Based on kernel version 3.19. Page generated on 2015-02-13 21:22 EST.
1 SCSI subsystem documentation 2 ============================ 3 The Linux Documentation Project (LDP) maintains a document describing 4 the SCSI subsystem in the Linux kernel (lk) 2.4 series. See: 5 http://www.tldp.org/HOWTO/SCSI-2.4-HOWTO . The LDP has single 6 and multiple page HTML renderings as well as postscript and pdf. 7 It can also be found at: 8 http://web.archive.org/web/*/http://www.torque.net/scsi/SCSI-2.4-HOWTO 9 10 Notes on using modules in the SCSI subsystem 11 ============================================ 12 The scsi support in the linux kernel can be modularized in a number of 13 different ways depending upon the needs of the end user. To understand 14 your options, we should first define a few terms. 15 16 The scsi-core (also known as the "mid level") contains the core of scsi 17 support. Without it you can do nothing with any of the other scsi drivers. 18 The scsi core support can be a module (scsi_mod.o), or it can be built into 19 the kernel. If the core is a module, it must be the first scsi module 20 loaded, and if you unload the modules, it will have to be the last one 21 unloaded. In practice the modprobe and rmmod commands (and "autoclean") 22 will enforce the correct ordering of loading and unloading modules in 23 the SCSI subsystem. 24 25 The individual upper and lower level drivers can be loaded in any order 26 once the scsi core is present in the kernel (either compiled in or loaded 27 as a module). The disk driver (sd_mod.o), cdrom driver (sr_mod.o), 28 tape driver ** (st.o) and scsi generics driver (sg.o) represent the upper 29 level drivers to support the various assorted devices which can be 30 controlled. You can for example load the tape driver to use the tape drive, 31 and then unload it once you have no further need for the driver (and release 32 the associated memory). 33 34 The lower level drivers are the ones that support the individual cards that 35 are supported for the hardware platform that you are running under. Those 36 individual cards are often called Host Bus Adapters (HBAs). For example the 37 aic7xxx.o driver is used to control all recent SCSI controller cards from 38 Adaptec. Almost all lower level drivers can be built either as modules or 39 built into the kernel. 40 41 42 ** There is a variant of the st driver for controlling OnStream tape 43 devices. Its module name is osst.o .