--- a/libpam-sys/README.md	Thu Jun 26 22:42:32 2025 -0400
+++ b/libpam-sys/README.md	Sat Jun 28 00:34:45 2025 -0400
@@ -2,17 +2,17 @@
 
 This crate provides low-level access to PAM.
 
-## Options
+## Configuration
 
-With no features at all enabled, only the functions specified by the [X/SSO PAM specification][xsso] are available.
+By default, this crate guesses your system's PAM implementation based upon your OS.
 
-- `extras` (enabled by default): Common extensions to PAM, shared by both OpenPAM and Linux-PAM.
-  This includes, most notably, `pam_get_authtok`.
-  *Illumos does not provide this.*
-- `illumos-ext`: Extensions provided only by Illumos.
-- `linux-pam-ext`: Extensions provided only by Linux-PAM.
-- `openpam-ext`: Extensions provided by OpenPAM.
-- `use-system-headers`: Source constants from your PAM system headers.
+- Linux: `LinuxPam`
+- BSDs, including Mac OS: `OpenPam`
+- Illumos/Solaris: `Illumos`
+- Unknown: `OpenPamMinimal`
+
+Each implementation exports all the functionality available in its respective PAM library.
+`OpenPamMinimal` is a subset that includes only the functions available in the spec, and the constants shared in common between OpenPAM and Illumos' implementation. 
 
 ## References