Re: [RFC 02/12] staging/android/sync: add sync_fence_create_dma

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

On 23/11/15 13:38, John Harrison wrote:
> On 23/11/2015 13:27, Maarten Lankhorst wrote:
>> Op 23-11-15 om 12:34 schreef John.C.Harrison@Intel.com:
>>> From: Maarten Lankhorst <maarten.lankhorst@canonical.com>
>>>
>>> This allows users of dma fences to create a android fence.
>>>
>>> v2: Added kerneldoc. (Tvrtko Ursulin).
>>>
>>> Signed-off-by: Maarten Lankhorst <maarten.lankhorst@canonical.com>
>>> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
>>> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
>>> Cc: Daniel Vetter <daniel@ffwll.ch>
>>> Cc: Jesse Barnes <jbarnes@virtuousgeek.org>
>>> Cc: devel@driverdev.osuosl.org
>>> Cc: Riley Andrews <riandrews@android.com>
>>> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>>> Cc: Arve Hjønnevåg <arve@android.com>
>>> ---
>>>   drivers/staging/android/sync.c | 13 +++++++++----
>>>   drivers/staging/android/sync.h | 12 +++++++++++-
>>>   2 files changed, 20 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/drivers/staging/android/sync.c
>>> b/drivers/staging/android/sync.c
>>> index f83e00c..7f0e919 100644
>>> --- a/drivers/staging/android/sync.c
>>> +++ b/drivers/staging/android/sync.c
>>> @@ -188,7 +188,7 @@ static void fence_check_cb_func(struct fence *f,
>>> struct fence_cb *cb)
>>>   }
>>>   /* TODO: implement a create which takes more that one sync_pt */
>>> -struct sync_fence *sync_fence_create(const char *name, struct
>>> sync_pt *pt)
>>> +struct sync_fence *sync_fence_create_dma(const char *name, struct
>>> fence *pt)
>>>   {
>>>       struct sync_fence *fence;
>>> @@ -199,16 +199,21 @@ struct sync_fence *sync_fence_create(const char
>>> *name, struct sync_pt *pt)
>>>       fence->num_fences = 1;
>>>       atomic_set(&fence->status, 1);
>>> -    fence->cbs[0].sync_pt = &pt->base;
>>> +    fence->cbs[0].sync_pt = pt;
>>>       fence->cbs[0].fence = fence;
>>> -    if (fence_add_callback(&pt->base, &fence->cbs[0].cb,
>>> -                   fence_check_cb_func))
>>> +    if (fence_add_callback(pt, &fence->cbs[0].cb, fence_check_cb_func))
>>>           atomic_dec(&fence->status);
>>>       sync_fence_debug_add(fence);
>>>       return fence;
>>>   }
>>> +EXPORT_SYMBOL(sync_fence_create_dma);
>>> +
>>> +struct sync_fence *sync_fence_create(const char *name, struct
>>> sync_pt *pt)
>>> +{
>>> +    return sync_fence_create_dma(name, &pt->base);
>>> +}
>>>   EXPORT_SYMBOL(sync_fence_create);
>>>   struct sync_fence *sync_fence_fdget(int fd)
>>> diff --git a/drivers/staging/android/sync.h
>>> b/drivers/staging/android/sync.h
>>> index 61f8a3a..798cd56 100644
>>> --- a/drivers/staging/android/sync.h
>>> +++ b/drivers/staging/android/sync.h
>>> @@ -250,10 +250,20 @@ void sync_pt_free(struct sync_pt *pt);
>>>    * @pt:        sync_pt to add to the fence
>>>    *
>>>    * Creates a fence containg @pt.  Once this is called, the fence takes
>>> - * ownership of @pt.
>>> + * a reference on @pt.
>>>    */
>>>   struct sync_fence *sync_fence_create(const char *name, struct
>>> sync_pt *pt);
>> No it doesn't.
>>> +/**
>>> + * sync_fence_create_dma() - creates a sync fence from dma-fence
>>> + * @name:    name of fence to create
>>> + * @pt:    dma-fence to add to the fence
>>> + *
>>> + * Creates a fence containg @pt.  Once this is called, the fence takes
>>> + * a reference on @pt.
>>> + */
>> No it doesn't.
> This is your patch isn't it? Or is this something Tvrtko added on the
> way past? Either way, what should the correct description be? It takes a

It is Maarten's patch, I just copied the comment over from one function 
to another. The one I picked up was 
https://patchwork.freedesktop.org/patch/38074/, December 2014.

> copy of the pointer to 'pt'. Is the comment meaning a reference in the
> sense of 'pass by reference', i.e. a pointer? But you are meaning a
> reference in the sense of incrementing a usage count?

Maybe he means it is still taking ownership, not reference?

Regards,

Tvrtko
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