Arguments

Description

cb will be initialized by fence_add_callback, no initialization by the caller is required. Any number of callbacks can be registered to a fence, but a callback can only be registered to one fence at a time.

Note that the callback can be called from an atomic context. If fence is already signaled, this function will return -ENOENT (and *not* call the callback)

Add a software callback to the fence. Same restrictions apply to refcount as it does to fence_wait, however the caller doesn't need to

keep a refcount to fence afterwards

when software access is enabled, the creator of the fence is required to keep the fence alive until after it signals with fence_signal. The callback itself can be called from irq context.