Architecture independent level 1 (DDI/DKI).
An iovec structure describes a data storage area for transfer in a uio(9S) structure. Conceptually, it can be thought of as a base address and length specification.
caddr_t iov_base; /* base address of the data storage area */ /* represented by the iovec structure */ int iov_len; /* size of the data storage area in bytes */
Writing Device Drivers