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rust-embedded-community / embedded-storage

An Embedded Storage Abstraction Layer
Apache License 2.0
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Add BlockDevice trait. #59

Open qwandor opened 1 month ago

qwandor commented 1 month ago

Fixes #56.

Sympatron commented 1 month ago

Shouldn't BLOCK_SIZE be an associated constant?

qwandor commented 1 month ago

Shouldn't BLOCK_SIZE be an associated constant?

I tried that but unfortunately it doesn't work, as Rust doesn't allow associated constants to be used in the types of trait methods. We can make it a trait parameter though.

In practice the crates I've checked so far both use 512 byte blocks. virtio-drivers uses 512 byte blocks for VirtIO block devices (as required by the VirtIO specification), embedded-sdmmc uses 512 blocks for SD cards and FAT32. Implementing block devices with other block sizes is less useful, as they won't be able to be used with filesystem drivers which expect 512 byte blocks. (On the other hand filesystems which work with larger blocks can be implemented just fine against a device which has 512 byte blocks, as they can just read or write multiple blocks at once if needed.)

qwandor commented 3 weeks ago

Any further comments on this? Can it be merged?

thejpster commented 2 weeks ago

I'm fine with just adding Block in the first instance, which is a [u8; 512] and then having the BlockDevice trait not be generic over block size. The set of things that don't have 512 byte blocks (especially in an embedded context) is very small, and most of those will simply be a [u8; 4096], which we can add as a LargeBlock or Block4K.