default or selected kernelversion does not have config value CONFIG_CHR_DEV_OSST.
Result is shown for kernelversion 6.9.9

SCSI OnStream SC-x0 tape support

modulename: osst.ko

configname: CONFIG_CHR_DEV_OSST

Linux Kernel Configuration
└─>Device Drivers
└─>SCSI device support
└─>SCSI OnStream SC-x0 tape support
In linux kernel since version 2.6.20 (release Date: 2007-02-04)  
The OnStream SC-x0 SCSI tape drives cannot be driven by the
standard st driver, but instead need this special osst driver and
use the /dev/osstX char device nodes (major 206). Via usb-storage,
you may be able to drive the USB-x0 and DI-x0 drives as well.
Note that there is also a second generation of OnStream
tape drives (ADR-x0) that supports the standard SCSI-2 commands for
tapes (QIC-157) and can be driven by the standard driver st.
For more information, you may have a look at the SCSI-HOWTO
<http://www.tldp.org/docs.html#howto> and
<file:Documentation/scsi/osst.txt> in the kernel source.
More info on the OnStream driver may be found on
<http://sourceforge.net/projects/osst/>
Please also have a look at the standard st docu, as most of it
applies to osst as well.

To compile this driver as a module, choose M here and read
<file:Documentation/scsi/scsi.txt>. The module will be called osst.

source code:
depends
CONFIG_SCSI