fix(rsdp): fix rsdp revision and rsdp checksum to fit linux kernel impl

src/lib.rs

@@ -112,15 +112,12 @@ where
         }
 
         let rsdp_revision = rsdp_mapping.revision();
-        let rsdt_address = if rsdp_revision == 0 {
-            // We're running on ACPI Version 1.0. We should use the 32-bit RSDT address.
-            rsdp_mapping.rsdt_address() as usize
-        } else {
-            /*
-             * We're running on ACPI Version 2.0+. We should use the 64-bit XSDT address, truncated
-             * to 32 bits on x86.
-             */
+        // Use XSDT only when revision > 1, following Linux (tbutils.c).
+        // revision == 0 and revision == 1 both use the 32-bit RSDT address.
+        let rsdt_address = if rsdp_revision > 1 {
             rsdp_mapping.xsdt_address() as usize
+        } else {
+            rsdp_mapping.rsdt_address() as usize
         };
 
         unsafe { Self::from_rsdt(handler, rsdp_revision, rsdt_address) }

src/rsdp.rs

@@ -3,6 +3,8 @@ use core::{mem, ops::Range, slice, str};
 
 /// The size in bytes of the ACPI 1.0 RSDP.
 const RSDP_V1_LENGTH: usize = 20;
+/// The size in bytes covered by the ACPI 2.0+ extended checksum (mirrors Linux ACPI_RSDP_XCHECKSUM_LENGTH).
+const RSDP_XCHECKSUM_LENGTH: usize = 36;
 /// The total size in bytes of the RSDP fields introduced in ACPI 2.0.
 const RSDP_V2_EXT_LENGTH: usize = mem::size_of::<Rsdp>() - RSDP_V1_LENGTH;
 
@@ -114,10 +116,11 @@ impl Rsdp {
         /*
          * `self.length` doesn't exist on ACPI version 1.0, so we mustn't rely on it. Instead,
          * check for version 1.0 and use a hard-coded length instead.
+         *
+         * For Version 2.0+, use the Linux's ACPI_RSDP_XCHECKSUM_LENGTH.
          */
-        let length = if self.revision > 0 {
-            // For Version 2.0+, include the number of bytes specified by `length`
-            self.length as usize
+        let length = if self.revision > 1 {
+            RSDP_XCHECKSUM_LENGTH
         } else {
             RSDP_V1_LENGTH
         };