EDID probe

2 files changed, 35 insertions, 1 deletions

diff --git a/edid.c b/edid.c
index f97d8ad..01072f1 100644
--- a/edid.c
+++ b/edid.c
@@ -1,8 +1,39 @@
 #include "minitru-int.h"
 
+static const uint8_t header[] = {
+    0x00, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x00
+};
+
+static uint32_t
+edid_valid_checksum(uint8_t *x)
+{
+    unsigned char sum = 0;
+    int i;
+    for (i = 0; i < 128; i++)
+            sum += x[i];
+    return !sum;
+}
+
 static uint32_t edid_probe(struct mt_monitor *mon)
 {
-    return 0;
+    uint8_t *block = mon->block;
+    int i, blocks;
+
+    if (mon->len < 128 || mon->len % 128)
+        return 0;
+
+    blocks = block[0x7e] + 1;
+    if (blocks * 128 != mon->len)
+        return 0;
+
+    if (!memcmp(block, header, 8))
+        return 0;
+
+    for (i = 0; i < 128; i++)
+        if (!edid_valid_checksum(block + (i * 128)))
+            return 0;
+
+    return 1;
 }
 
 static struct mt_mode *
diff --git a/monitor.c b/monitor.c
index 0503cee..3263f3f 100644
--- a/monitor.c
+++ b/monitor.c
@@ -12,6 +12,9 @@ mt_create_monitor(void *block, uint32_t len)
     struct mt_monitor *mon = calloc(1, sizeof(*mon));
     int i;
 
+    if (!block || !len)
+        return NULL;
+
     mon->block = block;
     mon->len = len;