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author | Linus Torvalds <torvalds@ppc970.osdl.org> | 2005-04-16 15:20:36 -0700 |
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committer | Linus Torvalds <torvalds@ppc970.osdl.org> | 2005-04-16 15:20:36 -0700 |
commit | 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch) | |
tree | 0bba044c4ce775e45a88a51686b5d9f90697ea9d /Documentation/i386/usb-legacy-support.txt | |
download | linux-1da177e4c3f41524e886b7f1b8a0c1fc7321cac2.tar.bz2 |
Linux-2.6.12-rc2v2.6.12-rc2
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
Diffstat (limited to 'Documentation/i386/usb-legacy-support.txt')
-rw-r--r-- | Documentation/i386/usb-legacy-support.txt | 44 |
1 files changed, 44 insertions, 0 deletions
diff --git a/Documentation/i386/usb-legacy-support.txt b/Documentation/i386/usb-legacy-support.txt new file mode 100644 index 000000000000..1894cdfc69d9 --- /dev/null +++ b/Documentation/i386/usb-legacy-support.txt @@ -0,0 +1,44 @@ +USB Legacy support +~~~~~~~~~~~~~~~~~~ + +Vojtech Pavlik <vojtech@suse.cz>, January 2004 + + +Also known as "USB Keyboard" or "USB Mouse support" in the BIOS Setup is a +feature that allows one to use the USB mouse and keyboard as if they were +their classic PS/2 counterparts. This means one can use an USB keyboard to +type in LILO for example. + +It has several drawbacks, though: + +1) On some machines, the emulated PS/2 mouse takes over even when no USB + mouse is present and a real PS/2 mouse is present. In that case the extra + features (wheel, extra buttons, touchpad mode) of the real PS/2 mouse may + not be available. + +2) If CONFIG_HIGHMEM64G is enabled, the PS/2 mouse emulation can cause + system crashes, because the SMM BIOS is not expecting to be in PAE mode. + The Intel E7505 is a typical machine where this happens. + +3) If AMD64 64-bit mode is enabled, again system crashes often happen, + because the SMM BIOS isn't expecting the CPU to be in 64-bit mode. The + BIOS manufacturers only test with Windows, and Windows doesn't do 64-bit + yet. + +Solutions: + +Problem 1) can be solved by loading the USB drivers prior to loading the +PS/2 mouse driver. Since the PS/2 mouse driver is in 2.6 compiled into +the kernel unconditionally, this means the USB drivers need to be +compiled-in, too. + +Problem 2) can currently only be solved by either disabling HIGHMEM64G +in the kernel config or USB Legacy support in the BIOS. A BIOS update +could help, but so far no such update exists. + +Problem 3) is usually fixed by a BIOS update. Check the board +manufacturers web site. If an update is not available, disable USB +Legacy support in the BIOS. If this alone doesn't help, try also adding +idle=poll on the kernel command line. The BIOS may be entering the SMM +on the HLT instruction as well. + |