[Letux-kernel] framebuffer rotation
H. Nikolaus Schaller
hns at goldelico.com
Mon Sep 9 10:47:54 CEST 2019
> Am 09.09.2019 um 10:40 schrieb Michael Mrozek <EvilDragon at openpandora.org>:
> Isn't that a simple software rotation?
I have no idea what the differences are... That is why I am asking :)
> If it is, it should be really slow.
Well, it may be a rotation feature of the text console driver. Some indication
is that there is no "drm" in the /sys/class path.
For a console I would think speed does not matter much. But it may or may
not use hardware rotation.
Looks as if we need someone who can explain the full software architecture in detail,
i.e. every single step from user-space to display pixel and where which driver
component is relevant...
> On 9 September 2019 10:18:26 CEST, "H. Nikolaus Schaller" <hns at goldelico.com> wrote:
> I just learned that
> root at letux:~# echo 0 > /sys/class/graphics/fbcon/rotate_all
> root at letux:~# echo 1 > /sys/class/graphics/fbcon/rotate_all
> root at letux:~# echo 2 > /sys/class/graphics/fbcon/rotate_all
> root at letux:~# echo 3 > /sys/class/graphics/fbcon/rotate_all
> also does screen/framebuffer rotation.
> Now I wonder why we need to patch drm_fb_helper (which is
> currently broken in letux-5.3) and have our own ./tiler-ctl
> Any suggestions or explanations are welcome.
> BR and thanks,
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> Michael Mrozek
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