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[PATCH] VT binding: Update documentation

Browse source 
Update Documentation/fb/fbcon.txt and Documentatin/console/console.txt to
reflect the following changes:

1. sysfs attributes are relocated to /sys/class/vtconsole

2. feature is selectable in Kconfig

3. add sample scripts to fbcon.txt

Signed-off-by: Antonino Daplas <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Antonino A. Daplas 2006-06-26 00:27:14 -07:00 • committed by Linus Torvalds
commit 6690075d0b
2 changed files with 101 additions and 35 deletions
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67
Documentation/console/console.txt
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@ -27,45 +27,62 @@ In newer kernels, the following are also available:
register_con_driver()
unregister_con_driver()
If sysfs is enabled, the contents of /sys/class/tty/console/backend can be
examined. This shows the console drivers currently registered by the system. On
an x86 system with the framebuffer console enabled, the contents of this
attribute may be like this:
If sysfs is enabled, the contents of /sys/class/vtconsole can be
examined. This shows the console backends currently registered by the
system which are named vtcon<n> where <n> is an integer fro 0 to 15. Thus:
cat /sys/class/tty/console/backend
0 S: VGA+
1 B: frame buffer device
ls /sys/class/vtconsole
. .. vtcon0 vtcon1
The first line shows the VGA console driver, while the second line shows
the framebuffer console driver.
Each directory in /sys/class/vtconsole has 3 files:
The leftmost numeric character is the driver ID. The middle character with
the colon describes the status of the driver.
ls /sys/class/vtconsole/vtcon0
. .. bind name uevent
S: - system driver (binding unspecified)
B: - bound modular driver
U: - unbound modular driver
What do these files signify?
The last column is the description of the driver.
1. bind - this is a read/write file. It shows the status of the driver if
read, or acts to bind or unbind the driver to the virtual consoles
when written to. The possible values are:
Under /sys/class/tty/console are two other attributes, 'bind' and
'unbind'. What does these 2 attributes do? As their name implies, echo'ing the
driver ID to 'bind' will bind an unbound modular driver, and to 'unbind' will
unbind a bound modular driver. Echo'ing the ID of a system driver to either
attribute will do nothing.
0 - means the driver is not bound and if echo'ed, commands the driver
to unbind
Thus:
1 - means the driver is bound and if echo'ed, commands the driver to
bind
echo 1 > /sys/class/tty/console/unbind
cat /sys/class/tty/console/backend
0 S: VGA+
1 U: frame buffer device
2. name - read-only file. Shows the name of the driver in this format:
cat /sys/class/vtconsole/vtcon0/name
(S) VGA+
'(S)' stands for a (S)ystem driver, ie, it cannot be directly
commanded to bind or unbind
'VGA+' is the name of the driver
cat /sys/class/vtconsole/vtcon1/name
(M) frame buffer device
In this case, '(M)' stands for a (M)odular driver, one that can be
directly commanded to bind or unbind.
3. uevent - ignore this file
When unbinding, the modular driver is detached first, and then the system
driver takes over the consoles vacated by the driver. Binding, on the other
hand, will bind the driver to the consoles that are currently occupied by a
system driver.
NOTE1: Binding and binding must be selected in Kconfig. It's under:
Device Drivers -> Character devices -> Support for binding and unbinding
console drivers
NOTE2: If any of the virtual consoles are in KD_GRAPHICS mode, then binding or
unbinding will not succeed. An example of an application that sets the console
to KD_GRAPHICS is X.
How useful is this feature? This is very useful for console driver
developers. By unbinding the driver from the console layer, one can unload the
driver, make changes, recompile, reload and rebind the driver without any need