Re: [RFC PATCH 2/3] drm/atomic-helper: add REQUIRE_MATCHING_FB flag

[Stefan Agner <stefan@agner.ch>]

On 2020-09-11 10:52, Daniel Vetter wrote:
> On Thu, Sep 10, 2020 at 11:24:24AM +0200, Stefan Agner wrote:
>> Add flag which checks that the framebuffer size matches the plane size
>> exactly. This is useful for display controller which can't handle
>> framebuffers other than the plane/CRTC size.
>>
>> Signed-off-by: Stefan Agner <stefan@agner.ch>
>> ---
>>  drivers/gpu/drm/drm_atomic_helper.c               | 7 +++++++
>>  drivers/gpu/drm/selftests/test-drm_plane_helper.c | 9 +++++++++
>>  include/drm/drm_atomic_helper.h                   | 1 +
>>  3 files changed, 17 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
>> index 755572a37f3f..8bc7f8c2e566 100644
>> --- a/drivers/gpu/drm/drm_atomic_helper.c
>> +++ b/drivers/gpu/drm/drm_atomic_helper.c
>> @@ -802,6 +802,7 @@ int drm_atomic_helper_check_plane_state(struct drm_plane_state *plane_state,
>>  	int hscale, vscale;
>>  	bool can_position = flags & DRM_PLANE_CAN_POSITION;
>>  	bool can_update_disabled = flags & DRM_PLANE_CAN_UPDATE_DISABLED;
>> +	bool require_matching_fb = flags & DRM_PLANE_REQUIRE_MATCHING_FB;
>>
>>  	WARN_ON(plane_state->crtc && plane_state->crtc != crtc_state->crtc);
>>
>> @@ -860,6 +861,12 @@ int drm_atomic_helper_check_plane_state(struct drm_plane_state *plane_state,
>>  		return -EINVAL;
>>  	}
>>
>> +	if (require_matching_fb && (drm_rect_width(src) != fb->width ||
>> +	    drm_rect_height(src) != fb->height)) {
>> +		DRM_DEBUG_KMS("Framebuffer size must match plane size.\n");
>> +		return -EINVAL;
>> +	}
> 
> I think you also want to check that the x,y src are at (0, 0).

Hm, I was thinking that is handled by CAN_POSITION, but that really is
all about src vs. dst in plane coordinates.

I guess at that point its almost nicer to create a drm_rect for fb and
use drm_rect_equals.

--
Stefan

> 
> Plus needs kerneldoc.
> 
> But aside from the details, I like.
> 
>> +
>>  	return 0;
>>  }
>>  EXPORT_SYMBOL(drm_atomic_helper_check_plane_state);
>> diff --git a/drivers/gpu/drm/selftests/test-drm_plane_helper.c b/drivers/gpu/drm/selftests/test-drm_plane_helper.c
>> index 01e95b2d572f..2c81bbef830e 100644
>> --- a/drivers/gpu/drm/selftests/test-drm_plane_helper.c
>> +++ b/drivers/gpu/drm/selftests/test-drm_plane_helper.c
>> @@ -139,6 +139,15 @@ int igt_check_plane_state(void *ignored)
>>  	FAIL_ON(!check_src_eq(&plane_state, 0, 0, 1023 << 16, 767 << 16));
>>  	FAIL_ON(!check_crtc_eq(&plane_state, 0, 0, 1023, 767));
>>
>> +	/* Check whether requiring same size framebuffer works correctly. */
>> +	set_src(&plane_state, 0, 0, 1024 << 16, 768 << 16);
>> +	set_crtc(&plane_state, 0, 0, 1024, 768);
>> +	ret = drm_atomic_helper_check_plane_state(&plane_state, &crtc_state,
>> +						  DRM_PLANE_HELPER_NO_SCALING,
>> +						  DRM_PLANE_HELPER_NO_SCALING,
>> +						  DRM_PLANE_REQUIRE_MATCHING_FB);
>> +	FAIL(!ret, "Should not be able to use different size framebuffer with REQUIRE_MATCHING_FB\n");
> 
> I think also needs a negative test with src_x/y != 0, plus maybe one that
> succeeds.
> 
> Cheers, Daniel
>> +
>>  	/* Simple scaling tests. */
>>  	set_src(&plane_state, 0, 0, 512 << 16, 384 << 16);
>>  	set_crtc(&plane_state, 0, 0, 1024, 768);
>> diff --git a/include/drm/drm_atomic_helper.h b/include/drm/drm_atomic_helper.h
>> index bb9957b4f91b..244b730e84d3 100644
>> --- a/include/drm/drm_atomic_helper.h
>> +++ b/include/drm/drm_atomic_helper.h
>> @@ -43,6 +43,7 @@ int drm_atomic_helper_check_modeset(struct drm_device *dev,
>>
>>  #define DRM_PLANE_CAN_POSITION				BIT(0)
>>  #define DRM_PLANE_CAN_UPDATE_DISABLED			BIT(1)
>> +#define DRM_PLANE_REQUIRE_MATCHING_FB			BIT(2)
>>
>>  int drm_atomic_helper_check_plane_state(struct drm_plane_state *plane_state,
>>  					const struct drm_crtc_state *crtc_state,
>> --
>> 2.28.0
>>
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