Currently (at least up to kernel
version 1.1.68) input and output sizes have to be less than or
equal than 4096 bytes unless the kernel has been compiled with
SG_BIG_BUFF defined, if which case it is limited to
SG_BIG_BUFF (e.g. 32768) bytes. These sizes include
the generic header as well as the command block on input.
SG_BIG_BUFF can be safely increased upto (131072 -
512). To take advantage of this, a new kernel has to be compiled
and booted, of course.
The default timeout value is set to one minute
(Timeout = 6000). It can be changed through an ioctl
call (see section sec-ioctl ). The
default number of retries is one.