MCD(4) BSD Programmer's Manual MCD(4)NAMEmcd - Mitsumi CD-ROM driver
SYNOPSIS
mcd0 at isa? port 0x334 irq 9
DESCRIPTION
The special files /dev/mcd[%d][a-h] and /dev/rmcd[%d][a-h] provide block
and raw access to the Mitsumi CRMC CD-ROM disk drive using its associated
ISA bus controller. This drive has very poor random access performance,
but it can read a string of contiguous blocks a the full disk speed. To
improve the average performance, the driver contains a 32K byte read-
ahead buffer. This buffer is also used to allow random access to the de-
vice, without regard to the 2048 byte physical sector size.
The controller does not support interrupt auto-configuration, so the ker-
nel config file irq specification should contain an explicit interrupt
number, chosen from the set 3, 5, 9, 10, 11, 12 or 15. Make sure the irq
jumper on the card agrees with the config file value (and note that the
jumper for interrupt 2 corresponds to software level 9). On very fast
machines, or machines with light interrupt loading, it is possible to use
the driver without interrupts. To do this, omit the irq specification
from the config file and remove the interrupt jumper. Using the driver
in this mode can cause undetected read errors.
The controller occupies 4 io ports with base port in the range 0x300 to
0x3fc. The port is configured using a dip switch on the controller card.
The driver supports both DMA and non-DMA operation for both the 8-bit and
16-bit versions of the controller.
When no BSD label is present on a loaded CD-ROM, the driver will generate
a default label which defines the `a' and `h' partitions to represent the
entire disk.
To control the audio play functions of the drive, see the library
cdrom(3).
In this experimental version of the driver, the ioctl MCDIOCSETBUF can be
used to change the size of the read-ahead buffer. This command is unsafe
if it is given while there is an outstanding read request, so be careful
to use it only when the drive is idle. The argument is a pointer to an
integer, which must be a multiple of 2048 and less than or equal to 256K
bytes.
DIAGNOSTICS
mcd%d: no disk in drive
Operation failed because the drive is empty, or the door is not shut.
mcd%d: premature status %x %x
mcd%d: unexpected data %x %x
mcd%d: command error %x
mcd%d: too few status bytes: %d
mcd%d: command time out
mcd%d: block %d: read error
These are various errors that can occur when trying to read. Check that
the disk is a CD-ROM, as opposed CD-AUDIO.
FILES
/dev/cdrom
/dev/rcdrom
SEE ALSOcdrom(3)HISTORY
The mcd driver first appeared in BSDI.
BSDI BSD/OS January 14, 1994 2
