Transferring Data

Transferring Data

The device driver executes in the kernel virtual address space, but it must transfer data to and from the address space of a user process. The kernel supplies two kinds of functions for this purpose:

functions that transfer data between driver variables and the address space of the current process
functions that transfer data between driver variables and the buffer described by a uio_t object

Warning: The use of an invalid address in kernel space with any of these functions causes a kernel panic. All functions that reference an address in user process space can sleep, because the page of process space might not be resident in memory. As a result, such functions cannot be used in an interrupt handler, or while holding a basic lock.

General Data Transfer
Transferring Data Through a uio_t Object