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A.1. Changes between 2.0 and 2.2
A.1.1. Changes between 2.0 and 2.2
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 located on Richard Gooch's site .
- 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,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 queue_task_irq.
- 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 SMP.
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