From: Gerd Hoffmann <kraxel@redhat.com>
Date: Tue, 19 Mar 2019 11:09:33 +0100
Subject: vbe: add edid support.

Git-commit: a307d0adc50f41787424a9453145293248a1908c

VBE subfunction 0x15, read ddc data.

Add VBE_edid where drivers can fill in a EDID data blob.
If we find valid data there (checking the first two header
bytes), then report the function as supported and hand out
the data.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Bruce Rogers <brogers@suse.com>
---
 vgasrc/vbe.c     | 30 ++++++++++++++++++++++++++++++
 vgasrc/vgautil.h |  1 +
 2 files changed, 31 insertions(+)

diff --git a/roms/seabios/vgasrc/vbe.c b/roms/seabios/vgasrc/vbe.c
index 724c1bad6d7a8f612e05c198223f..66afb011ada034d53b518f8de068 100644
--- a/roms/seabios/vgasrc/vbe.c
+++ b/roms/seabios/vgasrc/vbe.c
@@ -25,6 +25,7 @@ u32 VBE_total_memory VAR16 = 256 * 1024;
 u32 VBE_capabilities VAR16;
 u32 VBE_framebuffer VAR16;
 u16 VBE_win_granularity VAR16;
+u8 VBE_edid[256] VAR16;
 
 static void
 vbe_104f00(struct bregs *regs)
@@ -400,6 +401,34 @@ vbe_104f10(struct bregs *regs)
     regs->ax = 0x004f;
 }
 
+static void
+vbe_104f15(struct bregs *regs)
+{
+    int offset;
+
+    switch (regs->bl) {
+    case 0x00:
+        if (GET_GLOBAL(VBE_edid[0]) != 0x00 ||
+            GET_GLOBAL(VBE_edid[1]) != 0xff)
+            goto err;
+        regs->bx = 0x0103;
+        break;
+    case 0x01:
+        offset = regs->dx * 128;
+        if (offset >= sizeof(VBE_edid))
+            goto err;
+        memcpy_far(regs->es, (void*)(regs->di+0),
+                   get_global_seg(), VBE_edid + offset,
+                   128);
+        break;
+    err:
+    default:
+        regs->ax = 0x014f;
+        return;
+    }
+    regs->ax = 0x004f;
+}
+
 static void
 vbe_104fXX(struct bregs *regs)
 {
@@ -427,6 +456,7 @@ handle_104f(struct bregs *regs)
     case 0x08: vbe_104f08(regs); break;
     case 0x0a: vbe_104f0a(regs); break;
     case 0x10: vbe_104f10(regs); break;
+    case 0x15: vbe_104f15(regs); break;
     default:   vbe_104fXX(regs); break;
     }
 }
diff --git a/roms/seabios/vgasrc/vgautil.h b/roms/seabios/vgasrc/vgautil.h
index a9940402e45bf293f95b29bbdc2c..dd1aa189547a212ae45bae941f61 100644
--- a/roms/seabios/vgasrc/vgautil.h
+++ b/roms/seabios/vgasrc/vgautil.h
@@ -89,6 +89,7 @@ extern u32 VBE_total_memory;
 extern u32 VBE_capabilities;
 extern u32 VBE_framebuffer;
 extern u16 VBE_win_granularity;
+extern u8 VBE_edid[256];
 void handle_104f(struct bregs *regs);
 
 // vgafonts.c