On 2019-01-10 21:16, Sam Ravnborg wrote:

Hi Peter.

(Hijacking this thread as I lost the orginal mails)

Assuming you wanted to reply to this patch?
https://patchwork.kernel.org/patch/10753571/

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I found an unfortunate issue while recoding plane handling to use
drm_atomic_helper_check_plane_state(). The driver rotates clockwise,
which is not correct. I simply fixed it (patch 1/4), but maybe that
will cause regressions for unsuspecting users who simply assumed
that the clockwise rotation was correct? I don't know what to do
about that? Adding an option to get the old broken behavior seems
useless, wouldn't it be just as easy to just fix whatever app to
rotate the other way instead of adding an option somewhere?

Hm, rotation support has been added before the standard rotation
property was created, and at that time I assumed rotation was clockwise
(which apparently was an unwise choice). Anyway, I don't have a
solution for this problem, so I'll let Nicolas decide if it's
acceptable to change the rotation behavior.

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I have only tested this series on sama5d3, but I did check the docs
for various other chips (sama5d2, sama5d4, sam9n12, sam9g15, sam9g35
and sam9x35) supported by the driver (relevant to patch 4/4).

I wonder if, when this code path is anyway touched, could benefit
from drm_rect_rotate().

It is obviously not a simple replacement, but could it be used then
I hope the resulting code is simpler.

What are you referring to that goes beyond what is done in patch 3/4
in this series? After setting up the strides, the only use of src_[xywh]
are to calculate the scaling factors, and for that the position is
irrelevant. I.e. src_x and src_y are not used. Sure, in some theoretical
sense it might be good if src_[xy] are also transformed into the rotated
coordinate system along with src_[wh], but it seems a bit backwards to
switch over to struct drm_rect when the interesting properties are the
width and height, not the coordinates of the corners. No strong feelings
on the issue though...

Cheers,
Peter
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