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[PATCH] VT binding: Update documentation
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 <adaplas@pol.net> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Antonino A. Daplas
Linus Torvalds
parent
5bd42536b3
commit
6690075d0b
2 changed files with 101 additions and 35 deletions
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@ -27,45 +27,62 @@ In newer kernels, the following are also available:
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register_con_driver()
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unregister_con_driver()
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If sysfs is enabled, the contents of /sys/class/tty/console/backend can be
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examined. This shows the console drivers currently registered by the system. On
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an x86 system with the framebuffer console enabled, the contents of this
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attribute may be like this:
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If sysfs is enabled, the contents of /sys/class/vtconsole can be
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examined. This shows the console backends currently registered by the
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system which are named vtcon<n> where <n> is an integer fro 0 to 15. Thus:
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cat /sys/class/tty/console/backend
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0 S: VGA+
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1 B: frame buffer device
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ls /sys/class/vtconsole
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. .. vtcon0 vtcon1
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The first line shows the VGA console driver, while the second line shows
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the framebuffer console driver.
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Each directory in /sys/class/vtconsole has 3 files:
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The leftmost numeric character is the driver ID. The middle character with
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the colon describes the status of the driver.
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ls /sys/class/vtconsole/vtcon0
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. .. bind name uevent
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S: - system driver (binding unspecified)
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B: - bound modular driver
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U: - unbound modular driver
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What do these files signify?
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The last column is the description of the driver.
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1. bind - this is a read/write file. It shows the status of the driver if
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read, or acts to bind or unbind the driver to the virtual consoles
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when written to. The possible values are:
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Under /sys/class/tty/console are two other attributes, 'bind' and
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'unbind'. What does these 2 attributes do? As their name implies, echo'ing the
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driver ID to 'bind' will bind an unbound modular driver, and to 'unbind' will
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unbind a bound modular driver. Echo'ing the ID of a system driver to either
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attribute will do nothing.
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0 - means the driver is not bound and if echo'ed, commands the driver
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to unbind
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Thus:
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1 - means the driver is bound and if echo'ed, commands the driver to
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bind
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echo 1 > /sys/class/tty/console/unbind
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cat /sys/class/tty/console/backend
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0 S: VGA+
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1 U: frame buffer device
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2. name - read-only file. Shows the name of the driver in this format:
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cat /sys/class/vtconsole/vtcon0/name
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(S) VGA+
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'(S)' stands for a (S)ystem driver, ie, it cannot be directly
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commanded to bind or unbind
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'VGA+' is the name of the driver
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cat /sys/class/vtconsole/vtcon1/name
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(M) frame buffer device
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In this case, '(M)' stands for a (M)odular driver, one that can be
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directly commanded to bind or unbind.
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3. uevent - ignore this file
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When unbinding, the modular driver is detached first, and then the system
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driver takes over the consoles vacated by the driver. Binding, on the other
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hand, will bind the driver to the consoles that are currently occupied by a
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system driver.
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NOTE1: Binding and binding must be selected in Kconfig. It's under:
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Device Drivers -> Character devices -> Support for binding and unbinding
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console drivers
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NOTE2: If any of the virtual consoles are in KD_GRAPHICS mode, then binding or
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unbinding will not succeed. An example of an application that sets the console
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to KD_GRAPHICS is X.
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How useful is this feature? This is very useful for console driver
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developers. By unbinding the driver from the console layer, one can unload the
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driver, make changes, recompile, reload and rebind the driver without any need
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@ -180,10 +180,13 @@ fbcon.
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So, how do we unbind fbcon from the console? Part of the answer is in
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Documentation/console/console.txt. To summarize:
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Echo the ID number of the 'frame buffer driver' to:
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Echo a value to the bind file that represents the framebuffer console
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driver. So assuming vtcon1 represents fbcon, then:
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sys/class/tty/console/bind - attach framebuffer console to console layer
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sys/class/tty/console/unbind - detach framebuffer console from console layer
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echo 1 > sys/class/vtconsole/vtcon1/bind - attach framebuffer console to
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console layer
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echo 0 > sys/class/vtconsole/vtcon1/bind - detach framebuffer console from
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console layer
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If fbcon is detached from the console layer, your boot console driver (which is
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usually VGA text mode) will take over. A few drivers (rivafb and i810fb) will
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@ -211,19 +214,15 @@ restored properly. The following is one of the several methods that you can do:
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5. Now to detach fbcon:
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'cat /sys/class/tty/console/backend' and take note of the ID
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The above is probably needed only once. Then:
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vbetool vbestate restore < <vga state file> && \
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echo <ID> > /sys/class/tty/console/unbind
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echo 0 > /sys/class/vtconsole/vtcon1/bind
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6. That's it, you're back to VGA mode. And if you compiled fbcon as a module,
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you can unload it by 'rmmod fbcon'
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7. To reattach fbcon:
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echo <ID> > /sys/class/tty/console/bind
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echo 1 > /sys/class/vtconsole/vtcon1/bind
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8. Once fbcon is unbound, all drivers registered to the system will also
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become unbound. This means that fbcon and individual framebuffer drivers
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@ -254,6 +253,8 @@ Variation 1:
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c. Attach fbcon
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vbetool vbestate restore < <vesa state file> && \
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echo 1 > /sys/class/vtconsole/vtcon1/bind
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Variation 2:
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a. Before detaching fbcon, do:
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@ -269,7 +270,55 @@ Variation 2:
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c. Attach fbcon:
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vbetool vbemode set <mode number> && \
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echo <ID> > /sys/class/tty/console/bind
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echo 1 > /sys/class/vtconsole/vtcon1/bind
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Samples:
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========
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Here are 2 sample bash scripts that you can use to bind or unbind the
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framebuffer console driver if you are in an X86 box:
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---------------------------------------------------------------------------
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#!/bin/bash
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# Unbind fbcon
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# Change this to where your actual vgastate file is located
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# Or Use VGASTATE=$1 to indicate the state file at runtime
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VGASTATE=/tmp/vgastate
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# path to vbetool
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VBETOOL=/usr/local/bin
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for (( i = 0; i < 16; i++))
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do
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if test -x /sys/class/vtconsole/vtcon$i; then
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if [ `cat /sys/class/vtconsole/vtcon$i/name | grep -c "frame buffer"` \
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= 1 ]; then
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if test -x $VBETOOL/vbetool; then
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echo Unbinding vtcon$i
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$VBETOOL/vbetool vbestate restore < $VGASTATE
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echo 0 > /sys/class/vtconsole/vtcon$i/bind
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fi
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fi
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fi
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done
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---------------------------------------------------------------------------
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#!/bin/bash
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# Bind fbcon
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for (( i = 0; i < 16; i++))
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do
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if test -x /sys/class/vtconsole/vtcon$i; then
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if [ `cat /sys/class/vtconsole/vtcon$i/name | grep -c "frame buffer"` \
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= 1 ]; then
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echo Unbinding vtcon$i
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echo 1 > /sys/class/vtconsole/vtcon$i/bind
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fi
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fi
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done
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---------------------------------------------------------------------------
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--
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Antonino Daplas <adaplas@pol.net>
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