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diff --git a/drivers/block/README.ide b/drivers/block/README.ide new file mode 100644 index 000000000..39ae4fa79 --- /dev/null +++ b/drivers/block/README.ide @@ -0,0 +1,278 @@ +README.ide -- Information regarding ide.c and ide-cd.c (IDE driver in 1.2.x) +================================================================================ +Supported by: mlord@bnr.ca -- disks, interfaces, probing + snyder@fnald0.fnal.gov -- cdroms, ATAPI, audio + +(see description later on below for handling BIG IDE drives with >1024 cyls). + +Major features of ide.c & ide-cd.c: + + - support for up to two IDE interfaces on one or two IRQs + - support for any mix of up to four disk and/or cdrom drives + - support for reading IDE ATAPI cdrom drives (NEC,MITSUMI,VERTOS,SONY) + - support for audio functions + - auto-detection of interfaces, drives, IRQs, and disk geometries + -- "single" drives should be jumpered as "master", not "slave" + - support for BIOSs which report "more than 16 heads" on disk drives + - uses LBA (slightly faster) on disk drives which support it + - support for lots of fancy (E)IDE drive functions with hdparm utility + - optional (compile time) support for 32-bit VLB data transfers + - support for IDE multiple (block) mode (same as hd.c) + - support for interrupt unmasking during I/O (better than hd.c) + - improved handshaking and error detection/recovery + - can co-exist with hd.c to control only the secondary interface +NEW! - support for reliable operation of buggy CMD-640 interfaces + - use kernel command line option: hda=serialize +NEW! - experimental support for DTC-2278D interfaces + - use kernel command line option: hda=dtc2278 +NEW! - run-time selectable 32bit interface support (using hdparm-2.3) + +Under construction: + + - improved CMD support: tech info is supposedly "in the mail" + - support for interface speed selection on jumperless interfaces + - improved detection of non-standard IDE ATAPI cdrom drives + - support for non-standard 3rd/4th drive interface on Promise cards + +*** + +IMPORTANT NOTICE: "CMD" EIDE Interfaces will not (by default) work *reliably* +when drives are attached to the second interface. To "fix" this, supply the +special kernel "command line" parameter to LILO: hda=serialize +Failure to do so can cause severe data corruption! + +*** + +To access devices on the second interface, device entries must first be +created in /dev for them. To create such entries, simply run the included +shell script: MAKEDEV.ide1 + +Apparently the early releases of Slackware 2.2 have incorrect entries +in /dev for hdc* and hdd* -- this can also be corrected by running MAKEDEV.ide1 + +ide.c automatically probes for the primary and secondary interfaces, +for the drives/geometries attached to those interfaces, and for the +IRQ numbers being used by the interfaces (normally IRQ14 & IRQ15). + +The primary and secondary interfaces may share a single IRQ if necessary, +at a slight performance penalty, whether on separate cards or a single VLB card. + +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,hdb,hdc,hdd}, or simply hd, for the "next" drive +in sequence. Only the first three parameters are required (cyls,heads,sects), +and wpcom is ignored for IDE drives. For example: + + hdc=1050,32,64 hdd=cdrom + +If an irq number is given, it will apply to both drives on the same interface, +either {hda,hdb} or {hdc,hdd}. The results of successful auto-probing may +override the physical geometry/irq specified, though the "original" geometry +is retained as the "logical" geometry for partitioning purposes (fdisk). + +If the auto-probing during boot time confuses a drive (ie. the drive works +with hd.c but not with ide.c), then an command line option may be specified +for each drive for which you'd like the drive to skip the hardware +probe/identification sequence. For example: + + hdb=noprobe +or + hdc=768,16,32 + hdc=noprobe + +Note that when only one IDE device is attached to an interface, +it must be jumpered as "single" or "master", *not* "slave". +Many folks have had "trouble" with cdroms because of this requirement +of the ATA (IDE) standard. + +Courtesy of Scott Snyder, the driver now supports ATAPI cdrom drives +such as the NEC-260 and the new MITSUMI triple/quad speed drives. +Such drives will be identified at boot time, as hda,hdb,hdc or hdd, +just like a harddisk. + +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 + +For example, a GW2000 system might have a harddrive on the primary +interface (/dev/hda) and an IDE cdrom drive on the secondary interface +(/dev/hdc). To mount a CD in the cdrom drive, one would use something like: + + ln -sf /dev/hdc /dev/cdrom + mkdir /cd + mount /dev/cdrom /cd -t iso9660 -o ro + +Please pass on any feedback on the cdrom stuff to the author & maintainer, +Scott Snyder (snyder@fnald0.fnal.gov). + +The kernel is now be able to execute binaries directly off of the cdrom, +provided it is mounted with the default block size of 1024. + +The hdparm.c program for controlling various IDE features is now packaged +separately. Look for it on popular linux FTP sites. + +mlord@bnr.ca +snyder@fnald0.fnal.gov +================================================================================ + +Some Terminology +---------------- +IDE = Integrated Drive Electronics, meaning that each drive has a built-in +controller, which is why an "IDE interface card" is not a "controller card". + +IDE drives are designed to attach almost directly to the ISA bus of an AT-style +computer. The typical IDE interface card merely provides I/O port address +decoding and tri-state buffers, although several newer localbus cards go much +beyond the basics. When purchasing a localbus IDE interface, avoid cards with +an onboard BIOS and those which require special drivers. Instead, look for a +card which uses hardware switches/jumpers to select the interface timing speed, +to allow much faster data transfers than the original 8Mhz ISA bus allows. + +ATA = AT (the old IBM 286 computer) Attachment Interface, a draft American +National Standard for connecting hard drives to PCs. This is the official +name for "IDE". + +The latest standards define some enhancements, known as the ATA-2 spec, +which grew out of vendor-specific "Enhanced IDE" (EIDE) implementations. + +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 and TAPE devices, and will +likely also soon be used for Floppy drives, removable R/W cartridges, +and for high capacity hard disk drives. + +How To Use *Big* ATA/IDE drives with Linux +------------------------------------------ +The ATA Interface spec for IDE disk drives allows a total of 28 bits +(8 bits for sector, 16 bits for cylinder, and 4 bits for head) for addressing +individual disk sectors of 512 bytes each (in "Linear Block Address" (LBA) +mode, there is still only a total of 28 bits available in the hardware). +This "limits" the capacity of an IDE drive to no more than 128GB (Giga-bytes). +All current day IDE drives are somewhat smaller than this upper limit, and +within a few years, ATAPI disk drives will raise the limit considerably. + +All IDE disk drives "suffer" from a "16-heads" limitation: the hardware has +only a four bit field for head selection, restricting the number of "physical" +heads to 16 or less. Since the BIOS usually has a 63 sectors/track limit, +this means that all IDE drivers larger than 504MB (528Meg) must use a "physical" +geometry with more than 1024 cylinders. + + (1024cyls * 16heads * 63sects * 512bytes/sector) / (1024 * 1024) == 504MB + +(Some BIOSs (and controllers with onboard BIOS) pretend to allow "32" or "64" + heads per drive (discussed below), but can only do so by playing games with + the real (hidden) geometry, which is always limited to 16 or fewer heads). + +This presents two problems to most systems: + + 1. The INT13 interface to the BIOS only allows 10-bits for cylinder + addresses, giving a limit of 1024cyls for programs which use it. + + 2. The physical geometry fields of the disk partition table only + allow 10-bits for cylinder addresses, giving a similar limit of 1024 + cyls for operating systems that do not use the "sector count" fields + instead of the physical Cyl/Head/Sect (CHS) geometry fields. + +Neither of these limitations affects Linux itself, as it (1) does not use the +BIOS for disk access, and it (2) is clever enough to use the "sector count" +fields of the partition table instead of the physical CHS geometry fields. + + a) Most folks use LILO to load linux. LILO uses the INT13 interface + to the BIOS to load the kernel at boot time. Therefore, LILO can only + load linux if the files it needs (usually just the kernel images) are + located below the magic 1024 cylinder "boundary" (more on this later). + + b) Many folks also like to have bootable DOS partitions on their + drive(s). DOS also uses the INT13 interface to the BIOS, not only + for booting, but also for operation after booting. Therefore, DOS + can normally only access partitions which are contained entirely below + the magic 1024 cylinder "boundary". + +There are at least seven commonly used schemes for kludging DOS to work +around this "limitation". In the long term, the problem is being solved +by introduction of an alternative BIOS interface that does not have the +same limitations as the INT13 interface. New versions of DOS are expected +to detect and use this interface in systems whose BIOS provides it. + +But in the present day, alternative solutions are necessary. + +The most popular solution in newer systems is to have the BIOS shift bits +between the cylinder and head number fields. This is activated by entering +a translated logical geometry into the BIOS/CMOS setup for the drive. +Thus, if the drive has a geometry of 2100/16/63 (CHS), then the BIOS could +present a "logical" geometry of 525/64/63 by "shifting" two bits from the +cylinder number into the head number field for purposes of the partition table, +CMOS setup, and INT13 interfaces. Linux kernels 1.1.39 and higher detect and +"handle" this translation automatically, making this a rather painless solution +for the 1024 cyls problem. If for some reason Linux gets confused (unlikely), +then use the kernel command line parameters to pass the *logical* geometry, +as in: hda=525,64,63 + +If the BIOS does not support this form of drive translation, then several +options remain, listed below in inverse order of popularity: + + - boot from a floppy disk instead of the hard drive (takes 10 seconds). + - use a partition below the 1024 cyl boundary to hold the linux + boot files (kernel images and /boot directory), and place the rest + of linux anywhere else on the drive. These files can reside in a DOS + partition, or in a tailor-made linux boot partition. + +If you cannot use drive translation, *and* your BIOS also restricts you to +entering no more than 1024 cylinders in the geometry field in the CMOS setup, +then just set it to 1024. As of v3.5 of this driver, Linux automatically +determines the *real* number of cylinders for fdisk to use, allowing easy +access to the full disk capacity without having to fiddle around. + +Regardless of what you do, all DOS partitions *must* be contained entirely +within the first 1024 logical cylinders. For a 1Gig WD disk drive, here's +a good "half and half" partitioning scheme to start with: + + geometry = 2100/16/63 + /dev/hda1 from cyl 1 to 992 dos + /dev/hda2 from cyl 993 to 1023 swap + /dev/hda3 from cyl 1024 to 2100 linux + +To ensure that LILO can boot linux, the boot files (kernel and /boot/*) +must reside within the first 1024 cylinders of the drive. If your linux +root partition is *not* completely within the first 1024 cyls (quite common), +then you can use LILO to boot linux from files on your DOS partition +by doing the following after installing slackware (or whatever): + + 0. Boot from the "boot floppy" created during the installation + 1. Mount your DOS partition as /dos (and stick it in /etc/fstab) + 2. Move your kernel (/vmlinuz) to /dos/vmlinuz with: mv /vmlinuz /dos + 3. Edit /etc/lilo.conf to change /vmlinuz to /dos/vmlinuz + 4. Move /boot to /dos/boot with: cp -a /boot /dos ; rm -r /boot + 5. Create a symlink for LILO to use with: ln -s /dos/boot /boot + 6. Re-run LILO with: lilo + + A danger with this approach is that whenever an MS-DOS "defragmentation" + program is run (like Norton "speeddisk"), it may move the Linux boot + files around, confusing LILO and making the (Linux) system unbootable. + Be sure to keep a kernel "boot floppy" at hand for such circumstances. + +If you "don't do DOS", then partition as you please, but remember to create +a small partition to hold the /boot directory (and vmlinuz) as described above +such that they stay within the first 1024 cylinders. + +Note that when creating partitions that span beyond cylinder 1024, +Linux fdisk will complain about "Partition X has different physical/logical +endings" and emit messages such as "This is larger than 1024, and may cause +problems with some software". Ignore them for linux partitions. The "some +software" refers to DOS, the BIOS, and LILO, as described previously. + +Western Digital now ships a "DiskManager 6.03" diskette with all of their big +hard drives. Burn it! That idiotic piece of garbage isn't even universally +compatible with DOS, let alone other operating systems like Linux. Eventually +some kind person will kludge Linux to work with it, but at present the two +are completely incompatible. If you have this version of DiskManager on your +hard disk already, it can be exterminated at the expense of all data on the +drive (back it up elsewhere), by using the "DM" command from the diskette +as follows: DM /Y- + +mlord@bnr.ca |