Commit Graph

6 Commits

Author SHA1 Message Date
Hans de Goede
b0d8e409c3 video/console: Add dmi quirk table for x86 systems which need fbcon rotation
Some x86 clamshell design devices use portrait tablet screens and a
display engine which cannot rotate in hardware, so we need to rotate
the fbcon to compensate.

This commit adds a DMI based quirk table which is initially populated with
4 such devices: The Asus T100HA, GPD Pocket, the GPD win and the I.T.Works
TW891, so that the console comes up in the right orientation on these
devices OOTB.

Unfortunately these (cheap) devices also typically have quite generic DMI
data, so we match on a combination of DMI data, screen resolution and a
list of known BIOS dates to avoid false positives.

Suggested-by: Jean Delvare <jdelvare@suse.de>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Jean Delvare <jdelvare@suse.de>
[b.zolnierkie: ported over fbcon changes]
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
2017-08-18 19:56:39 +02:00
Daniel Vetter
6104c37094 fbcon: Make fbcon a built-time depency for fbdev
There's a bunch of folks who're trying to make printk less
contended and faster, but there's a problem: printk uses the
console_lock, and the console lock has become the BKL for all things
fbdev/fbcon, which in turn pulled in half the drm subsystem under that
lock. That's awkward.

There reasons for that is probably just a historical accident:

- fbcon is a runtime option of fbdev, i.e. at runtime you can pick
  whether your fbdev driver instances are used as kernel consoles.
  Unfortunately this wasn't implemented with some module option, but
  through some module loading magic: As long as you don't load
  fbcon.ko, there's no fbdev console support, but loading it (in any
  order wrt fbdev drivers) will create console instances for all fbdev
  drivers.

- This was implemented through a notifier chain. fbcon.ko enumerates
  all fbdev instances at load time and also registers itself as
  listener in the fbdev notifier. The fbdev core tries to register new
  fbdev instances with fbcon using the notifier.

- On top of that the modifier chain is also used at runtime by the
  fbdev subsystem to e.g. control backlights for panels.

- The problem is that the notifier puts a mutex locking context
  between fbdev and fbcon, which mixes up the locking contexts for
  both the runtime usage and the register time usage to notify fbcon.
  And at runtime fbcon (through the fbdev core) might call into the
  notifier from a printk critical section while console_lock is held.

- This means console_lock must be an outer lock for the entire fbdev
  subsystem, which also means it must be acquired when registering a
  new framebuffer driver as the outermost lock since we might call
  into fbcon (through the notifier) which would result in a locking
  inversion if fbcon would acquire the console_lock from its notifier
  callback (which it needs to register the console).

- console_lock can be held anywhere, since printk can be called
  anywhere, and through the above story, plus drm/kms being an fbdev
  driver, we pull in a shocking amount of locking hiercharchy
  underneath the console_lock. Which makes cleaning up printk really
  hard (not even splitting console_lock into an rwsem is all that
  useful due to this).

There's various ways to address this, but the cleanest would be to
make fbcon a compile-time option, where fbdev directly calls the fbcon
register functions from register_framebuffer, or dummy static inline
versions if fbcon is disabled. Maybe augmented with a runtime knob to
disable fbcon, if that's needed (for debugging perhaps).

But this could break some users who rely on the magic "loading
fbcon.ko enables/disables fbdev framebuffers at runtime" thing, even
if that's unlikely. Hence we must be careful:

1. Create a compile-time dependency between fbcon and fbdev in the
least minimal way. This is what this patch does.

2. Wait at least 1 year to give possible users time to scream about
how we broke their setup. Unlikely, since all distros make fbcon
compile-in, and embedded platforms only compile stuff they know they
need anyway. But still.

3. Convert the notifier to direct functions calls, with dummy static
inlines if fbcon is disabled. We'll still need the fb notifier for the
other uses (like backlights), but we can probably move it into the fb
core (atm it must be built-into vmlinux).

4. Push console_lock down the call-chain, until it is down in
console_register again.

5. Finally start to clean up and rework the printk/console locking.

For context of this saga see

commit 50e244cc79
Author: Alan Cox <alan@linux.intel.com>
Date:   Fri Jan 25 10:28:15 2013 +1000

    fb: rework locking to fix lock ordering on takeover

plus the pile of commits on top that tried to make this all work
without terminally upsetting lockdep. We've uncovered all this when
console_lock lockdep annotations where added in

commit daee779718
Author: Daniel Vetter <daniel.vetter@ffwll.ch>
Date:   Sat Sep 22 19:52:11 2012 +0200

    console: implement lockdep support for console_lock

On the patch itself:
- Switch CONFIG_FRAMEBUFFER_CONSOLE to be a boolean, using the overall
  CONFIG_FB tristate to decided whether it should be a module or
  built-in.

- At first I thought I could force the build depency with just a dummy
  symbol that fbcon.ko exports and fb.ko uses. But that leads to a
  module depency cycle (it works fine when built-in).

  Since this tight binding is the entire goal the simplest solution is
  to move all the fbcon modules (and there's a bunch of optinal
  source-files which are each modules of their own, for no good
  reason) into the overall fb.ko core module. That's a bit more than
  what I would have liked to do in this patch, but oh well.

Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Reviewed-by: Sean Paul <seanpaul@chromium.org>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
2017-08-01 17:32:07 +02:00
Ezequiel Garcia
5ec9653806 fbdev: Make fb-notify a no-op if CONFIG_FB=n
There's no point in having support for framebuffer notifications
is CONFIG_FB is disabled. This commit adds the necessary stubs
for code to link properly when CONFIG_FB=n and moves fb-notify.o
to be built only when CONFIG_FB=y.

Signed-off-by: Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
2015-12-15 15:41:24 +02:00
Harald Geyer
a7c42990f1 framebuffer: don't link fb_devio into kernel image unconditionally
CONFIG_FB_DEFERRED_IO is defined as bool while CONFIG_FB is defined as
tristate. Currently fb_defio.o is linked into the kernel image even if
CONFIG_FB=m.

I fix this by updating the Makefile to link fb_defio.o into fb.o and thus
go into one place with the other core framebuffer code.

Signed-off-by: Harald Geyer <harald@ccbib.org>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
2015-05-07 13:59:45 +03:00
Daniel Vetter
ea6763c104 video/fbdev: Always built-in video= cmdline parsing
In drm/i915 we want to get at the video= cmdline modes even when we
don't have fbdev support enabled, so that users can always override
the kernel's initial mode selection.

But that gives us a direct depency upon the parsing code in the fbdev
subsystem. Since it's so little code just extract these 2 functions
and always build them in.

Whiel at it fix the checkpatch fail in this code.

v2: Also move fb_mode_option. Spotted by the kbuild.

v3: Review from Geert:
- Keep the old copyright notice from fb_mem.c, although I have no
idea what exactly applies.
- Only compile this when needed.

Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Plagniol-Villard <plagnioj@jcrosoft.com>
Cc: Tomi Valkeinen <tomi.valkeinen@ti.com>
Cc: linux-fbdev@vger.kernel.org
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

--

I prefer if we can merge this through drm-next since we'll use it
there in follow-up patches.
-Daniel
2014-08-06 14:50:02 +02:00
Tomi Valkeinen
19757fc843 fbdev: move fbdev core files to separate directory
Instead of having fbdev framework core files at the root fbdev
directory, mixed with random fbdev device drivers, move the fbdev core
files to a separate core directory. This makes it much clearer which of
the files are actually part of the fbdev framework, and which are part
of device drivers.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Rob Clark <robdclark@gmail.com>
Acked-by: Jingoo Han <jg1.han@samsung.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
2014-04-17 08:10:19 +03:00