FreeBSD Device Drivers

A Straightforward Example

Example 2-2 modifies Example 2-1 to use contigmalloc and contigfree instead of malloc and free. Example 2-2 should clarify any misunderstandings you may have about contigmalloc and contigfree.

Note

To save space, the functions echo_open, echo_close, echo_write, and echo_read aren’t listed here, as they haven’t been changed.

Example 2-2. echo_contig.c

#include <sys/param.h> #include <sys/module.h> #include <sys/kernel.h> #include <sys/systm.h> #include <sys/conf.h> #include <sys/uio.h> #include <sys/malloc.h> #define BUFFER_SIZE 256 MALLOC_DEFINE(M_ECHO, "echo_buffer", "buffer for echo driver"); static d_open_t echo_open; static d_close_t echo_close; static d_read_t echo_read; static d_write_t echo_write; static struct cdevsw ...