ATA/ATAPI/MFM/RLL support

UnixGG1984

  These text are copied from the ide.txt in the directory Documents in kernel source root directory.I consider these important to me, so  I  post these on  my blog.
- If possible devices should be attached to separate channels if they are
  available. Typically the disk on the first and CD-ROM on the second.
- If you mix devices on the same cable, please consider using similar devices  in respect of the data transfer mode they support.
- Even better try to stick to the same vendor and device type on the same
  cable.
It supports up to 9 IDE interfaces per default, on one or more IRQs (usually
14 & 15).  There can be up to two drives per interface, as per the ATA-6 spec.
Primary:    ide0, port 0x1f0; major=3;  hda is minor=0; hdb is minor=64
Secondary:  ide1, port 0x170; major=22; hdc is minor=0; hdd is minor=64
Tertiary:   ide2, port 0x1e8; major=33; hde is minor=0; hdf is minor=64
Quaternary: ide3, port 0x168; major=34; hdg is minor=0; hdh is minor=64
fifth..     ide4, usually PCI, probed
sixth..     ide5, usually PCI, probed
To access devices on interfaces > ide0, device entries please make sure that
device files for them are present in /dev.  If not, please create such
entries, by using /dev/MAKEDEV.
Drives are normally found by auto-probing and/or examining the CMOS/BIOS data.
For really weird situations, the apparent (fdisk) geometry can also be specified
on the kernel "command line" using LILO.  The format of such lines is:
        hdx=cyls,heads,sects,wpcom,irq
or      hdx=cdrom
where hdx can be any of hda through hdh, Three values are required
(cyls,heads,sects).  For example:
        hdc=1050,32,64  hdd=cdrom
either {hda,hdb} or {hdc,hdd}.  The results of successful auto-probing may
override the physical geometry/irq specified, though the "original" geometry
may be retained as the "logical" geometry for partitioning purposes (fdisk).
Note that when only one IDE device is attached to an interface, it should bejumpered as "single" or "master", *not* "slave".
If for some reason your cdrom drive is *not* found at boot time, you can force
the probe to look harder by supplying a kernel command line parameter
via LILO, such as:
        hdc=cdrom       /* hdc = "master" on second interface */
or
        hdd=cdrom       /* hdd = "slave" on second interface */
Note that if BOTH hd.c and ide.c are configured into the kernel,
hd.c will normally be allowed to control the primary IDE interface.
This is useful for older hardware that may be incompatible with ide.c,
and still allows newer hardware to run on the 2nd/3rd/4th IDE ports
under control of ide.c.   To have ide.c also "take over" the primary
IDE port in this situation, use the "command line" parameter:  ide0=0x1f0
ATAPI = ATA Packet Interface, a new protocol for controlling the drives,
similar to SCSI protocols, created at the same time as the ATA2 standard.
ATAPI is currently used for controlling CDROM, TAPE and FLOPPY (ZIP orLS120/240) devices, removable R/W cartridges, and for high capacity hard diskdrives.


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