I don't know the entire kernel well enough do document all of the changes.
In the course of converting the examples (or actually, adapting
Emmanuel Papirakis's changes) I came across the following differences. I
listed all of them here together to help module programmers, especially those
who learned from previous versions of this book and are most familiar with
the techniques I use, convert to the new version.
An additional resource for people who wish to convert to 2.2 is in
asm/uaccess.h If you need put_user
or get_user you have to #include it.
get_user In version 2.2, get_user receives both the
pointer into user memory and the variable in kernel memory to fill
with the information. The reason for this is that get_user
can now read two or four bytes at a time if the variable we read
is two or four bytes long.
file_operations This structure now has a flush function between
the open and close functions.
close in file_operations In version 2.2, the close
function returns an integer, so it's allowed to fail.
read and write in file_operations The headers
for these functions changed. They now return ssize_t instead
of an integer, and their parameter list is different. The inode
is no longer a parameter, and on the other hand the offset into
the file is.
proc_register_dynamic This function no longer exists. Instead,
you call the regular proc_register and put zero in the inode
field of the structure.
Signals The signals in the task structure are no longer a 32 bit
integer, but an array of _NSIG_WORDS integers.
queue_task_irq Even if you want to scheduale a task to happen
from inside an interrupt handler, you use queue_task, not
Module Parameters You no longer just declare module parameters
as global variables. In 2.2 you have to also use MODULE_PARM
to declare their type. This is a big improvement, because it allows
the module to receive string parameters which start with a digits,
for example, without getting confused.
Symmetrical Multi-Processing The kernel is no longer inside one
huge spinlock, which means that kernel modules have to be aware of