rust-embedded/cortex-m

SCB::vect_active() should be 9 bits

Dirbaio opened this issue · 2 comments

Dirbaio commented

Currently vect_active() returns the irq number as a u8, but the SCB.ICSR.VECTACTIVE field is 9 (or more?) bits. This means that the interrupt numbers will wrap on chips with a lot of interrupts.

adamgreig commented

Yep, 9 bits. On cortex-m4 and -m7 the maximum number of interrupts is 240, which I expect is where this bug originally came from, but on -m33 it's allowed to be up to 480, which would definitely cause issues. This is basically what motivated removing bare_metal::Nr in favour of traits per architecture platform, and cortex_m::InterruptNumber being a u16... unfortunately this got missed, and since it's a breaking change it will have to wait for 0.8 I guess.

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jamesmunns commented

Could we add a new method that takes a U16 without removing the u8 one? That way we can support new targets, and just switch over the U16 one to be an alias for the future 8->16 upgraded method?