[PATCH 1/2] drm/fb_cma_helper: Add drm_fb_cma_setup_fence() helper

[Marek Vasut]

On 09/29/2016 11:36 AM, Daniel Vetter wrote:
> On Wed, Sep 28, 2016 at 10:08:21PM +0200, Marek Vasut wrote:
>> On 09/28/2016 03:55 PM, Lucas Stach wrote:
>>> Hi Marek,
>>>
>>> Am Montag, den 26.09.2016, 15:01 +0200 schrieb Marek Vasut:
>>>> Add new drm_fb_cma_setup_fence() helper function extracted from the
>>>> imx-drm driver. This function checks if the plane has DMABUF attached
>>>> to it and if so, sets up the fence on which the atomic helper can wait.
>>>>
>>>> Signed-off-by: Marek Vasut <marex at denx.de>
>>>> Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
>>>> Cc: Lucas Stach <l.stach at pengutronix.de>
>>>> ---
>>>>  drivers/gpu/drm/drm_fb_cma_helper.c | 26 ++++++++++++++++++++++++++
>>>>  include/drm/drm_fb_cma_helper.h     |  3 +++
>>>>  2 files changed, 29 insertions(+)
>>>>
>>>> diff --git a/drivers/gpu/drm/drm_fb_cma_helper.c b/drivers/gpu/drm/drm_fb_cma_helper.c
>>>> index 1fd6eac..2441707 100644
>>>> --- a/drivers/gpu/drm/drm_fb_cma_helper.c
>>>> +++ b/drivers/gpu/drm/drm_fb_cma_helper.c
>>>> @@ -23,8 +23,10 @@
>>>>  #include <drm/drm_crtc_helper.h>
>>>>  #include <drm/drm_gem_cma_helper.h>
>>>>  #include <drm/drm_fb_cma_helper.h>
>>>> +#include <linux/dma-buf.h>
>>>>  #include <linux/dma-mapping.h>
>>>>  #include <linux/module.h>
>>>> +#include <linux/reservation.h>
>>>>  
>>>>  #define DEFAULT_FBDEFIO_DELAY_MS 50
>>>>  
>>>> @@ -265,6 +267,30 @@ struct drm_gem_cma_object *drm_fb_cma_get_gem_obj(struct drm_framebuffer *fb,
>>>>  }
>>>>  EXPORT_SYMBOL_GPL(drm_fb_cma_get_gem_obj);
>>>>  
>>>> +/**
>>>> + * drm_fb_cma_setup_fence() - Set up the fence for atomic helper to wait on
>>>
>>> I don't really like the naming of the helper. It's not setting up any
>>> fence, it's either extracting it from the plane and/or attaching it to
>>> the planestate, so I would have expected the name to include extract or
>>> attach.
> 
> Imo for helpers that should be put into a specific vhook like this here,
> it'd go with that vhooks name. So here drm_fb_cma_prepare_fb.

I have the following right now, I think that's more descriptive as this
function is not preparing the FB in any way.

/**
 * drm_fb_cma_extract_and_attach_fence() - Extract fence from plane and
attach to planestate
 * @plane: Which plane
 * @state: Plane state attach fence to
 *
 * If the plane fb has an dma-buf attached, fish out the exclusive
 * fence and attach it to plane state for the atomic helper to wait
 * on.
 */

> And then in the kerneldoc also mention where it should be put (both for
> drivers using atomic helpers, and those using simple pipe helpers), e.g.
> "This should be put into the prepare_fb hook of struct
> &drm_plane_helper_funcs."
> 
> Please run $ make htmldocs to make sure the docs look pretty and the
> generated links are correct.
> -Daniel
> 
>>>
>>>> + * @plane: Which plane
>>>> + * @state: Plane state to check
>>>
>>> s/check/attach fence to
>>
>> Both fixed in V2, thanks.
>>
>>>> + *
>>>> + * If the plane fb has an dma-buf attached, fish out the exclusive
>>>> + * fence for the atomic helper to wait on.
>>>> + */
>>>> +void drm_fb_cma_setup_fence(struct drm_plane *plane,
>>>> +			    struct drm_plane_state *state)
>>>> +{
>>>> +	struct dma_buf *dma_buf;
>>>> +
>>>> +	if ((plane->state->fb == state->fb) || !state->fb)
>>>> +		return;
>>>> +
>>>> +	dma_buf = drm_fb_cma_get_gem_obj(state->fb, 0)->base.dma_buf;
>>>> +	if (!dma_buf)
>>>> +		return;
>>>> +
>>>> +	state->fence = reservation_object_get_excl_rcu(dma_buf->resv);
>>>> +}
>>>> +EXPORT_SYMBOL_GPL(drm_fb_cma_setup_fence);
>>>> +
>>>>  #ifdef CONFIG_DEBUG_FS
>>>>  static void drm_fb_cma_describe(struct drm_framebuffer *fb, struct seq_file *m)
>>>>  {
>>>> diff --git a/include/drm/drm_fb_cma_helper.h b/include/drm/drm_fb_cma_helper.h
>>>> index f313211..fc122d3 100644
>>>> --- a/include/drm/drm_fb_cma_helper.h
>>>> +++ b/include/drm/drm_fb_cma_helper.h
>>>> @@ -41,6 +41,9 @@ struct drm_framebuffer *drm_fb_cma_create(struct drm_device *dev,
>>>>  struct drm_gem_cma_object *drm_fb_cma_get_gem_obj(struct drm_framebuffer *fb,
>>>>  	unsigned int plane);
>>>>  
>>>> +void drm_fb_cma_setup_fence(struct drm_plane *plane,
>>>> +			    struct drm_plane_state *state);
>>>> +
>>>>  #ifdef CONFIG_DEBUG_FS
>>>>  struct seq_file;
>>>>  
>>>
>>>
>>
>>
>> -- 
>> Best regards,
>> Marek Vasut
> 


-- 
Best regards,
Marek Vasut