > Just "Device" is already taken. It's a ref-counted `struct device` (it > calls get_device/put_device in the right places automatically, > guarantees no dandling pointers); it is meant to be used by code that > needs to hold on to devices when they don't care about the bus. (It in > fact implements `RawDevice`.)
I don't understand, why do you need both of these? Why can't one just do? Why would you need one without the other? I would think that "Device" and "RawDevice" here would be the same thing, that is a way to refer to a "larger" underlying struct device memory chunk in a way that can be passed around without knowing, or caring, what the "real" device type is.
> How about `IsDevice`?
That sounds like a question, and would return a boolean, not a structure :)
> Then, for example, the platform bus would implement `IsDevice` for > `plaform::Device`.
I don't really understand that, sorry.
thanks,
greg k-h
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