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dma-buf: clarify dma_fence_add_callback documentation

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That the caller doesn't need to keep a reference is rather
risky and not defensive at all.

Especially dma_buf_poll got that horrible wrong, so better
remove that sentence and also clarify that the callback
might be called in atomic or interrupt context.

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20210901120240.7339-3-christian.koenig@amd.com
This commit is contained in:
Christian König 2021-07-20 15:37:35 +02:00
parent b83dcd753d
commit 044e55b146
1 changed files with 5 additions and 8 deletions
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13
drivers/dma-buf/dma-fence.c
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@ -616,20 +616,17 @@ EXPORT_SYMBOL(dma_fence_enable_sw_signaling);
* @cb: the callback to register
* @func: the function to call
*
* Add a software callback to the fence. The caller should keep a reference to
* the fence.
*
* @cb will be initialized by dma_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
* 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 dma_fence_wait(), however the caller doesn't need to
* keep a refcount to fence afterward dma_fence_add_callback() has returned:
* when software access is enabled, the creator of the fence is required to keep
* the fence alive until after it signals with dma_fence_signal(). The callback
* itself can be called from irq context.
* Note that the callback can be called from an atomic context or irq context.
*
* Returns 0 in case of success, -ENOENT if the fence is already signaled
* and -EINVAL in case of error.