Supported CD-ROM Drives

As with hard disks, Linux's support for a CD-ROM drive depends on the interface through which that CD-ROM drive connects to the PC's motherboard. CD-ROM drives come with three types of interfaces:

IDE or AT Attachment Packet Interface (ATAPI)-ATAPI is a recent specification for accessing and controlling a CD-ROM drive connected to the PC through the AT Attachment (ATA). ATAPI is gaining popularity because it is built on the cheaper IDE interface. (ATA is the new name for IDE.)
Small Computer System Interface (SCSI)-SCSI is popular because of its relatively high data rates and because it can support multiple devices. The only drawback is that you need a relatively expensive SCSI controller card for the PC.
Universal Serial Bus (USB)-USB is a popular interface for attaching various devices from printers to scanners to PCs. There are CD-ROM drives as well as CD-R (recordable CD) and CD-RW (rewritable CD) drives that attach to USB ports. USB CD-R and CD-RW drives are popular because they can be quickly and easily moved between systems. To support USB CD drives, all you need is to enable USB mass storage support in the kernel. This causes the USB CD drives to appear as SCSI drives, but with different device names.
Proprietary interfaces-Many CD-ROM vendors provide their own proprietary interfaces between the CD-ROM drive and the PC's motherboard. Many sound cards include a built-in CD-ROM-drive interface, which is typically proprietary. The problem with proprietary interfaces is that someone has to develop a Linux driver specifically for each interface, whereas with a SCSI interface you can use a SCSI driver to access any SCSI device.

ATAPI CD-ROM Drives

ATA (AT Attachment) is the official ANSI (American National Standards Institute) standard name for the commonplace IDE interface, which is commonly used to connect hard-disk drives to the PC. ATAPI (ATA Packet Interface) is a protocol (similar to SCSI) for controlling storage devices, such as CD-ROM drives and tape drives. Although ATAPI is relatively new, it is rapidly becoming the most popular type of interface for CD-ROM drives, because ATAPI is based on the ATA (or IDE) interface and does not need any expensive controller card or cable. Also, an ATAPI CD-ROM can simply be connected as the second drive on the same interface on which the PC's hard drive is connected. That means that the ATAPI CD-ROM drive does not require a separate interface card.

The Linux kernel includes an ATAPI driver that should work with any ATAPI CD-ROM drive. ATAPI CD-ROM drives are available from many vendors, such as Aztech, Mitsumi, NEC, Philips, Sony, and Toshiba. Most new PCs (such as those from Gateway and Dell) come configured with ATAPI CD-ROM drives.

Insider Insight

Linux also comes with the ide-scsi driver that emulates a SCSI interface for IDE devices. In Linux IDE CD-R (CD-recordable) or CD-RW (CD-rewritable) drives work through the SCSI emulation driver (ide-scsi). If you have an IDE CD-R or CD-RW drive, add the following line to the /etc/modules.conf file:

alias scsi_hostadapter ide-scsi

SCSI CD-ROM Drives

Linux supports a SCSI CD-ROM drive connected to one of the supported SCSI controller cards (see Appendix B for more information). The only restriction is that the block size (for data transfers) of the SCSI CD-ROM drive should be 512 or 2,048 bytes, which covers all CD-ROM drives on the market.

Some CD-ROM drives include a controller with a modified interface that's not fully SCSI-compatible. These interfaces are essentially proprietary, and you cannot use such CD-ROM drives with the SCSI driver.

SCSI CD-ROM drives are available from many vendors, such as Plextor, Sanyo, and Toshiba.

Proprietary CD-ROM Drives

Although the ATAPI and SCSI CD-ROM drives fall into neat categories and work well in Linux, the situation is much more confusing when it comes to CD-ROM drives with a proprietary interface. Following are two of the biggest sources of confusion:

Some vendors, such as Creative Labs (of SoundBlaster fame), have sold CD-ROM drives with all types of interfaces: ATAPI, SCSI, and proprietary interfaces on a sound card. Thus, the vendor's name alone does not mean anything; you have to know what type of interface the CD-ROM drive uses.
PC vendors sometimes categorize the CD-ROM-drive interface as IDE, even though the interface is really proprietary. Like the IDE (or ATAPI) interface, the proprietary CD-ROM-drive interface is cheap and popular.

As you may have guessed, proprietary CD-ROM-drive interfaces are popular because they tend to be much simpler than SCSI interfaces, which were the primary alternative to proprietary interfaces before ATAPI came along. Because of the popularity of the relatively inexpensive ATAPI, most new PCs do not use proprietary interfaces for CD-ROM drives. Because a proprietary CD-ROM interface can be built into a sound card at little cost, however, some Linux users may have PCs with proprietary CD-ROM drives.

Insider Insight

If you have a choice, avoid proprietary CD-ROM-drive interfaces. They're more trouble than they're worth. Of course, if you have an older PC with a proprietary CD-ROM interface, you may be stuck with it.

Table C-1 lists CD-ROM drives with proprietary interfaces and the drivers you need to support those drives.

Table C-1: CD-ROM Drives with Proprietary Interfaces
Driver	CD-ROM Drive
aztcd	Aztech CDA268-01A (other models are ATAPI drives), Orchid CDS-3110, Okano/Wearnes CDD-110, Conrad TXC, CyCDROM CR520ie/CR940ie
cdu31a	Sony CDU31A/CDU33A
cm206cd	Philips/LMS CM 206
gscd	GoldStar R420 (may be sold as part of the Reveal Multimedia kit)
isp16	CD-ROM drives attached to the interface on an ISP16, MAD16, or Mozart sound card
mcd	Mitsumi CRMC LU005S, FX001
mcdx	Mitsumi CRMC LU005S, FX001 (new driver)
optcd	Optics Storage Dolphin 8000AT, Lasermate CR328A
sbpcd	Matsushita/Panasonic (Panasonic CR-521, CR-522, CR-523, CR-562, and CR-563), Kotobuki, Creative Labs (CD-200), Longshine LCS-7260, Teac CD-55A
sjcd	Sanyo H94A
sonycd535	Sony CDU-535/CDU-531

Linux uses a unique device name for each type of proprietary CD-ROM interface. The CD-ROM devices are block devices like the disk devices, such as /dev/hda and /dev/sda. Table C-2 lists the CD-ROM device names for the proprietary CD-ROM interfaces.

Table C-2: CD-ROM Device Names for Proprietary Interfaces
Device Name	CD-ROM Type
/dev/aztcd	Aztech CD-ROM drive interface
/dev/cdu31a	Sony CDU31A/CDU33A CD-ROM drive interface
/dev/cm206cd	Philips/LMS CD-ROM drive interface
/dev/gscd	GoldStar CD-ROM interface
/dev/hdc	ATAPI CD-ROM drive on the secondary IDE interface on an EIDE controller
/dev/mcd	Mitsumi CD-ROM drive interface
/dev/optcd	Optics Storage CD-ROM drive interface
/dev/sbpcd	Sound Blaster Pro CD-ROM drive interface
/dev/sjcd	Sanyo CD-ROM drive interface
/dev/sonycd535	Sony CDU-535/CDU-531 CD-ROM drive interface