[vbox-dev] Patch to PC BIOS file: \src\VBox\Devices\PC\BIOS\floppy.c
Dave Meagher
stope19 at gmail.com
Sun Feb 15 09:07:08 GMT 2015
Hi,
I'd like to contribute a patch to the file:
'\src\VBox\Devices\PC\BIOS\floppy.c'. This patch is submitted under the MIT
License.
The patch provides an implementation for 2 BIOS entry points that are - in
the current source tree - stubbed out as 'not available'. The 2 entry
points are:
Int 13/AH=17h - FLOPPY DISK - SET DISK TYPE FOR FORMAT (AT,PS)
Int 13/AH=18h - FLOPPY DISK - SET MEDIA TYPE FOR FORMAT (AT model
3x9,XT2,XT286,PS)
As mentioned, these are not currently implemented - so I see little risk to
existing software. The patch was developed on a Win32 XP platform, the
usual dev tools and Open Watcom 1.9
The motivation for this patch is a requirement to get an old (early 90's)
database system to load in VirtualBox. It uses these entry points not to
perform format operations, but to setup the floppy for subsequent IO
operations. Why it does this I cannot say...
The patch is in the attached text file, and was created against the current
file image from the source repository.
Regards,
Dave
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--- C:/DOCUME~1/davem/LOCALS~1/Temp/floppy.c-revBASE.svn001.tmp.c Thu Jan 1 01:59:44 2015
+++ C:/svn/src/VBox/Devices/PC/BIOS/floppy.c Sun Feb 15 11:45:52 2015
@@ -450,7 +450,7 @@ void BIOSCALL int13_diskette_function(disk_regs_t
{
uint8_t drive, num_sectors, track, sector, head;
uint16_t base_address, base_count, base_es;
- uint8_t page, mode_register, val8;
+ uint8_t page, mode_register, val8, media_state;
uint8_t return_status[7];
uint8_t drive_type, num_floppies, ah;
uint16_t last_addr;
@@ -1110,17 +1110,195 @@ void BIOSCALL int13_diskette_function(disk_regs_t
case 0x17: // set diskette type for format(old)
BX_DEBUG_INT13_FL("floppy f17\n");
- /* not used for 1.44M floppies */
- SET_AH(0x01); // not supported
- set_diskette_ret_status(1); /* not supported */
- SET_CF();
+ // NOTE: 1.44M diskette not supported by this function, use Int13 ah=0x18 instead.
+ // Ref: http://www.ctyme.com/intr/rb-0641.htm
+ // Drive number (0 or 1) values allowed
+ drive = GET_ELDL();
+
+ // Format type (AL)
+ // 00 - NOT USED
+ // 01 - DISKETTE 360K IN 360K DRIVE
+ // 02 - DISKETTE 360K IN 1.2M DRIVE
+ // 03 - DISKETTE 1.2M IN 1.2M DRIVE
+ // 04 - DISKETTE 720K IN 720K DRIVE
+ val8 = GET_AL();
+
+ BX_DEBUG_INT13_FL("floppy f17 - drive: %d, format type: %d\n", drive, val8);
+
+ if (drive > 1) {
+ SET_AH(0x01); // invalid drive
+ set_diskette_ret_status(0x01); // bad parameter
+ SET_CF();
+ return;
+ }
+
+ // see if drive exists
+ if (floppy_drive_exists(drive) == 0) {
+ SET_AH(0x80); // not responding/time out
+ set_diskette_ret_status(0x80);
+ SET_CF();
+ return;
+ }
+
+ // Get current drive state. Set 'base_address' to media status offset address
+ base_address = (drive) ? 0x0091 : 0x0090;
+ media_state = read_byte(0x0040, base_address);
+
+ // Mask out (clear) bits 4-7 (4:media type established, 5:double stepping, 6-7:data rate)
+ media_state &= 0x0f;
+
+ switch(val8) {
+ case 1:
+ // 360K media in 360K drive
+ media_state |= 0x90; // 1001 0000 (media type established, data rate=250)
+ break;
+ case 2:
+ // 360K media in 1.2M drive
+ media_state |= 0x70; // 0111 0000 (media type established, double stepping, data rate=300)
+ break;
+ case 3:
+ // 1.2M media in 1.2M drive
+ media_state |= 0x10; // 0001 0000 (media type established, data rate=500)
+ break;
+ case 4:
+ // 720K media in 720K drive
+ media_state |= 0x90; // 1001 0000 (media type established, data rate=250)
+ break;
+ default:
+ // bad parameter
+ SET_AH(0x01); // invalid format mode parameter
+ set_diskette_ret_status(0x01);
+ SET_CF();
+ return;
+ }
+
+ // Update media status
+ write_byte(0x0040, base_address, media_state);
+ BX_DEBUG_INT13_FL("floppy f17 - media status set to: %02x\n", media_state);
+
+ // return success!
+ SET_AH(0);
+ set_diskette_ret_status(0);
+ CLEAR_CF();
return;
case 0x18: // set diskette type for format(new)
BX_DEBUG_INT13_FL("floppy f18\n");
- SET_AH(0x01); // do later
- set_diskette_ret_status(1);
- SET_CF();
+ // Set Media Type for Format. Verifies that the device supports a specific geometry.
+ // Unlike Int13 ah=0x17 entry point, this version supports higher capacity
+ // drives like 1.44M and even 2.88M. Ref: http://www.ctyme.com/intr/rb-0643.htm
+ // Drive number (0 or 1) values allowed
+ drive = GET_ELDL();
+
+ val8 = GET_CL();
+ num_sectors = val8 & 0x3f; // max sector number per cylinder
+ track = ((val8 >> 6) << 8) + GET_CH(); // max cylinder number (max cylinders - 1)
+
+ BX_DEBUG_INT13_FL("floppy f18 - drive: %d, max cylinder/track number: %d, sectors-per-tracks: %d\n",
+ drive, track, num_sectors);
+
+ if (drive > 1) {
+ SET_AH(0x01); // invalid drive
+ set_diskette_ret_status(0x01);
+ SET_CF();
+ return;
+ }
+
+ // see if drive exists
+ if (floppy_drive_exists(drive) == 0) {
+ SET_AH(0x80); // not responding/time out
+ set_diskette_ret_status(0x80);
+ SET_CF();
+ return;
+ }
+
+ // see if media in drive, and media type is known
+ if (floppy_media_known(drive) == 0) {
+ if (floppy_media_sense(drive) == 0) {
+ SET_AH(0x0C); // drive/media type unknown
+ set_diskette_ret_status(0x0C);
+ SET_CF();
+ return;
+ }
+ }
+
+ // @todo: break out drive type determination
+ drive_type = inb_cmos(0x10);
+ if (drive == 0)
+ drive_type >>= 4;
+ else
+ drive_type &= 0x0f;
+
+ // Get current drive state. Set 'base_address' to media status offset address
+ base_address = (drive) ? 0x0091 : 0x0090;
+ media_state = read_byte(0x0040, base_address);
+
+ // Mask out (clear) bits 4-7 (4:media type established, 5:double stepping, 6-7:data rate)
+ media_state &= 0x0f;
+
+ switch (drive_type) {
+ case 1: // 360KB, 5.25"
+ if (track == 39 && num_sectors == 9)
+ media_state |= 0x90; // 1001 0000 (media type established, data rate=250)
+
+ break;
+ case 2: // 1.2MB, 5.25"
+ if (track == 39 && num_sectors == 9) { // 360K disk in 1.2M drive
+ media_state |= 0x70; // 0111 0000 (media type established, double stepping, data rate=300)
+ } else if (track == 79 && num_sectors == 15) { // 1.2M disk in 1.2M drive
+ media_state |= 0x10; // 0001 0000 (media type established, data rate=500)
+ }
+ break;
+ case 3: // 720KB, 3.5"
+ if (track == 79 && num_sectors == 9)
+ media_state |= 0x90; // 1001 0000 (media type established, data rate=250)
+
+ break;
+ case 4: // 1.44MB, 3.5"
+ if (track == 79) {
+ if (num_sectors == 9) { // 720K disk in 1.44M drive
+ media_state |= 0x90; // 1001 0000 (media type established, data rate=250)
+ } else if (num_sectors == 18) { // 1.44M disk in 1.44M drive
+ media_state |= 0x10; // 0001 0000 (media type established, data rate=500)
+ }
+ }
+ break;
+ case 5: // 2.88MB, 3.5"
+ if (track == 79) {
+ if (num_sectors == 9) { // 720K disk in 2.88M drive
+ media_state |= 0x90; // 1001 0000 (media type established, data rate=250)
+ } else if (num_sectors == 18) { // 1.44M disk in 2.88M drive
+ media_state |= 0x10; // 0001 0000 (media type established, data rate=500)
+ } else if (num_sectors == 36) { // 2.88M disk in 2.88M drive
+ media_state |= 0xD0; // 1101 0000 (media type established, data rate=1mb/s)
+ }
+ }
+ break;
+ default:
+ break;
+ }
+
+ // Error if bit 4 (media type established) has not just been set above..
+ if (0 == ((media_state >> 4) & 0x01)) {
+ // Error - assume requested tracks/sectors-per-track not supported
+ // for current drive type - or drive type is unknown!
+ SET_AH(0x0C);
+ set_diskette_ret_status(0x0C);
+ SET_CF();
+ return;
+ }
+
+ // Update media status
+ write_byte(0x0040, base_address, media_state);
+
+ // set es & di to point to 11 byte diskette param table in ROM
+ ES = 0xF000; // @todo: any way to make this relocatable?
+ DI = get_floppy_dpt(drive_type);
+
+ // return success!
+ SET_AH(0);
+ set_diskette_ret_status(0);
+ CLEAR_CF();
return;
default:
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