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diff --git a/Documentation/scsi/scsi.rst b/Documentation/scsi/scsi.rst new file mode 100644 index 000000000..276918eb4 --- /dev/null +++ b/Documentation/scsi/scsi.rst @@ -0,0 +1,47 @@ +.. SPDX-License-Identifier: GPL-2.0 + +============================ +SCSI subsystem documentation +============================ + +The Linux Documentation Project (LDP) maintains a document describing +the SCSI subsystem in the Linux kernel (lk) 2.4 series. See: +http://www.tldp.org/HOWTO/SCSI-2.4-HOWTO . The LDP has single +and multiple page HTML renderings as well as postscript and pdf. +It can also be found at: +http://web.archive.org/web/%2E/http://www.torque.net/scsi/SCSI-2.4-HOWTO + +Notes on using modules in the SCSI subsystem +============================================ +The scsi support in the linux kernel can be modularized in a number of +different ways depending upon the needs of the end user. To understand +your options, we should first define a few terms. + +The scsi-core (also known as the "mid level") contains the core of scsi +support. Without it you can do nothing with any of the other scsi drivers. +The scsi core support can be a module (scsi_mod.o), or it can be built into +the kernel. If the core is a module, it must be the first scsi module +loaded, and if you unload the modules, it will have to be the last one +unloaded. In practice the modprobe and rmmod commands (and "autoclean") +will enforce the correct ordering of loading and unloading modules in +the SCSI subsystem. + +The individual upper and lower level drivers can be loaded in any order +once the scsi core is present in the kernel (either compiled in or loaded +as a module). The disk driver (sd_mod.o), cdrom driver (sr_mod.o), +tape driver [1]_ (st.o) and scsi generics driver (sg.o) represent the upper +level drivers to support the various assorted devices which can be +controlled. You can for example load the tape driver to use the tape drive, +and then unload it once you have no further need for the driver (and release +the associated memory). + +The lower level drivers are the ones that support the individual cards that +are supported for the hardware platform that you are running under. Those +individual cards are often called Host Bus Adapters (HBAs). For example the +aic7xxx.o driver is used to control all recent SCSI controller cards from +Adaptec. Almost all lower level drivers can be built either as modules or +built into the kernel. + +.. [1] There is a variant of the st driver for controlling OnStream tape + devices. Its module name is osst.o . + |