Ethernet merge

[hargoniX]

This PR adds stm32h7-ethernet into the HAL behind the ethernet feature flag, trying to introduce as little diff as possible in the process of doing so.

Closes: #102

[ryan-summers]

@hargoniX / @richardeoin After getting this in, I would like to hear your potential thoughts on the following:

1. Should we pull the phy support out (or provide a generic trait such that users can provide their own phy support if required)?
2. Let's clean up the pins definition - we should be able to take a Pins structure in the constructor similar to other peripherals
3. I'd really like to clean up the unsafe-ness here, but I'm not familiar as to why its originally there.

Curious to hear your thoughts here - we can break this out into an issue if necessary.

[richardeoin]

1. I agree it would be nice to pull out the PHY support. The PHY trait is there already in ethernet/mod.rs, but currently we use the feature flags to choose an implementation, rather than allowing the user to pass generic object that implements PHY. Definitely fixable.

2. Good point, I'd missed that we don't offer a way to check the pins. Definitely we should keep the same new /new_unchecked pattern.

3. I think there's always going to be some unsafe because of the DMA interaction. But we can definitely reduce it, especially in the public API. A good place to start would be ethernet_init, I don't think it actually needs to be unsafe. But I think users would need unsafe to take the DesRing from static storage?

[richardeoin]

@ryan-summers Do you want to merge this now, and then continue with those 3 points in another PR?

[ryan-summers]

Let's merge as-is and open issues for updates

…

On Wed, Aug 12, 2020, 21:55 Richard Meadows ***@***.***> wrote: @ryan-summers <https://github.com/ryan-summers> Do you want to merge this now, and then continue with those 3 points in another PR? — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#121 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ACC5O6T4R4S57OYWVUZUEA3SALXURANCNFSM4PZGEK4A> .

[richardeoin]

Ok!

bors r+

[bors]

Build succeeded:

• ci (1.43.0, stm32h743)
• ci (1.43.0, stm32h743v)
• ci (1.43.0, stm32h747cm7)
• ci (1.43.0, stm32h753)
• ci (1.43.0, stm32h753v)
• ci (stable, stm32h743)
• ci (stable, stm32h743v)
• ci (stable, stm32h747cm7)
• ci (stable, stm32h753)
• ci (stable, stm32h753v)
• Rustfmt