EDID CVT decode

3 files changed, 85 insertions, 6 deletions

diff --git a/cvt.c b/cvt.c
index edff0a4..d7cd570 100644
--- a/cvt.c
+++ b/cvt.c
@@ -47,7 +47,7 @@
  *
  */
 struct mt_mode *
-mt_ct_mode(int hdisplay, int vdisplay, float vrefresh, uint32_t flags)
+mt_cvt_mode(uint32_t hdisplay, uint32_t vdisplay, float refresh, uint32_t flags)
 {
     struct mt_mode *mode = mt_mode_alloc();
     int interlaced = !!(flags & MT_FLAG_INTERLACED);
@@ -75,14 +75,14 @@ mt_ct_mode(int hdisplay, int vdisplay, float vrefresh, uint32_t flags)
     float  interlace; /* please rename this */
 
     /* CVT default is 60.0Hz */
-    if (!vrefresh)
-        vrefresh = 60.0;
+    if (!refresh)
+        refresh = 60.0;
 
     /* 1. Required field rate */
     if (interlaced)
-        vfieldrate = vrefresh * 2;
+        vfieldrate = refresh * 2;
     else
-        vfieldrate = vrefresh;
+        vfieldrate = refresh;
 
     /* 2. Horizontal pixels */
     hdisplayrnd = hdisplay - (hdisplay % CVT_H_GRANULARITY);
diff --git a/edid.c b/edid.c
index 3913c3a..f8ba728 100644
--- a/edid.c
+++ b/edid.c
@@ -290,6 +290,84 @@ edid_estiii_modes(uint8_t *x)
     return ret;
 }
 
+static uint32_t
+edid_cvt_next_refresh(uint32_t *refreshes, uint32_t *flag)
+{
+    if (*refreshes & 0x10) {
+        *refreshes &= 0x10;
+        return 50;
+    }
+    if (*refreshes & 0x08) {
+        *refreshes &= 0x08;
+        return 60;
+    }
+    if (*refreshes & 0x04) {
+        *refreshes &= 0x04;
+        return 75;
+    }
+    if (*refreshes & 0x02) {
+        *refreshes &= 0x02;
+        return 85;
+    }
+    if (*refreshes &= 0x01) {
+        *refreshes &= 0x01;
+        *flag = MT_FLAG_REDUCED;
+        return 60;
+    }
+
+    *refreshes = 0;
+    return 0;
+}
+
+static struct mt_mode *
+edid_cvt_mode(uint8_t *x)
+{
+    struct mt_mode *ret = NULL;
+    const uint8_t empty[3] = { 0, 0, 0 };
+    uint32_t width, height, refreshes;
+
+    if (!memcmp(x, empty, 3))
+        return NULL;
+
+    height = x[0];
+    height |= (x[1] & 0xf0) << 4;
+    height++;
+    height *= 2;
+
+    switch (x[1] & 0x0c) {
+    case 0x00:
+        width = (height * 4) / 3; break;
+    case 0x04:
+        width = (height * 16) / 9; break;
+    case 0x08:
+        width = (height * 16) / 10; break;
+    case 0x0c:
+        width = (height * 15) / 9; break;
+    }
+
+    refreshes = x[2] & 0x1f;
+
+    while (refreshes) {
+        uint32_t flag = 0;
+        uint32_t refresh = edid_cvt_next_refresh(&refreshes, &flag);
+        ret = mt_modes_add(ret, mt_cvt_mode(width, height, refresh, flag));
+    }
+
+    return ret;
+}
+
+static struct mt_mode *
+edid_cvt_modes(uint8_t *x)
+{
+    struct mt_mode *ret = NULL;
+    int i;
+
+    for (i = 0; i < 4; i++)
+        ret = mt_modes_add(ret, edid_cvt_mode(x + 6 + (i * 3)));
+
+    return ret;
+}
+
 static struct mt_mode *
 edid_do_detailed_mode(uint8_t *x)
 {
@@ -345,6 +423,7 @@ edid_do_detailed_block(uint8_t *x)
         case 0xF7: /* EST III */
             return edid_estiii_modes(x);
         case 0xF8: /* CVT */
+            return edid_cvt_modes(x);
         case 0xFA: /* standard */
         default:
             return NULL;
diff --git a/minitru.h b/minitru.h
index 4256321..db9dae3 100644
--- a/minitru.h
+++ b/minitru.h
@@ -73,7 +73,7 @@ struct mt_mode {
 
 extern struct mt_mode *mt_monitor_mode_list(struct mt_monitor *monitor);
 extern struct mt_mode *mt_dmt_mode_list(void);
-extern struct mt_mode *mt_cvt_mode(uint32_t width, uint32_t height,
+extern struct mt_mode *mt_cvt_mode(uint32_t hdisplay, uint32_t vdisplay,
                                    float refresh, uint32_t flags);
 extern struct mt_mode *mt_gtf_mode(uint32_t width, uint32_t height,
                                    float refresh, uint32_t flags);