[PATCH] drm/gem: Document that handle_create must be the last step

[Oleksandr Andrushchenko]

On 03/22/2018 10:02 AM, Daniel Vetter wrote:
> It published
s/It/If
>   the gem object to userspace, by that point other threads
> can guess the id and start using it. And gem IDs are _very_ easy to
> guess (it's just an idr).
>
> Since gem objects is the only thing we allow drivers to create
> themselves (all the kms/prime/syncobj stuff is handled by the core) no
> other functions seem to be in need of this clarification.
>
> Motivated by reviewing the xen-front kms driver.
>
> Cc: Oleksandr Andrushchenko <oleksandr_andrushchenko at epam.com>
> Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>
> ---
>   drivers/gpu/drm/drm_gem.c | 9 ++++++---
>   1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c
> index 4975ba9a7bc8..4a16d7b26c89 100644
> --- a/drivers/gpu/drm/drm_gem.c
> +++ b/drivers/gpu/drm/drm_gem.c
> @@ -436,9 +436,12 @@ drm_gem_handle_create_tail(struct drm_file *file_priv,
>    * @obj: object to register
>    * @handlep: pionter to return the created handle to the caller
>    *
> - * Create a handle for this object. This adds a handle reference
> - * to the object, which includes a regular reference count. Callers
> - * will likely want to dereference the object afterwards.
> + * Create a handle for this object. This adds a handle reference to the object,
> + * which includes a regular reference count. Callers will likely want to
> + * dereference the object afterwards.
> + *
> + * Since this publishes @obj to userspace it must be fully set up by this point,
> + * drivers must call this last in their buffer object creation callbacks.
>    */
>   int drm_gem_handle_create(struct drm_file *file_priv,
>   			  struct drm_gem_object *obj,

Reviewed-by: Oleksandr Andrushchenko <oleksandr_andrushchenko at epam.com>