[PATCH v3 0/7] vt: Simplify console-blanking interface

[Thomas Zimmermann]

Update con_blank from struct consw to use enum vesa_blank_mode according
to its intended semantics. Handle unblanking in the separate new callback
con_unblank. Update all consoles.

Some background: the vt subsystem calls con_blank with what at first
appears to be nonsensical arguments: the blank value and the type of the
blank parameter do not match. con_blank mixes up console blank state and
monitor DPMS levels for power saving in the same argument. The
implementation of con_blank in various consoles suffers from a similar
problem: their interpretation of the given blank value often disagrees
with what the value's type suggests.

Patch 1 adds a new helper con_unblank, which handles all unblanking. This
allows for changing con_blank to only handle blanking. There's support
for both semantics while consoles are being converted.

Patches 2 to 6 implement con_unblank for the individual consoles. With
this, con_blank changes to its new semantics. Each console gets a single
callback for blanking and a single callback for unblanking.

With all consoles updated, patch 7 removes the old semantics and the
mode_switch parameter.

Tested with vgacon on a SiS 6202 VGA and with fbcon on a Matrox G200
VGA device. The latter also ran fbcon via DRM fbdev emulation. It's easy
to test this with setterm, like this:

  setterm --blank force          # blank
  setterm --blank poke           # unblank
  setterm --powersave powerdown  # set VESA DPMS level 3
  setterm --blank force          # blank and turn off monitor
  setterm --blank poke           # unblank

Blanking and unblanking still works in all tested cases.

Newport and sticon are built-only, due to a lack of test equipment.

Future directions: console blanking helper currently handle switching a
console between text and graphics mode. The mode_switch parameter indicates
this to the console. As suggested in earlier reviews, a later series might
rework the mode switching entirely.

v3:
- avoid possible regressions by adding back mode_switch
v2:
- rewrite series with con_unblank (GregKH)
- drop mode_switch from console implementations

Thomas Zimmermann (7):
  vt: Add con_unblank callback to struct consw
  dummycon: Implement struct consw.con_unblank
  fbcon: Implement struct consw.con_unblank
  newport_con: Implement struct consw.con_unblank
  sticon: Implement struct consw.con_unblank
  vgacon: Implement struct consw.con_unblank
  vt: Remove old-style con_blank

 drivers/tty/vt/vt.c                 | 11 +++---
 drivers/video/console/dummycon.c    | 12 +++++++
 drivers/video/console/newport_con.c | 24 +++++++------
 drivers/video/console/sticon.c      | 20 ++++++-----
 drivers/video/console/vgacon.c      | 46 +++++++++++++-----------
 drivers/video/fbdev/core/fbcon.c    | 55 ++++++++++++++++++++---------
 include/linux/console.h             | 10 ++++--
 7 files changed, 114 insertions(+), 64 deletions(-)


base-commit: 5b9ee97c47574138633a1cb70a32d118b6860a43
-- 
2.56.0