stm32xx-sys: fix typo in EXTI pin configuration #1717
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In the Giant Scary Nested Match we had to write to be able to address the EXTI register array as an array through the PAC, I typo'd the number base being used to select the field within the register, by reusing 2 from the line above. This is the _base 2 logarithm_ of the number we actually wanted, 4, because the operations are shift and mod, respectively. Wheeee Anyway, this fixes the situation where EXTI configuration of any pin p such that p % 4 = 2 or 3 on any port other than A mysteriously senses a different pin in port A instead.
hawkw
approved these changes
Apr 3, 2024
| @@ -398,7 +398,7 @@ fn main() -> ! { | |||
| // Process entries that are filled in... | |||
| if let &Some(ExtiDispatch { port, .. }) = entry { | |||
| let register = i >> 2; | |||
| let slot = i % 2; | |||
| let slot = i & 0b11; | |||
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i waffled on whether & 0b11 or % 4 expresses intent more clearly --- i'm now mildly leaning towards % 4 based on the observation that there are 4 bitfields per register. but, it doesn't actually matter.
I do think that it might be nice if the register and slot calculation was below the comment describing what we're doing --- it's possible i didn't notice this in the review because i was too top-to-bottom in my reading habits, and didn't think to go back and look at the calculations after reading the comment explaining what they were doing. but, whether or not that would have prevented this is probably not really worth thinking too hard about 🤷♀️
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In the Giant Scary Nested Match we had to write to be able to address the EXTI register array as an array through the PAC, I typo'd the number base being used to select the field within the register, by reusing 2 from the line above. This is the base 2 logarithm of the number we actually wanted, 4, because the operations are shift and mod, respectively.
Wheeee
Anyway, this fixes the situation where EXTI configuration of any pin p such that p % 4 = 2 or 3 on any port other than A mysteriously senses a different pin in port A instead.