From e7fc2756fd0d2276c4d239830f6a7204f1ee6808 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Christian=20K=C3=B6nig?= <christian.koenig@amd.com>
Date: Tue, 20 Jul 2021 15:37:35 +0200
Subject: dma-buf: clarify dma_fence_add_callback documentation
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Git-commit: 044e55b14657feb7522715ecec351990bd232ae0
Patch-mainline: v5.16-rc1
References: jsc#PED-1166 jsc#PED-1168 jsc#PED-1170 jsc#PED-1218 jsc#PED-1220 jsc#PED-1222 jsc#PED-1223 jsc#PED-1225

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
Acked-by: Patrik Jakobsson <pjakobsson@suse.de>
---
 drivers/dma-buf/dma-fence.c | 13 +++++--------
 1 file changed, 5 insertions(+), 8 deletions(-)

diff --git a/drivers/dma-buf/dma-fence.c b/drivers/dma-buf/dma-fence.c
index ce0f5eff575d..1e82ecd443fa 100644
--- a/drivers/dma-buf/dma-fence.c
+++ b/drivers/dma-buf/dma-fence.c
@@ -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.
-- 
2.38.1