a20: issue a null command after toggling the KBC
authorH. Peter Anvin <hpa@zytor.com>
Fri, 27 Jun 2008 20:09:13 +0000 (13:09 -0700)
committerH. Peter Anvin <hpa@zytor.com>
Fri, 27 Jun 2008 20:09:13 +0000 (13:09 -0700)
commitdb2a9ea510c3561a937574338740edffc118bc0d
tree09345ff9fab46e7a6c6c5d8bc18972ef525fcc0c
parent864690516dfbdeabb725a054edbe37b5541679c5
a20: issue a null command after toggling the KBC

Issue a null command after toggling the KBC, to avoid confusing UHCI
USB controllers.  Apparently DOS did this, probably for
synchronization reasons, and the UHCI specification took it as the end
of the A20 toggle sequence.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
reloc/a20.S