Add support for reading out the VPD lock bits via MGS #1633
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Fixes #1604 |
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| // in the array which is also going to be less than `u8` | ||
| let idx = match u8::try_from(i) { | ||
| Ok(v) => v, | ||
| Err(_) => unreachable!(), |
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Nit: this feels like it should be a panic! instead, because it's not immediately obvious that it's unreachable – it's not obvious that buf.len() <= u8::MAX, since it's caller-controlled, and cnt is a usize.
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We're taking at most cnt items per take (https://doc.rust-lang.org/stable/std/iter/trait.Iterator.html#method.take) and cnt is bounded by the total number of vpd devices. If cnt was actually larger than u8 we wouldn't be able to access anything because the other APIs would reject the index. Actually hitting unreachable would indicate a system configuration error we would most likely hit elsewhere. I can change it to a panic out of an abundance of caution but given our work on reducing panic sizes it seemed reasonable to mark it as unreachable. I can try and make the comment even more explicit.
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One other way to make it clear would be changing num_vpd_devices to return a u8.
(Also, is panic! more expensive than unreachable!?)
| Ok(v) => v.into(), | ||
| Err(e) => { | ||
| return Err(SpError::Vpd(match e { | ||
| VpdError::InvalidDevice => { |
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Should we implement From<VpdError> for GatewayVpdError?
(It would have to go in vpd-api, so maybe that's too much plumbing)
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I thought about it but it seemed like overkill given the limited scope of this.
Some targets like the gimletlet have a control-plane-agent but no VPD support, hence the creation of the vpd feature. This does introduce some runtime overhead but the expectation is that this feature is not performance critical.
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