From 66289aa8ecfa07b20bad424eb9860b196641ef52 Mon Sep 17 00:00:00 2001
From: Brett Weiland <brett_weiland@bpcspace.com>
Date: Fri, 19 Mar 2021 10:54:25 -0500
Subject: first commit

---
 src/kernel/libs/acpi.c | 61 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 61 insertions(+)
 create mode 100644 src/kernel/libs/acpi.c

(limited to 'src/kernel/libs/acpi.c')

diff --git a/src/kernel/libs/acpi.c b/src/kernel/libs/acpi.c
new file mode 100644
index 0000000..8bc6a56
--- /dev/null
+++ b/src/kernel/libs/acpi.c
@@ -0,0 +1,61 @@
+#include <acpi.h>
+#include <stdint.h>
+#include <printf.h>
+
+static int RSDP_verify(void *rsdp_pointer) {
+  printf("Verifying potential RSDP at address 0x%p... ", rsdp_pointer);  
+  union rsdp_t *rsdp = rsdp_pointer;
+  uint8_t checksum = 0;
+  char *rsdp_csm_ptr = rsdp_pointer; 
+  int i;
+  if(checksum) return 0;
+  if(rsdp->v1.version) {
+    printf("APCI revision > 2.\n");
+    checksum = 0;
+    printf("len : %i\n", rsdp->v2.len);
+    for(i = 0; i < rsdp->v2.len; i++) {
+      checksum += rsdp_csm_ptr[i];
+    }
+  }
+  else {
+    printf("APCI revision 1.\n");
+    for(i = 0; i <= 20; i++) {
+      checksum += rsdp_csm_ptr[i];
+    }
+  }
+  if(checksum) {
+    return 0;
+    printf("Invalid, searching on.\n");
+  }
+  printf("RSDP Verified!\n");
+  return 1;
+}
+
+// TODO: move these when you gain your sanity
+rsdp_t *find_RSDP() { // finds root descriptor
+  const char sig[9] = "RSD PTR ";
+  uintptr_t *p = (void *)0x040e;
+  uintptr_t *ebda_unshifted = (void *)p;
+
+  // TODO you REALLY need to verify this.
+  void *ebda = (void *)((uintptr_t)ebda_unshifted << (uintptr_t)4 & (uintptr_t)0xfffff); 
+
+
+  for(void *i = ebda; i <= ebda + 64000; i += 16) {
+    if(!(memcmp(sig, i, 8))) {
+      if(RSDP_verify(i)) {
+        return(i);
+      }
+    }
+  }
+
+  for(void *i = (void *)0xe0000; i <= (void *)0xfffff; i += 16) {
+    if(!(memcmp(sig, i, 8))) {
+      if(RSDP_verify(i)) {
+        return(i);
+      }
+    }
+  }
+}
+
+
-- 
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