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authorAntonino A. Daplas <adaplas@gmail.com>2006-06-26 03:27:07 -0400
committerLinus Torvalds <torvalds@g5.osdl.org>2006-06-26 12:58:33 -0400
commita4a73e1f0283850edc143d28502c1c517c6ab49c (patch)
treec3e767bf8a3a19d0823d770357c472f70dde324a /Documentation/fb/fbcon.txt
parent5428b04405af1bb441aa8aabd314e48b870bc58e (diff)
[PATCH] Detaching fbcon: update documentation
Update Documentation/fb/fbcon.txt on the following: 1. sysfs attributes are now located in class/graphics/fbcon 2. instructions on how to attach, detach and/or unload fbcon Signed-off-by: Antonino Daplas <adaplas@pol.net> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'Documentation/fb/fbcon.txt')
-rw-r--r--Documentation/fb/fbcon.txt104
1 files changed, 100 insertions, 4 deletions
diff --git a/Documentation/fb/fbcon.txt b/Documentation/fb/fbcon.txt
index 08dce0f631bf..f3a3be087707 100644
--- a/Documentation/fb/fbcon.txt
+++ b/Documentation/fb/fbcon.txt
@@ -135,10 +135,10 @@ C. Boot options
135 135
136 The angle can be changed anytime afterwards by 'echoing' the same 136 The angle can be changed anytime afterwards by 'echoing' the same
137 numbers to any one of the 2 attributes found in 137 numbers to any one of the 2 attributes found in
138 /sys/class/graphics/fb{x} 138 /sys/class/graphics/fbcon
139 139
140 con_rotate - rotate the display of the active console 140 rotate - rotate the display of the active console
141 con_rotate_all - rotate the display of all consoles 141 rotate_all - rotate the display of all consoles
142 142
143 Console rotation will only become available if Console Rotation 143 Console rotation will only become available if Console Rotation
144 Support is compiled in your kernel. 144 Support is compiled in your kernel.
@@ -148,5 +148,101 @@ C. Boot options
148 Actually, the underlying fb driver is totally ignorant of console 148 Actually, the underlying fb driver is totally ignorant of console
149 rotation. 149 rotation.
150 150
151--- 151C. Attaching, Detaching and Unloading
152
153It's possible to detach/attach the framebuffer console from the vt layer by
154echoing anything to the following sysfs attributes found
155/sys/class/graphics/fbcon.
156
157 attach - attach framebuffer console to vt layer
158 detach - detach framebuffer console to vt layer
159
160If fbcon is detached from the vt layer, your boot console driver (which is
161usually VGA text mode) will take over. A few drivers (rivafb and i810fb) will
162restore VGA text mode for you. With the rest, before detaching fbcon, you
163must take a few additional steps to make sure that your VGA text mode is
164restored properly. The following is one of the several methods that you can do:
165
1661. Download or install vbetool. This utility is included with most
167 distributions nowadays, and is usually part of the suspend/resume tool.
168
1692. In your kernel configuration, ensure that CONFIG_FRAMEBUFFER_CONSOLE is set
170 to 'y' or 'm'. Enable one or more of your favorite framebuffer drivers.
171
1723. Boot into text mode and as root run:
173
174 vbetool vbestate save > <vga state file>
175
176 The above command saves the register contents of your graphics
177 hardware to <vga state file>. You need to do this step only once as
178 the state file can be reused.
179
1804. If fbcon is compiled as a module, load fbcon by doing:
181
182 modprobe fbcon
183
1845. Now to detach fbcon:
185
186 vbetool vbestate restore < <vga state file> && \
187 echo 1 > /sys/class/graphics/fbcon/detach
188
1896. That's it, you're back to VGA mode. And if you compiled your drivers as
190 modules, you can unload them at will. So if you want to change your driver
191 from xxxfb to yyyfb, you can do this:
192
193 detach fbcon
194 rmmod xxxfb
195 modprobe yyyfb
196
197 Of course, con2fbmap can do the same thing but will not work if xxxfb
198 and yyyfb are not compatible (ie, cannot be loaded at the same time).
199
2007. To reattach fbcon:
201
202 echo 1 > /sys/class/graphics/fbcon/attach
203
2048. Once the framebuffer console is detached, and if it is compiled as a module,
205the module can be unloaded with 'rmmod fbcon'. This feature is great for
206developers.
207
208Notes for vesafb users:
209=======================
210
211Unfortunately, if your bootline includes a vga=xxx parameter that sets the
212hardware in graphics mode, such as when loading vesafb, vgacon will not load.
213Instead, vgacon will replace the default boot console with dummycon, and you
214won't get any display after detaching fbcon. Your machine is still alive, so
215you can reattach vesafb. However, to reattach vesafb, you need to do one of
216the following:
217
218Variation 1:
219
220 a. Before detaching fbcon, do
221
222 vbetool vbemode save > <vesa state file> # do once for each vesafb mode,
223 # the file can be reused
224
225 b. Detach fbcon as in step 5.
226
227 c. Attach fbcon
228
229 vbetool vbestate restore < <vesa state file> && \
230 echo 1 > /sys/class/graphics/fbcon/attach
231
232Variation 2:
233
234 a. Before detaching fbcon, do:
235
236 vbetool vbemode get
237
238 b. Take note of the mode number
239
240 b. Detach fbcon as in step 5.
241
242 c. Attach fbcon:
243
244 vbetool vbemode set <mode number> && \
245 echo 1 > /sys/class/graphics/fbcon/attach
246
247--
152Antonino Daplas <adaplas@pol.net> 248Antonino Daplas <adaplas@pol.net>