[PATCH] drm: Return error codes from struct drm_driver.gem_create_object

[Dan Carpenter]

On Tue, Nov 30, 2021 at 10:52:55AM +0100, Thomas Zimmermann wrote:
> GEM helper libraries use struct drm_driver.gem_create_object to let
> drivers override GEM object allocation. On failure, the call returns
> NULL.
> 
> Change the semantics to make the calls return a pointer-encoded error.
> This aligns the callback with its callers. Fixes the ingenic driver,
> which already returns an error pointer.
> 
> Also update the callers to handle the involved types more strictly.
> 
> Signed-off-by: Thomas Zimmermann <tzimmermann at suse.de>
> ---
> There is an alternative patch at [1] that updates the value returned
> by ingenics' gem_create_object to NULL. Fixing the interface to return
> an errno code is more consistent with the rest of the GEM functions.
> 
> [1] https://lore.kernel.org/dri-devel/20211118111522.GD1147@kili/ 

My fix was already applied and backported to -stable etc...  Your
patch is not developed against a current tree so you broke it.

That's the tricky thing with changing the API because say people wrote
their code last week where returning NULL was correct.  When they submit
their driver upstream, everything will merge and build but it will break
at runtime.

For now, it's only vc4_create_object() which is broken.

regards,
dan carpenter