[PATCH] drm: rcar-du: Replace drm_driver GEM ops with GEM object functions

[Noralf Trønnes]

Den 18.06.2019 18.35, skrev Laurent Pinchart:
> Hi Noralf,
> 
> On Tue, Jun 18, 2019 at 03:56:19PM +0200, Noralf Trønnes wrote:
>> Den 18.06.2019 15.13, skrev Laurent Pinchart:
>>> The recommended way to specify GEM object functions is to provide a
>>> drm_gem_object_funcs structure instance and set the GEM object to point
>>> to it. The drm_cma_gem_create_object_default_funcs() function provided
>>> by the GEM CMA helper does so when creating the GEM object, simplifying
>>> the driver implementation. Switch to it, and remove the then unneeded
>>> GEM-related opertions from rcar_du_driver.
>>
>> s/opertions/operations/
> 
> Oops, will fix.
> 
>>> Suggested-by: Daniel Vetter <daniel.vetter at ffwll.ch>
>>> Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas at ideasonboard.com>
>>> ---
>>>  drivers/gpu/drm/rcar-du/rcar_du_drv.c | 8 +-------
>>>  1 file changed, 1 insertion(+), 7 deletions(-)
>>>
>>> Daniel, is this what you had in mind ?
>>>
>>> diff --git a/drivers/gpu/drm/rcar-du/rcar_du_drv.c b/drivers/gpu/drm/rcar-du/rcar_du_drv.c
>>> index 3e5e835ea2b6..4cbb82009931 100644
>>> --- a/drivers/gpu/drm/rcar-du/rcar_du_drv.c
>>> +++ b/drivers/gpu/drm/rcar-du/rcar_du_drv.c
>>> @@ -445,16 +445,10 @@ DEFINE_DRM_GEM_CMA_FOPS(rcar_du_fops);
>>>  static struct drm_driver rcar_du_driver = {
>>>  	.driver_features	= DRIVER_GEM | DRIVER_MODESET | DRIVER_PRIME
>>>  				| DRIVER_ATOMIC,
>>> -	.gem_free_object_unlocked = drm_gem_cma_free_object,
>>> -	.gem_vm_ops		= &drm_gem_cma_vm_ops,
>>> +	.gem_create_object      = drm_cma_gem_create_object_default_funcs,
>>>  	.prime_handle_to_fd	= drm_gem_prime_handle_to_fd,
>>>  	.prime_fd_to_handle	= drm_gem_prime_fd_to_handle,
>>> -	.gem_prime_import	= drm_gem_prime_import,
>>> -	.gem_prime_export	= drm_gem_prime_export,
>>> -	.gem_prime_get_sg_table	= drm_gem_cma_prime_get_sg_table,
>>>  	.gem_prime_import_sg_table = drm_gem_cma_prime_import_sg_table,
>>> -	.gem_prime_vmap		= drm_gem_cma_prime_vmap,
>>> -	.gem_prime_vunmap	= drm_gem_cma_prime_vunmap,
>>>  	.gem_prime_mmap		= drm_gem_cma_prime_mmap,
>>
>> If you want to pick up yet another recommendation, you can use
>> drm_gem_prime_mmap here.
> 
> I compared the two call stacks and they appear similar, even if
> drm_gem_prime_mmap() leads to a more convoluted code flow. For my
> information, what's the advantage in using it ?

It's part of Daniels quest to remove the drm_driver gem callbacks. AFAIU
drm_gem_prime_mmap() is a stop gap on the way to remove
drm_driver.gem_prime_mmap. I saw it documented in his recent series:
[03/59] drm/prime: Update docs
https://patchwork.freedesktop.org/patch/310608/

+/**
+ * drm_gem_dmabuf_mmap - dma_buf mmap implementation for GEM
+ * @dma_buf: buffer to be mapped
+ * @vma: virtual address range
+ *
+ * Provides memory mapping for the buffer. This can be used as the
+ * &dma_buf_ops.mmap callback. It just forwards to
&drm_driver.gem_prime_mmap,
+ * which should be set to drm_gem_prime_mmap().
+ *
+ * FIXME: There's really no point to this wrapper, drivers which need
anything
+ * else but drm_gem_prime_mmap can roll their own &dma_buf_ops.mmap
callback.
+ *
+ * Returns 0 on success or a negative error code on failure.
+ */

Noralf.

> 
>> Either way:
>>
>> Reviewed-by: Noralf Trønnes <noralf at tronnes.org>
>>
>>>  	.dumb_create		= rcar_du_dumb_create,
>>>  	.fops			= &rcar_du_fops,
>