[PATCH] Allocate cdemu buffer in low mem instead of ebda.

[Kevin O'Connor]

Using the low memory buffer gives more flexibility with the final
location of the buffer.

Don't allocate the buffer at all if no cdrom drives are present.
---
 src/biosvar.h |    2 --
 src/cdrom.c   |   33 ++++++++++++++++++---------------
 src/post.c    |    2 +-
 3 files changed, 19 insertions(+), 18 deletions(-)

diff --git a/src/biosvar.h b/src/biosvar.h
index ea2d67d..dce35af 100644
--- a/src/biosvar.h
+++ b/src/biosvar.h
@@ -234,8 +234,6 @@ struct extended_bios_data_area_s {

// Stack space available for code that needs it.
     u8 extra_stack[512] __aligned(8);
-
-    u8 cdemu_buf[2048 * !!CONFIG_CDROM_EMU];
 } PACKED;

// The initial size and location of EBDA
diff --git a/src/cdrom.c b/src/cdrom.c
index f7af425..655ee00 100644
--- a/src/cdrom.c
+++ b/src/cdrom.c
@@ -17,6 +17,9 @@
  * CD emulation
  ****************************************************************/

+struct drive_s *cdemu_drive_gf VAR16VISIBLE;
+u8 *cdemu_buf_fl VAR16VISIBLE;
+
 static int
 cdemu_read(struct disk_op_s *op)
 {
@@ -30,12 +33,12 @@ cdemu_read(struct disk_op_s *op)

int count = op->count;
     op->count = 0;
-    u8 *cdbuf_far = (void*)offsetof(struct extended_bios_data_area_s, cdemu_buf);
+    u8 *cdbuf_fl = GET_GLOBAL(cdemu_buf_fl);

if (op->lba & 3) {
         // Partial read of first block.
         dop.count = 1;
-        dop.buf_fl = MAKE_FLATPTR(ebda_seg, cdbuf_far);
+        dop.buf_fl = cdbuf_fl;
         int ret = process_op(&dop);
         if (ret)
             return ret;
@@ -43,10 +46,7 @@ cdemu_read(struct disk_op_s *op)
         if (thiscount > count)
             thiscount = count;
         count -= thiscount;
-        memcpy_far(FLATPTR_TO_SEG(op->buf_fl)
-                   , (void*)FLATPTR_TO_OFFSET(op->buf_fl)
-                   , ebda_seg, cdbuf_far + (op->lba & 3) * 512
-                   , thiscount * 512);
+        memcpy_fl(op->buf_fl, cdbuf_fl + (op->lba & 3) * 512, thiscount * 512);
         op->buf_fl += thiscount * 512;
         op->count += thiscount;
         dop.lba++;
@@ -69,14 +69,12 @@ cdemu_read(struct disk_op_s *op)
     if (count) {
         // Partial read on last block.
         dop.count = 1;
-        dop.buf_fl = MAKE_FLATPTR(ebda_seg, cdbuf_far);
+        dop.buf_fl = cdbuf_fl;
         int ret = process_op(&dop);
         if (ret)
             return ret;
         u8 thiscount = count;
-        memcpy_far(FLATPTR_TO_SEG(op->buf_fl)
-                   , (void*)FLATPTR_TO_OFFSET(op->buf_fl)
-                   , ebda_seg, cdbuf_far, thiscount * 512);
+        memcpy_fl(op->buf_fl, cdbuf_fl, thiscount * 512);
         op->count += thiscount;
     }

@@ -106,22 +104,27 @@ process_cdemu_op(struct disk_op_s *op)
     }
 }

-struct drive_s *cdemu_drive_gf VAR16VISIBLE;
-
 void
 cdemu_setup(void)
 {
     if (!CONFIG_CDROM_EMU)
         return;
+    cdemu_drive_gf = NULL;
+    cdemu_buf_fl = NULL;
+    if (!Drives.cdcount)
+        return;

struct drive_s *drive_g = malloc_fseg(sizeof(*drive_g));
-    if (! drive_g) {
+    u8 *buf = malloc_low(CDROM_SECTOR_SIZE);
+    if (!drive_g || !buf) {
         warn_noalloc();
-        cdemu_drive_gf = NULL;
+        free(drive_g);
+        free(buf);
         return;
     }
-    memset(drive_g, 0, sizeof(*drive_g));
     cdemu_drive_gf = drive_g;
+    cdemu_buf_fl = buf;
+    memset(drive_g, 0, sizeof(*drive_g));
     drive_g->type = DTYPE_CDEMU;
     drive_g->blksize = DISK_SECTOR_SIZE;
     drive_g->sectors = (u64)-1;
diff --git a/src/post.c b/src/post.c
index 25535e2..fc7acc5 100644
--- a/src/post.c
+++ b/src/post.c
@@ -217,7 +217,6 @@ post(void)
     // Initialize internal tables
     boot_setup();
     drive_setup();
-    cdemu_setup();

// Start hardware initialization (if optionrom threading)
     if (CONFIG_THREADS && CONFIG_THREAD_OPTIONROMS)
@@ -250,6 +249,7 @@ post(void)
     boot_prep();

// Finalize data structures before boot
+    cdemu_setup();
     pmm_finalize();
     malloc_finalize();
     memmap_finalize();