1*4882a593Smuzhiyun.. SPDX-License-Identifier: GPL-2.0 2*4882a593Smuzhiyun 3*4882a593Smuzhiyun============================ 4*4882a593SmuzhiyunSCSI subsystem documentation 5*4882a593Smuzhiyun============================ 6*4882a593Smuzhiyun 7*4882a593SmuzhiyunThe Linux Documentation Project (LDP) maintains a document describing 8*4882a593Smuzhiyunthe SCSI subsystem in the Linux kernel (lk) 2.4 series. See: 9*4882a593Smuzhiyunhttp://www.tldp.org/HOWTO/SCSI-2.4-HOWTO . The LDP has single 10*4882a593Smuzhiyunand multiple page HTML renderings as well as postscript and pdf. 11*4882a593SmuzhiyunIt can also be found at: 12*4882a593Smuzhiyunhttp://web.archive.org/web/%2E/http://www.torque.net/scsi/SCSI-2.4-HOWTO 13*4882a593Smuzhiyun 14*4882a593SmuzhiyunNotes on using modules in the SCSI subsystem 15*4882a593Smuzhiyun============================================ 16*4882a593SmuzhiyunThe scsi support in the linux kernel can be modularized in a number of 17*4882a593Smuzhiyundifferent ways depending upon the needs of the end user. To understand 18*4882a593Smuzhiyunyour options, we should first define a few terms. 19*4882a593Smuzhiyun 20*4882a593SmuzhiyunThe scsi-core (also known as the "mid level") contains the core of scsi 21*4882a593Smuzhiyunsupport. Without it you can do nothing with any of the other scsi drivers. 22*4882a593SmuzhiyunThe scsi core support can be a module (scsi_mod.o), or it can be built into 23*4882a593Smuzhiyunthe kernel. If the core is a module, it must be the first scsi module 24*4882a593Smuzhiyunloaded, and if you unload the modules, it will have to be the last one 25*4882a593Smuzhiyununloaded. In practice the modprobe and rmmod commands (and "autoclean") 26*4882a593Smuzhiyunwill enforce the correct ordering of loading and unloading modules in 27*4882a593Smuzhiyunthe SCSI subsystem. 28*4882a593Smuzhiyun 29*4882a593SmuzhiyunThe individual upper and lower level drivers can be loaded in any order 30*4882a593Smuzhiyunonce the scsi core is present in the kernel (either compiled in or loaded 31*4882a593Smuzhiyunas a module). The disk driver (sd_mod.o), cdrom driver (sr_mod.o), 32*4882a593Smuzhiyuntape driver [1]_ (st.o) and scsi generics driver (sg.o) represent the upper 33*4882a593Smuzhiyunlevel drivers to support the various assorted devices which can be 34*4882a593Smuzhiyuncontrolled. You can for example load the tape driver to use the tape drive, 35*4882a593Smuzhiyunand then unload it once you have no further need for the driver (and release 36*4882a593Smuzhiyunthe associated memory). 37*4882a593Smuzhiyun 38*4882a593SmuzhiyunThe lower level drivers are the ones that support the individual cards that 39*4882a593Smuzhiyunare supported for the hardware platform that you are running under. Those 40*4882a593Smuzhiyunindividual cards are often called Host Bus Adapters (HBAs). For example the 41*4882a593Smuzhiyunaic7xxx.o driver is used to control all recent SCSI controller cards from 42*4882a593SmuzhiyunAdaptec. Almost all lower level drivers can be built either as modules or 43*4882a593Smuzhiyunbuilt into the kernel. 44*4882a593Smuzhiyun 45*4882a593Smuzhiyun.. [1] There is a variant of the st driver for controlling OnStream tape 46*4882a593Smuzhiyun devices. Its module name is osst.o . 47*4882a593Smuzhiyun 48