[PATCH 3/5] drm/syncobj: add sync_file interaction.

[Dave Airlie]

On 4 August 2017 at 02:25, Chris Wilson <chris at chris-wilson.co.uk> wrote:
> Quoting Dave Airlie (2017-05-12 01:34:55)
>> @@ -385,6 +434,13 @@ drm_syncobj_fd_to_handle_ioctl(struct drm_device *dev, void *data,
>>         if (!drm_core_check_feature(dev, DRIVER_SYNCOBJ))
>>                 return -ENODEV;
>>
>> +       if (args->flags & DRM_SYNCOBJ_FD_TO_HANDLE_FLAGS_IMPORT_SYNC_FILE_FENCE)
>> +               return drm_syncobj_import_sync_file_fence(file_private,
>> +                                                         args->fd,
>> +                                                         args->handle);
>> +       else if (args->flags)
>> +               return -EINVAL;
>
> Argh, what I missed before was that importing from a sync_file reuses
> the handle, but importing from a syncobj fd creates a new handle.
>
> Just venting my ocd. It would be nice if the interface was consistent,
> and I can see arguments for both approaches (just not a good argument as
> to why they should differ). A compromise would be a flag to create/reuse
> handle (or if handle=0, create, if handle!=0 resuse).

The interface is consistent for the objects.

With a sync_fd import you import the state into an existing syncobj.

With a syncobj import you import the object into the current process state
(so get a new handle).

I can't think of a use case for anything else, maybe having a sync_fd state
imported into a new syncobj? but not sure it really helps.

Userspace should be using different paths to get to these interfaces.

Dave.