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-rw-r--r--Documentation/fb/viafb.txt48
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diff --git a/Documentation/fb/viafb.txt b/Documentation/fb/viafb.txt
index f3e046a6a98..1a2e8aa3fbb 100644
--- a/Documentation/fb/viafb.txt
+++ b/Documentation/fb/viafb.txt
@@ -197,6 +197,54 @@ Notes:
example,
# fbset -depth 16
+
+[Configure viafb via /proc]
+---------------------------
+ The following files exist in /proc/viafb
+
+ supported_output_devices
+
+ This read-only file contains a full ',' seperated list containing all
+ output devices that could be available on your platform. It is likely
+ that not all of those have a connector on your hardware but it should
+ provide a good starting point to figure out which of those names match
+ a real connector.
+ Example:
+ # cat /proc/viafb/supported_output_devices
+
+ iga1/output_devices
+ iga2/output_devices
+
+ These two files are readable and writable. iga1 and iga2 are the two
+ independent units that produce the screen image. Those images can be
+ forwarded to one or more output devices. Reading those files is a way
+ to query which output devices are currently used by an iga.
+ Example:
+ # cat /proc/viafb/iga1/output_devices
+ If there are no output devices printed the output of this iga is lost.
+ This can happen for example if only one (the other) iga is used.
+ Writing to these files allows adjusting the output devices during
+ runtime. One can add new devices, remove existing ones or switch
+ between igas. Essentially you can write a ',' seperated list of device
+ names (or a single one) in the same format as the output to those
+ files. You can add a '+' or '-' as a prefix allowing simple addition
+ and removal of devices. So a prefix '+' adds the devices from your list
+ to the already existing ones, '-' removes the listed devices from the
+ existing ones and if no prefix is given it replaces all existing ones
+ with the listed ones. If you remove devices they are expected to turn
+ off. If you add devices that are already part of the other iga they are
+ removed there and added to the new one.
+ Examples:
+ Add CRT as output device to iga1
+ # echo +CRT > /proc/viafb/iga1/output_devices
+
+ Remove (turn off) DVP1 and LVDS1 as output devices of iga2
+ # echo -DVP1,LVDS1 > /proc/viafb/iga2/output_devices
+
+ Replace all iga1 output devices by CRT
+ # echo CRT > /proc/viafb/iga1/output_devices
+
+
[Bootup with viafb]:
--------------------
Add the following line to your grub.conf: