--- a/libpam-sys/libpam-sys-impls/README.md	Thu Jul 31 15:42:12 2025 -0400
+++ b/libpam-sys/libpam-sys-impls/README.md	Sat Aug 02 18:47:46 2025 -0400
@@ -1,66 +1,12 @@
 # `libpam-sys-impls`: LibPAM library detection
 
 This crate detects what implementation of LibPAM should be used, as part of the build script, and exports that information to downstream crates.
+It can also be used at runtime, but is primarily intended for build scripts.
 
-This is mostly a backend crate for [libpam-sys](https://crates.io/crates/libpam-sys/).
+Its main use is as a backend for [libpam-sys](https://crates.io/crates/libpam-sys/).
 That crate re-exports pretty much everything we provide.
 In most cases, you can just use that instead of depending upon this directly.
 
-## Usage
-
-Different PAM implementations have different constants and some different behaviors.
-If you need to change your library's behavior based on PAM implementation, there are a few ways to do so.
-
-### Constants
-
-You can match on the current PAM implementation at runtime.
-All known PAM implementations are in the `PamImpl` enumeration, and `PamImpl::CURRENT` is set to the current implementation.
-This is present as a string literal macro in `pam_impl_name!`.
-
-### Conditional compilation
-
-This package provides custom `#[cfg]`s to compile based on the current PAM implementation.
-
-First, **enable custom `#[cfg]`s in your build.rs**:
-
-```rust
-// build.rs
-use libpam_sys_impls::pam_impl;
-
-fn main() {
-    pam_impl::enable_pam_impl_cfg();
-    
-    // everything else you do at build time
-}
-```
-
-This will then allow you to use the `pam_impl` configuration variable at compile time:
-
-```rust
-#[cfg(pam_impl = "LinuxPam")]
-fn handle_pam() {
-    // do things in a Linux-PAM specific way
-}
-
-#[cfg(not(pam_impl = "LinuxPam"))]
-fn handle_pam() {
-    // do things in another, more different way
-}
-```
-
-## Configuration
-
-Known implementations of PAM are listed in the `PamImpl` enum, and your currently installed implementation is automatically detected.
-
-If you need to configure this, you can override it **at build time** with the `LIBPAMSYS_IMPL` environment variable:
-
-- Unset or empty (the default): Use the version of PAM most commonly found on the target OS.
-  If we don't know what kind of PAM is usually installed on this OS, we fall back to `__installed__`.
-- `__installed__`: Looks at the PAM library installed on the current machine.
-  If none is recognized, falls back to `XSso`.
-- The name of a `PamImpl` entry: The named PAM implementation.
-  For instance, `LIBPAMSYS_IMPL=OpenPam cargo build` will build this library for OpenPAM.
-
 ## MSRV
 
 This library supports **Rust 1.75**, as the version currently (July 2025) available in Debian Trixie and Ubuntu 24.04 LTS.
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