The framebuffer console is now able to dynamically bind and unbind from the VT
console layer. Due to the way the VT console layer works, the drivers
themselves decide when to bind or unbind. However, it was decided that
binding must be controlled, not by the drivers themselves, but by the VT
console layer. With this, dynamic binding is possible for all VT console
drivers, not just fbcon.
Thus, the VT console layer will impose the following to all VT console
drivers:
- all registered VT console drivers will be entered in a private list
- drivers can register themselves to the VT console layer, but they cannot
decide when to bind or unbind. (Exception: To maintain backwards
compatibility, take_over_console() will automatically bind the driver after
registration.)
- drivers can remove themselves from the list by unregistering from the VT
console layer. A prerequisite for unregistration is that the driver must not
be bound.
The following functions are new in the vt.c:
register_con_driver() - public function, this function adds the VT console
driver to an internal list maintained by the VT console
bind_con_driver() - private function, it binds the driver to the console
take_over_console() is changed to call register_con_driver() followed by a
bind_con_driver(). This is the only time drivers can decide when to bind to
the VT layer. This is to maintain backwards compatibility.
unbind_con_driver() - private function, it unbinds the driver from its
console. The vacated consoles will be taken over by the default boot console
driver.
unregister_con_driver() - public function, removes the driver from the
internal list maintained by the VT console. It will only succeed if the
driver is currently unbound.
con_is_bound() checks if the driver is currently bound or not
give_up_console() is just a wrapper to unregister_con_driver().
There are also 3 additional functions meant to be called only by the tty layer
for sysfs control:
vt_bind() - calls bind_con_driver()
vt_unbind() - calls unbind_con_driver()
vt_show_drivers() - shows the list of registered drivers
Most VT console drivers will continue to work as is, but might have problems
when unbinding or binding which should be fixable with minimal changes.
Signed-off-by: Antonino Daplas <adaplas@pol.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Currently printk is no use for early debugging because it refuses to
actually print anything to the console unless
cpu_online(smp_processor_id()) is true.
The stated explanation is that console drivers may require per-cpu
resources, or otherwise barf, because the system is not yet setup
correctly. Fair enough.
However some console drivers might be quite happy running early during
boot, in fact we have one, and so it'd be nice if printk understood that.
So I added a flag (which I would have called CON_BOOT, but that's taken)
called CON_ANYTIME, which indicates that a console is happy to be called
anytime, even if the cpu is not yet online.
Tested on a Power 5 machine, with both a CON_ANYTIME driver and a bogus
console driver that BUG()s if called while offline. No problems AFAICT.
Built for i386 UP & SMP.
Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Trying to suspend/resume with console messages flying all around is
doomed to failure, when the devices that the messages are trying to
go to are being shut down.
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
Antonino A. Daplas