Some more 2.6.12 API changes

A few more changes to the 2.6 internal kernel API have been merged since last week's summary.

The driver model API has seen a couple of small changes. kref_put() no longer returns void:

    int kref_put(struct kref *kref, void (*release)(struct kref *kref));

The (new) return value is normally zero, but will be nonzero if the kref was actually removed. Note that a zero return does not imply that the kref is still valid; somebody else may have done the last kref_put() call in the mean time.

The kset type now has its own internal spinlock. That means that a kset is no longer required to be part of a subsystem.

Greg Kroah-Hartman has proposed a rather wider set of changes to the driver model class code. Essentially, he is pushing all users over to a form of the "class_simple" interface, and getting away from the original class implementation, which was hard to use correctly. These changes have not yet been merged, however.

The kernel has long held a variety of special-purpose sorting functions. These have now been replaced by a generic heap sort utility written by Matt Mackall. It's interface is:

    void sort(void *base, size_t num, size_t size, 
              int (*compare)(const void *a, const void *b),
              void (*swap)(void *a, void *b, int size));

Here, base is the array of items to sort; it contains num items of size bytes. The compare() function returns the integer equivalent of a-b; sort() will sort the array in ascending order as dictated by compare(). The swap() function is optional; it can be provided if the caller knows a faster way to exchange two elements in the array.

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