[PATCH v2 0/7] vt: Simplify console-blanking interface

[Thomas Zimmermann]

Update con_blank from struct consw to use enum vesa_blank_mode according
to its intented 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 non-sensical value. This is because 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. Switching a
console between text and graphics mode is currently tied to the blanking
helpers. The mode_switch parameter controls this. As suggested in the
earlier reviews, rather detect a mode switch from the existing state.
The mode_switch parameter is deprecated. A later series might rework the
mode switching entirely.

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.

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                 |  9 ++---
 drivers/video/console/dummycon.c    | 18 +++++++--
 drivers/video/console/newport_con.c | 27 ++++++-------
 drivers/video/console/sticon.c      | 27 ++++++++-----
 drivers/video/console/vgacon.c      | 60 +++++++++++++++++------------
 drivers/video/fbdev/core/fbcon.c    | 60 ++++++++++++++++++++---------
 include/linux/console.h             | 12 +++---
 7 files changed, 132 insertions(+), 81 deletions(-)


base-commit: b0bd9fb9e92aae2a653efa1d0407daa2aabe99d0
-- 
2.55.0