Mapping a Card's Register Window
A card announces where its control registers should appear in the machine's address space, but that region is not usable until the driver asks the kernel to reserve it and map it for access. The Rust method does all of it at once, returning a device-managed mapping whose size you state up front, so the compiler knows how large the window is and can check offsets against it. Because the mapping is device managed, it is torn down at unbind without any code from you. In C, a mapping taken without the matching request is how two drivers end up poking the same registers.
Questions this Concept answers
- Why do you state the window size up front when mapping a BAR in Rust?
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A card announces where its control registers should appear in the machine's address space, but that region is not usable until the driver asks the kernel to reserve it and map it for access. The Rust method does all of it at once, returning a device-managed mapping whose size you state up front, so the compiler knows how large the window is and can check offsets against it. Because the mapping is device managed, it is torn down at unbind without any code from you. In C, a mapping taken without the matching request is how two drivers end up poking the same registers.
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