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author | Jonathan Corbet <corbet@lwn.net> | 2023-03-15 02:06:44 +0300 |
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committer | Jonathan Corbet <corbet@lwn.net> | 2023-03-30 21:58:51 +0300 |
commit | ff61f0791ce969d2db6c9f3b71d74ceec0a2e958 (patch) | |
tree | fe32be44aaf65f9c436a8f37cd4a18f6ec47c3cb /Documentation/arch/x86/usb-legacy-support.rst | |
parent | f030c8fd64cea916d57d40bb7b59c1cff9ea3bc3 (diff) | |
download | linux-ff61f0791ce969d2db6c9f3b71d74ceec0a2e958.tar.xz |
docs: move x86 documentation into Documentation/arch/
Move the x86 documentation under Documentation/arch/ as a way of cleaning
up the top-level directory and making the structure of our docs more
closely match the structure of the source directories it describes.
All in-kernel references to the old paths have been updated.
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: linux-arch@vger.kernel.org
Cc: x86@kernel.org
Cc: Borislav Petkov <bp@alien8.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/lkml/20230315211523.108836-1-corbet@lwn.net/
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Diffstat (limited to 'Documentation/arch/x86/usb-legacy-support.rst')
-rw-r--r-- | Documentation/arch/x86/usb-legacy-support.rst | 50 |
1 files changed, 50 insertions, 0 deletions
diff --git a/Documentation/arch/x86/usb-legacy-support.rst b/Documentation/arch/x86/usb-legacy-support.rst new file mode 100644 index 000000000000..e01c08b7c981 --- /dev/null +++ b/Documentation/arch/x86/usb-legacy-support.rst @@ -0,0 +1,50 @@ + +.. SPDX-License-Identifier: GPL-2.0 + +================== +USB Legacy support +================== + +:Author: 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. |