Implement cdrom disk emulation at high-level instead of in low-level ATA.

Add a 2K buffer to the ebda to allow for cdrom 512 byte vs 2048 byte
    sector emulation.
For unaliagned cdemu reads, just make multiple cdrom reads instead of
    using ata specific code for short reads.
Also, define cdemu virtual sectors using struct chs_s, and update
    legacy_lba() func to take pointer to a chs_s struct.

1 files changed, 69 insertions, 32 deletions

diff --git a/src/disk.c b/src/disk.c
index e56bcd0..441db5c 100644
--- a/src/disk.c
+++ b/src/disk.c
@@ -59,9 +59,7 @@ __send_disk_op(struct disk_op_s *op_far, u16 op_seg)
     if (!dop.command)
         // If verify or seek
         status = 0;
-    if (dop.command == CMD_CDEMU_READ)
-        status = cdrom_read_512(&dop);
-    else if (dop.command == CMD_CDROM_READ)
+    if (dop.command == CMD_CDROM_READ)
         status = cdrom_read(&dop);
     else
         status = ata_cmd_data(&dop);
@@ -69,7 +67,8 @@ __send_disk_op(struct disk_op_s *op_far, u16 op_seg)
     irq_disable();
 
     // Update count with total sectors transferred.
-    SET_FARVAR(op_seg, op_far->count, GET_EBDA(sector_count));
+    if (dop.command)
+        SET_FARVAR(op_seg, op_far->count, GET_EBDA(sector_count));
 
     if (status)
         dprintf(1, "disk_op cmd %d error %d!\n", dop.command, status);
@@ -89,20 +88,24 @@ send_disk_op(struct disk_op_s *op)
 
 // Obtain the requested disk lba from an old-style chs request.
 static int
-legacy_lba(struct bregs *regs, struct disk_op_s *op, u16 nlc, u16 nlh, u16 nlspt)
+legacy_lba(struct bregs *regs, u16 lchs_seg, struct chs_s *lchs_far)
 {
-    op->count = regs->al;
+    u8 count = regs->al;
     u16 cylinder = regs->ch | ((((u16)regs->cl) << 2) & 0x300);
     u16 sector = regs->cl & 0x3f;
     u16 head = regs->dh;
 
-    if (op->count > 128 || op->count == 0 || sector == 0) {
+    if (count > 128 || count == 0 || sector == 0) {
         dprintf(1, "int13_harddisk: function %02x, parameter out of range!\n"
                 , regs->ah);
         disk_ret(regs, DISK_RET_EPARAM);
         return -1;
     }
 
+    u16 nlc = GET_FARVAR(lchs_seg, lchs_far->cylinders);
+    u16 nlh = GET_FARVAR(lchs_seg, lchs_far->heads);
+    u16 nlspt = GET_FARVAR(lchs_seg, lchs_far->spt);
+
     // sanity check on cyl heads, sec
     if (cylinder >= nlc || head >= nlh || sector > nlspt) {
         dprintf(1, "int13_harddisk: function %02x, parameters out of"
@@ -113,14 +116,8 @@ legacy_lba(struct bregs *regs, struct disk_op_s *op, u16 nlc, u16 nlh, u16 nlspt
     }
 
     // translate lchs to lba
-    op->lba = (((((u32)cylinder * (u32)nlh) + (u32)head) * (u32)nlspt)
-               + (u32)sector - 1);
-
-    u16 segment = regs->es;
-    u16 offset  = regs->bx;
-    op->buf_fl = MAKE_FLATPTR(segment, offset);
-
-    return 0;
+    return (((((u32)cylinder * (u32)nlh) + (u32)head) * (u32)nlspt)
+            + (u32)sector - 1);
 }
 
 // Perform read/write/verify using old-style chs accesses
@@ -130,12 +127,12 @@ basic_access(struct bregs *regs, u8 device, u16 command)
     struct disk_op_s dop;
     dop.driveid = device;
     dop.command = command;
-    u16 nlc = GET_GLOBAL(ATA.devices[device].lchs.cylinders);
-    u16 nlh = GET_GLOBAL(ATA.devices[device].lchs.heads);
-    u16 nlspt = GET_GLOBAL(ATA.devices[device].lchs.spt);
-    int ret = legacy_lba(regs, &dop, nlc, nlh, nlspt);
-    if (ret)
+    int lba = legacy_lba(regs, get_global_seg(), &ATA.devices[device].lchs);
+    if (lba < 0)
         return;
+    dop.lba = lba;
+    dop.count = regs->al;
+    dop.buf_fl = MAKE_FLATPTR(regs->es, regs->bx);
 
     int status = send_disk_op(&dop);
 
@@ -154,25 +151,65 @@ cdemu_access(struct bregs *regs, u8 device, u16 command)
 {
     struct disk_op_s dop;
     dop.driveid = device;
-    dop.command = (command == ATA_CMD_READ_SECTORS ? CMD_CDEMU_READ : 0);
+    dop.command = (command == ATA_CMD_READ_SECTORS ? CMD_CDROM_READ : 0);
     u16 ebda_seg = get_ebda_seg();
-    u16 nlc = GET_EBDA2(ebda_seg, cdemu.cylinders);
-    u16 nlh = GET_EBDA2(ebda_seg, cdemu.heads);
-    u16 nlspt = GET_EBDA2(ebda_seg, cdemu.spt);
-    int ret = legacy_lba(regs, &dop, nlc, nlh, nlspt);
-    if (ret)
+    int vlba = legacy_lba(
+        regs, ebda_seg
+        , (void*)offsetof(struct extended_bios_data_area_s, cdemu.lchs));
+    if (vlba < 0)
         return;
-    dop.lba += GET_EBDA2(ebda_seg, cdemu.ilba) * 4;
+    dop.lba = GET_EBDA2(ebda_seg, cdemu.ilba) + vlba / 4;
+    u8 count = regs->al;
+    u8 *cdbuf_far = (void*)offsetof(struct extended_bios_data_area_s, cdemu_buf);
+    u8 *dest_far = (void*)(regs->bx+0);
+    regs->al = 0;
 
-    int status = send_disk_op(&dop);
+    if (vlba & 3) {
+        dop.count = 1;
+        dop.buf_fl = MAKE_FLATPTR(ebda_seg, cdbuf_far);
+        int status = send_disk_op(&dop);
+        if (status)
+            goto fail;
+        u8 thiscount = 4 - (vlba & 3);
+        if (thiscount > count)
+            thiscount = count;
+        count -= thiscount;
+        memcpy_far(regs->es, dest_far
+                   , ebda_seg, cdbuf_far + (vlba & 3) * 512
+                   , thiscount * 512);
+        dest_far += thiscount * 512;
+        regs->al += thiscount;
+        dop.lba++;
+    }
 
-    regs->al = dop.count;
+    if (count > 3) {
+        dop.count = count / 4;
+        dop.buf_fl = MAKE_FLATPTR(regs->es, dest_far);
+        int status = send_disk_op(&dop);
+        regs->al += dop.count * 4;
+        if (status)
+            goto fail;
+        u8 thiscount = count & ~3;
+        count &= 3;
+        dest_far += thiscount * 512;
+        dop.lba += thiscount / 4;
+    }
 
-    if (status) {
-        disk_ret(regs, DISK_RET_EBADTRACK);
-        return;
+    if (count) {
+        dop.count = 1;
+        dop.buf_fl = MAKE_FLATPTR(ebda_seg, cdbuf_far);
+        int status = send_disk_op(&dop);
+        if (status)
+            goto fail;
+        u8 thiscount = count;
+        memcpy_far(regs->es, dest_far, ebda_seg, cdbuf_far, thiscount * 512);
+        regs->al += thiscount;
     }
+
     disk_ret(regs, DISK_RET_SUCCESS);
+    return;
+fail:
+    disk_ret(regs, DISK_RET_EBADTRACK);
 }
 
 // Perform read/write/verify using new-style "int13ext" accesses.