[PATCH] VT binding: Update documentation (6690075d) · Commits · 戴 / test

Documentation/console/console.txt

+42 −25

Original line number	Diff line number	Diff line
		@@ -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

Documentation/fb/fbcon.txt

+59 −10

Original line number	Diff line number	Diff line
		@@ -180,10 +180,13 @@ fbcon.
		So, how do we unbind fbcon from the console? Part of the answer is in
		Documentation/console/console.txt. To summarize:

		Echo the ID number of the 'frame buffer driver' to:
		Echo a value to the bind file that represents the framebuffer console
		driver. So assuming vtcon1 represents fbcon, then:

		sys/class/tty/console/bind - attach framebuffer console to console layer
		sys/class/tty/console/unbind - detach framebuffer console from console layer
		echo 1 > sys/class/vtconsole/vtcon1/bind - attach framebuffer console to
		console layer
		echo 0 > sys/class/vtconsole/vtcon1/bind - detach framebuffer console from
		console layer

		If fbcon is detached from the console layer, your boot console driver (which is
		usually VGA text mode) will take over. A few drivers (rivafb and i810fb) will
		@@ -211,19 +214,15 @@ restored properly. The following is one of the several methods that you can do:

		5. Now to detach fbcon:

		'cat /sys/class/tty/console/backend' and take note of the ID

		The above is probably needed only once. Then:

		vbetool vbestate restore < <vga state file> && \
		echo <ID> > /sys/class/tty/console/unbind
		echo 0 > /sys/class/vtconsole/vtcon1/bind

		6. That's it, you're back to VGA mode. And if you compiled fbcon as a module,
		you can unload it by 'rmmod fbcon'

		7. To reattach fbcon:

		echo <ID> > /sys/class/tty/console/bind
		echo 1 > /sys/class/vtconsole/vtcon1/bind

		8. Once fbcon is unbound, all drivers registered to the system will also
		become unbound. This means that fbcon and individual framebuffer drivers
		@@ -254,6 +253,8 @@ Variation 1:
		c. Attach fbcon

		vbetool vbestate restore < <vesa state file> && \
		echo 1 > /sys/class/vtconsole/vtcon1/bind

		Variation 2:

		a. Before detaching fbcon, do:
		@@ -269,7 +270,55 @@ Variation 2:
		c. Attach fbcon:

		vbetool vbemode set <mode number> && \
		echo <ID> > /sys/class/tty/console/bind
		echo 1 > /sys/class/vtconsole/vtcon1/bind

		Samples:
		========

		Here are 2 sample bash scripts that you can use to bind or unbind the
		framebuffer console driver if you are in an X86 box:

		---------------------------------------------------------------------------
		#!/bin/bash
		# Unbind fbcon

		# Change this to where your actual vgastate file is located
		# Or Use VGASTATE=$1 to indicate the state file at runtime
		VGASTATE=/tmp/vgastate

		# path to vbetool
		VBETOOL=/usr/local/bin


		for (( i = 0; i < 16; i++))
		do
		if test -x /sys/class/vtconsole/vtcon$i; then
		if [ `cat /sys/class/vtconsole/vtcon$i/name \| grep -c "frame buffer"` \
		= 1 ]; then
		if test -x $VBETOOL/vbetool; then
		echo Unbinding vtcon$i
		$VBETOOL/vbetool vbestate restore < $VGASTATE
		echo 0 > /sys/class/vtconsole/vtcon$i/bind
		fi
		fi
		fi
		done

		---------------------------------------------------------------------------
		#!/bin/bash
		# Bind fbcon

		for (( i = 0; i < 16; i++))
		do
		if test -x /sys/class/vtconsole/vtcon$i; then
		if [ `cat /sys/class/vtconsole/vtcon$i/name \| grep -c "frame buffer"` \
		= 1 ]; then
		echo Unbinding vtcon$i
		echo 1 > /sys/class/vtconsole/vtcon$i/bind
		fi
		fi
		done
		---------------------------------------------------------------------------

		--
		Antonino Daplas <adaplas@pol.net>

Admin message