2024-08: uefi v0.31 significant changes

Author: phip1611

content/this-month/2024-08/index.md

@@ -4,7 +4,7 @@ date = 2024-09-03
 
 [extra]
 month = "August 2024"
-editors = ["phil-opp"]
+editors = ["phil-opp", "phip1611"]
 +++
 
 Welcome to a new issue of _"This Month in Rust OSDev"_. In these posts, we give a regular overview of notable changes in the Rust operating system development ecosystem.
@@ -101,6 +101,105 @@ In this section, we give an overview of notable changes to the projects hosted u
     <<changelog, either in list or text form>>
 -->
 
+### [`uefi`](https://github.com/rust-osdev/uefi-rs)
+<span class="maintainers">Maintained by [@GabrielMajeri](https://github.com/GabrielMajeri), [@nicholasbishop](https://github.com/nicholasbishop), and [@phip1611](https://github.com/phip1611)</span>
+
+`uefi` makes it easy to develop Rust software that leverages safe, convenient,
+and performant abstractions for UEFI functionality. Recently, we released 
+version `v0.31` with some notable changes:
+
+1. We introduced a completely new API to access boot and runtime services
+2. We reorganized the MemoryMap-related types.
+3. We reorganized the repository README's and `lib.rs` files (documentation for
+   docs.rs)
+4. We talk about how the `std` implementation for UEFI targets compares to
+   `uefi` and how both can be used together.
+
+### 1. New API: Freestanding Functions API Change
+
+We are planning a massive API change and introduced a new replacement API in
+release `v0.31`. The old API co-exists and will be marked as 
+`#[deprecated]` in `0.32`. The new API will make it easier to call boot or 
+runtime services without having to pass `&BootServices` around all the time.
+
+The typical use-case of our library users is to write UEFI image with code 
+leveraging boot services and exiting them. Next, control is handed over to the
+next step, which is typically a kernel of an OS. These UEFI images typically
+are "99% code" using boot services, until they are exited.
+
+Although the old API design ensures via the type system that no boot
+services can be called after they have been exited, the test of time has proven
+that this adds unjustified complexity without bringing much real value add.
+
+Instead, with the new API, which we provide **additionally** at this point,
+one can use freestanding functions which are behind the new modules:
+
+- `uefi::system`: is a new module that provides freestanding functions for
+  accessing fields of the global system table.
+- `uefi::boot`:
+  is a new module that provides freestanding functions for boot services using
+  the global system table.
+- `uefi::runtime`: is a new module that provides freestanding functions for
+  runtime services using the global system table.
+
+The freestanding functions itself are close to the originals ones but without
+`&BootServices` or `&RuntimeServices` parameters, as you can see for example
+[here](https://github.com/rust-osdev/uefi-rs/pull/1344/files#diff-46f1e3c04d719fff471faf35c4d218430e1d664ac0a0fab9d2c15870c2d0f066).
+
+The new API design solves API inconsistencies and restrictions already existing
+so far, and makes the overall handling a lot easier. This comes with the costs
+that functions may panic, if the boot services were exited but one tries to use
+them. However, the massive API simplification justifies this.
+
+Find more and follow the progress and discussions on:
+- [the GitHub Issue](https://github.com/rust-osdev/uefi-rs/issues/893#issuecomment-2241610633).
+- [The function Migration Guide](https://github.com/rust-osdev/uefi-rs/blob/main/docs/funcs_migration.md)
+
+#### 2. Memory Map Refactoring
+
+TL;DR: What used to return `MemoryMap<'buf>` in the API, now returns
+`MemoryMapOwned`. Additionally, you can parse a chunk of memory using
+`MemoryMapRef` or `MemoryMapRefMut`.
+
+We put significant effort into refactoring our abstractions for the UEFI memory 
+map. These started in release v0.29 and were finalized in release v0.31. 
+Instead of one `MemoryMap<'buf>` type, we now have the traits `MemoryMap` and 
+`MemoryMapMut` along with the implementations `MemoryMapRef`, `MemoryMapRefMut`, 
+and `MemoryMapOwned`. It is recommended to work with the specific 
+implementations, as the main purpose for the traits is only to enforce a 
+consistent API for these three implementations. This gives users the 
+flexibility to cover all possible use cases one can have with an UEFI memory 
+map. Read more:
+- [#1175](https://github.com/rust-osdev/uefi-rs/pull/1175)
+- [#1251](https://github.com/rust-osdev/uefi-rs/pull/1251)
+- [#1240](https://github.com/rust-osdev/uefi-rs/pull/1240)
+- [#1263](https://github.com/rust-osdev/uefi-rs/pull/1263)
+
+In any case, obtaining the memory map from UEFI is hidden behind the
+public API of the crate, but we made it very easy to read/parse it in all
+possible scenarios!
+
+#### 3. & 4.: Documentation Reorganization
+
+We put notable work into our README and `lib.rs` files to improve the
+structure of our documentation. The main value-add and improvement is that we 
+clearly, directly, and precisely talk about:
+
+- What is `uefi`?
+- Which problems does it solve?
+- How can it be used?
+- How does it compare to the ecosystem, such as `std` for Rust targets?
+
+To see an example how `uefi` and `std` can be used together, please head to
+[our repository](https://github.com/rust-osdev/uefi-rs/tree/main/uefi-std-example).
+
+### Other
+
+There were also a ton of other interesting fixes, changes, and additions! 
+Check out our [Changelog](https://github.com/rust-osdev/uefi-rs/blob/main/uefi/CHANGELOG.md).
+
+We merged the following PRs this month:
+<!-- todo -->
 
 ## Other Projects
 
@@ -115,7 +214,6 @@ In this section, we describe updates to Rust OS projects that are not directly r
     ...<<your project updates>>...
 -->
 
-
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