Chapter 10. Lower Level drivers

There are too many SCSI low level drivers to detail in this document. Alternatively the reader is given suggestions of places to look for further information.

The source directory for the SCSI subsystem in the Linux kernel is a good place to start: /usr/src/linux/drivers/scsi. Several drivers have information in a "readme" file: README.<driver_name>. Others have extensive information at the top of their ".c" file This information often includes a version number, change logs and kernel boot time and module load time options. Often the latter information can be found in the installation guides of the various Linux distributions. Sometimes the driver maintainer will have a web site containing the most recent bug fix information. Official maintainers are listed in the /usr/src/linux/MAINTAINERS file. If there is nothing there, look in the relevant ".c" file in the SCSI subsystem directory. Some old drivers have no active maintainers. In such cases posting to the linux-scsi newsgroup may help [see N1].

Lower level drivers can support either of 2 error handling strategies. The older one is considered obsolete while the newer one is often called "new_eh". The advantage of "new_eh" is that it uses a separate kernel thread (named "scsi_eh_<n>") to facilitate error recovery. Both error handling strategies were also available in the lk 2.2 series in which very few adapter drivers used "new_eh". In the lk 2.4 series, more drivers are using it and the plan in the forthcoming lk 2.5 development series is to drop mid level support for the older, obsolete error strategy.

Drew Eckhardt's SCSI-HOWTO document [see reference W7] goes into much more detail about lower level (adapter) drivers than this document. Since that SCSI-HOWTO is 4 years old, some things may have changed and more drivers have been added.