Re: [PATCH v2 6/7] drm/vkms: add reflect-y property

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Fri, Apr 14, 2023 at 02:53:55PM -0300, Maíra Canal wrote:
> On 4/14/23 11:46, Ville Syrjälä wrote:
> > On Fri, Apr 14, 2023 at 11:37:17AM -0300, Maíra Canal wrote:
> >> On 4/14/23 11:24, Ville Syrjälä wrote:
> >>> On Fri, Apr 14, 2023 at 10:51:50AM -0300, Maíra Canal wrote:
> >>>> Currently, vkms only support the reflect-x property. Therefore, add the
> >>>> reflect-y property to vkms through a software implementation of the
> >>>> operation. This is possible by reverse reading the y axis during the
> >>>> blending.
> >>>>
> >>>> Now, vkms support all possible rotation values.
> >>>>
> >>>> Tested with igt@kms_rotation_crc@primary-reflect-y and
> >>>> igt@kms_rotation_crc@sprite-reflect-y [1].
> >>>>
> >>>> [1] https://patchwork.freedesktop.org/series/116025/
> >>>>
> >>>> Signed-off-by: Maíra Canal <mcanal@igalia.com>
> >>>> ---
> >>>>    drivers/gpu/drm/vkms/vkms_composer.c |  7 ++++++-
> >>>>    drivers/gpu/drm/vkms/vkms_plane.c    | 16 ++++------------
> >>>>    2 files changed, 10 insertions(+), 13 deletions(-)
> >>>>
> >>>> diff --git a/drivers/gpu/drm/vkms/vkms_composer.c b/drivers/gpu/drm/vkms/vkms_composer.c
> >>>> index b05bd008aeab..19d1078e9d34 100644
> >>>> --- a/drivers/gpu/drm/vkms/vkms_composer.c
> >>>> +++ b/drivers/gpu/drm/vkms/vkms_composer.c
> >>>> @@ -92,8 +92,13 @@ static int get_y_pos(struct vkms_frame_info *frame_info, int y)
> >>>>    			return -1;
> >>>>    		return y + frame_info->dst.x1;
> >>>>    	default:
> >>>> -		return y;
> >>>> +		break;
> >>>>    	}
> >>>> +
> >>>> +	if (frame_info->rotation & DRM_MODE_REFLECT_Y)
> >>>> +		return drm_rect_height(&frame_info->dst) - y - 1;
> >>>> +
> >>>> +	return y;
> >>>>    }
> >>>>    
> >>>>    static bool check_limit(struct vkms_frame_info *frame_info, int pos)
> >>>> diff --git a/drivers/gpu/drm/vkms/vkms_plane.c b/drivers/gpu/drm/vkms/vkms_plane.c
> >>>> index 11662afa9fe4..d08bda869a24 100644
> >>>> --- a/drivers/gpu/drm/vkms/vkms_plane.c
> >>>> +++ b/drivers/gpu/drm/vkms/vkms_plane.c
> >>>> @@ -121,12 +121,8 @@ static void vkms_plane_atomic_update(struct drm_plane *plane,
> >>>>    	frame_info->fb = fb;
> >>>>    	memcpy(&frame_info->map, &shadow_plane_state->data, sizeof(frame_info->map));
> >>>>    	drm_framebuffer_get(frame_info->fb);
> >>>> -	frame_info->rotation = drm_rotation_simplify(new_state->rotation,
> >>>> -						     DRM_MODE_ROTATE_0 |
> >>>> -						     DRM_MODE_ROTATE_90 |
> >>>> -						     DRM_MODE_ROTATE_180 |
> >>>> -						     DRM_MODE_ROTATE_270 |
> >>>> -						     DRM_MODE_REFLECT_X);
> >>>> +	frame_info->rotation = drm_rotation_simplify(new_state->rotation, DRM_MODE_ROTATE_MASK |
> >>>> +						     DRM_MODE_REFLECT_MASK);
> >>>
> >>> What are you trying to achieve with that?
> >>
> >> Yeah, seeing it right now I can see that this is not achieving anything.
> >> I will remove it in the next version.
> > 
> > I think using it might still make sense to eg. remove the 180/270
> > cases from your actual rendering code.
> 
> I will remove it on the next version.
> 
> > 
> > I'm also a bit uneasy about all that hand rolled coordinate calculation
> > stuff. Ideally drm_rect_rotate*() should handle all that for you, and
> > make sure the rotate vs. reflect actually get applied in the correct
> > order.
> > 
> 
> At first, I had a similar idea that drm_rect_rotate() would handle all the
> rotation. But, this turn out to be untrue. From what I can see, although
> the drm_rect_rotate() helps by performing the coordinates rotation, we also
> need to change the way the blending occurs. Although the coordinates have
> changed, the vmap stays the same and we will still start reading the vmap
> by the first line (y = 0). That's why we need to change the iteration
> boundaries in the blending loops.
> 
> So, drm_rect_rotate() is a part of the solution, but it is not able to handle
> it completely.
> 
> If you have any suggestions on how to perform the rotation without changing
> the way the blending occurs, I would be glad to hear. Unfortunately, just
> performing drm_rect_rotate() doesn't seem to be a solution.

Dunno how vkms does this currently, but the most straightforward
solution I can think of would be something like this:

struct drm_rect src;

drm_rect_fp_to_int(&src, plane_state->src);

drm_rect_rotate(&src, fb->width, fb->height, rotation);

for (dy = dst->y1; dy < dst->y2; dy++) {
	for (dx = dst->x1; dx < dst->x2; dx++) {
		int _sx = dx - dst->x1 + src.x1;
		int _sy = dy - dst->y1 + src.y1;
		struct drm_rect s;

		drm_rect_init(&s, _sx, _sy, 1, 1);

		drm_rect_rotate_inv(&s, fb->width, fb->height, rotation);

		output_pixel(dx, dy, s.x1, s.y1);
	}
}

-- 
Ville Syrjälä
Intel