forked from luck/tmp_suning_uos_patched
460f6b1a23
commit 87ab9f6b7417349aa197a6c7098d4fdd4beebb74 upstream.
This reverts commit 39aead8373b3c20bb5965c024dfb51a94e526151.
Revert the first (of 2) commits which disabled scrolling acceleration in
fbcon/fbdev. It introduced a regression for fbdev-supported graphic cards
because of the performance penalty by doing screen scrolling by software
instead of using the existing graphic card 2D hardware acceleration.
Console scrolling acceleration was disabled by dropping code which
checked at runtime the driver hardware capabilities for the
BINFO_HWACCEL_COPYAREA or FBINFO_HWACCEL_FILLRECT flags and if set, it
enabled scrollmode SCROLL_MOVE which uses hardware acceleration to move
screen contents. After dropping those checks scrollmode was hard-wired
to SCROLL_REDRAW instead, which forces all graphic cards to redraw every
character at the new screen position when scrolling.
This change effectively disabled all hardware-based scrolling acceleration for
ALL drivers, because now all kind of 2D hardware acceleration (bitblt,
fillrect) in the drivers isn't used any longer.
The original commit message mentions that only 3 DRM drivers (nouveau, omapdrm
and gma500) used hardware acceleration in the past and thus code for checking
and using scrolling acceleration is obsolete.
This statement is NOT TRUE, because beside the DRM drivers there are around 35
other fbdev drivers which depend on fbdev/fbcon and still provide hardware
acceleration for fbdev/fbcon.
The original commit message also states that syzbot found lots of bugs in fbcon
and thus it's "often the solution to just delete code and remove features".
This is true, and the bugs - which actually affected all users of fbcon,
including DRM - were fixed, or code was dropped like e.g. the support for
software scrollback in vgacon (commit
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|---|---|---|
| .. | ||
| bridge | ||
| dp-mst | ||
| afbc.rst | ||
| amdgpu-dc.rst | ||
| amdgpu.rst | ||
| backlight.rst | ||
| drivers.rst | ||
| drm-client.rst | ||
| drm-internals.rst | ||
| drm-kms-helpers.rst | ||
| drm-kms.rst | ||
| drm-mm.rst | ||
| drm-uapi.rst | ||
| i915.rst | ||
| index.rst | ||
| introduction.rst | ||
| kms-properties.csv | ||
| komeda-kms.rst | ||
| mcde.rst | ||
| meson.rst | ||
| msm-crash-dump.rst | ||
| pl111.rst | ||
| tegra.rst | ||
| todo.rst | ||
| tve200.rst | ||
| v3d.rst | ||
| vc4.rst | ||
| vga-switcheroo.rst | ||
| vgaarbiter.rst | ||
| vkms.rst | ||
| xen-front.rst | ||