Allocate cdemu buffer in low mem instead of ebda.

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.

1 files changed, 18 insertions, 15 deletions

diff --git a/src/cdrom.c b/src/cdrom.c
index f7af425f..655ee00a 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;