Hi, On Mon, Dec 09, 2019 at 07:32:54PM +0100, Stephan Gerhold wrote: > At the moment, video mode parameters like video=540x960,reflect_x, > (without rotation set) are silently ignored. > > One of the reasons for this is that the calculation that > combines the panel_orientation with cmdline->rotation_reflection > does not handle the case when cmdline->rotation_reflection does > not have any rotation set. > (i.e. cmdline->rotation_reflection & DRM_MODE_ROTATE_MASK == 0) > > Example: > *rotation = DRM_MODE_ROTATE_0 (no panel_orientation) > cmdline->rotation_reflection = DRM_MODE_REFLECT_X (video=MODE,reflect_x) > > The current code does: > panel_rot = ilog2(*rotation & DRM_MODE_ROTATE_MASK); > cmdline_rot = ilog2(cmdline->rotation_reflection & DRM_MODE_ROTATE_MASK); > sum_rot = (panel_rot + cmdline_rot) % 4; > > and therefore: > panel_rot = ilog2(DRM_MODE_ROTATE_0) = ilog2(1) = 0 > cmdline_rot = ilog2(0) = -1 > sum_rot = (0 + -1) % 4 = -1 % 4 = 3 > ... > *rotation = DRM_MODE_ROTATE_270 | DRM_MODE_REFLECT_X > > So we incorrectly generate DRM_MODE_ROTATE_270 in this case. > To prevent cmdline_rot from becoming -1, we need to treat > the rotation as DRM_MODE_ROTATE_0. > > On the other hand, there is no need to go through that calculation > at all if no rotation is set in rotation_reflection. > A simple XOR is enough to combine the reflections. > > Finally, also allow DRM_MODE_ROTATE_0 in the if statement below. > DRM_MODE_ROTATE_0 means "no rotation" and should therefore not > require any special handling (e.g. specific tiling format). > > This makes video parameters with only reflect option work correctly. > > Signed-off-by: Stephan Gerhold <stephan@xxxxxxxxxxx> Thanks for that commit message. Can you also add a selftest to make sure we don't get a regression in the future? Thanks! Maxime
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