[SeaBIOS] [PATCHv2] support T13 EDD3.0 spec

[Gleb Natapov]

Some guests (such as Linux) expect BIOS to behave according to T13
EDD3.0 spec. T13 spec is much better then Phoenix since it provides
more information about interface and device paths. This patch adds
support for the spec. If guest provides buffer with enough space for
T13 EDD info return EDD according to T13 spec otherwise use Phoenix
one.

Signed-off-by: Gleb Natapov 
diff --git a/src/disk.c b/src/disk.c
index f7bfe9c..5ac69fd 100644
--- a/src/disk.c
+++ b/src/disk.c
@@ -503,6 +503,7 @@ static void
 disk_1348(struct bregs *regs, struct drive_s *drive_g)
 {
     u16 size = GET_INT13DPT(regs, size);
+    u16 t13 = size == 74;

// Buffer is too small
     if (size < 26) {
@@ -553,8 +554,9 @@ disk_1348(struct bregs *regs, struct drive_s *drive_g)
     // EDD 2.x

int bdf;
-    u16 iobase1;
-    u64 device_path;
+    u16 iobase1 = 0;
+    u64 device_path = 0;
+    u8 channel = 0;
     SET_INT13DPT(regs, size, 30);
     if (type == DTYPE_ATA || type == DTYPE_ATAPI) {
         u16 ebda_seg = get_ebda_seg();
@@ -573,6 +575,7 @@ disk_1348(struct bregs *regs, struct drive_s *drive_g)
         iobase1 = GET_GLOBALFLAT(chan_gf->iobase1);
         bdf = GET_GLOBALFLAT(chan_gf->pci_bdf);
         device_path = slave;
+        channel = GET_GLOBALFLAT(chan_gf->chanid);

u16 options = 0;
         if (type == DTYPE_ATA) {
@@ -613,8 +616,6 @@ disk_1348(struct bregs *regs, struct drive_s *drive_g)
         SET_INT13DPT(regs, dpte_segment, 0);
         SET_INT13DPT(regs, dpte_offset, 0);
         bdf = GET_GLOBAL(drive_g->cntl_id);
-        device_path = 0;
-        iobase1 = 0;
     }

if (size < 66) {
@@ -632,17 +633,20 @@ disk_1348(struct bregs *regs, struct drive_s *drive_g)
         SET_INT13DPT(regs, host_bus[0], 'P');
         SET_INT13DPT(regs, host_bus[1], 'C');
         SET_INT13DPT(regs, host_bus[2], 'I');
-        SET_INT13DPT(regs, host_bus[3], 0);
+        SET_INT13DPT(regs, host_bus[3], ' ');

u32 path = (pci_bdf_to_bus(bdf) | (pci_bdf_to_dev(bdf) << 8)
                     | (pci_bdf_to_fn(bdf) << 16));
+        if (t13)
+            path |= channel << 24;
+
         SET_INT13DPT(regs, iface_path, path);
     } else {
         // ISA
         SET_INT13DPT(regs, host_bus[0], 'I');
         SET_INT13DPT(regs, host_bus[1], 'S');
         SET_INT13DPT(regs, host_bus[2], 'A');
-        SET_INT13DPT(regs, host_bus[3], 0);
+        SET_INT13DPT(regs, host_bus[3], ' ');

SET_INT13DPT(regs, iface_path, iobase1);
     }
@@ -651,7 +655,7 @@ disk_1348(struct bregs *regs, struct drive_s *drive_g)
         SET_INT13DPT(regs, iface_type[0], 'A');
         SET_INT13DPT(regs, iface_type[1], 'T');
         SET_INT13DPT(regs, iface_type[2], 'A');
-        SET_INT13DPT(regs, iface_type[3], 0);
+        SET_INT13DPT(regs, iface_type[3], ' ');
     } else {
         SET_INT13DPT(regs, iface_type[0], 'S');
         SET_INT13DPT(regs, iface_type[1], 'C');
@@ -663,10 +667,18 @@ disk_1348(struct bregs *regs, struct drive_s *drive_g)
     SET_INT13DPT(regs, iface_type[6], 0);
     SET_INT13DPT(regs, iface_type[7], 0);

-    SET_INT13DPT(regs, device_path, device_path);
+    if (t13) {
+        SET_INT13DPT(regs, t13.device_path[0], device_path);
+        SET_INT13DPT(regs, t13.device_path[1], 0);
+
+        SET_INT13DPT(regs, t13.checksum
+                     , -checksum_far(regs->ds, (void*)(regs->si+30), 43));
+    } else {
+        SET_INT13DPT(regs, phoenix.device_path, device_path);

-    SET_INT13DPT(regs, checksum
-                 , -checksum_far(regs->ds, (void*)(regs->si+30), 35));
+        SET_INT13DPT(regs, phoenix.checksum
+                     , -checksum_far(regs->ds, (void*)(regs->si+30), 35));
+    }

disk_ret(regs, DISK_RET_SUCCESS);
 }
diff --git a/src/disk.h b/src/disk.h
index f31de73..10a0051 100644
--- a/src/disk.h
+++ b/src/disk.h
@@ -63,9 +63,18 @@ struct int13dpt_s {
     u8  host_bus[4];
     u8  iface_type[8];
     u64 iface_path;
-    u64 device_path;
-    u8  reserved3;
-    u8  checksum;
+    union {
+        struct {
+            u64 device_path;
+            u8  reserved3;
+            u8  checksum;
+        } phoenix;
+        struct {
+            u64 device_path[2];
+            u8  reserved3;
+            u8  checksum;
+        } t13;
+    };
 } PACKED;

#define GET_INT13DPT(regs,var)                                          \
--
    		Gleb.