1*4882a593Smuzhiyun==== 2*4882a593SmuzhiyunOHCI 3*4882a593Smuzhiyun==== 4*4882a593Smuzhiyun 5*4882a593Smuzhiyun23-Aug-2002 6*4882a593Smuzhiyun 7*4882a593SmuzhiyunThe "ohci-hcd" driver is a USB Host Controller Driver (HCD) that is derived 8*4882a593Smuzhiyunfrom the "usb-ohci" driver from the 2.4 kernel series. The "usb-ohci" code 9*4882a593Smuzhiyunwas written primarily by Roman Weissgaerber <weissg@vienna.at> but with 10*4882a593Smuzhiyuncontributions from many others (read its copyright/licencing header). 11*4882a593Smuzhiyun 12*4882a593SmuzhiyunIt supports the "Open Host Controller Interface" (OHCI), which standardizes 13*4882a593Smuzhiyunhardware register protocols used to talk to USB 1.1 host controllers. As 14*4882a593Smuzhiyuncompared to the earlier "Universal Host Controller Interface" (UHCI) from 15*4882a593SmuzhiyunIntel, it pushes more intelligence into the hardware. USB 1.1 controllers 16*4882a593Smuzhiyunfrom vendors other than Intel and VIA generally use OHCI. 17*4882a593Smuzhiyun 18*4882a593SmuzhiyunChanges since the 2.4 kernel include 19*4882a593Smuzhiyun 20*4882a593Smuzhiyun - improved robustness; bugfixes; and less overhead 21*4882a593Smuzhiyun - supports the updated and simplified usbcore APIs 22*4882a593Smuzhiyun - interrupt transfers can be larger, and can be queued 23*4882a593Smuzhiyun - less code, by using the upper level "hcd" framework 24*4882a593Smuzhiyun - supports some non-PCI implementations of OHCI 25*4882a593Smuzhiyun - ... more 26*4882a593Smuzhiyun 27*4882a593SmuzhiyunThe "ohci-hcd" driver handles all USB 1.1 transfer types. Transfers of all 28*4882a593Smuzhiyuntypes can be queued. That was also true in "usb-ohci", except for interrupt 29*4882a593Smuzhiyuntransfers. Previously, using periods of one frame would risk data loss due 30*4882a593Smuzhiyunto overhead in IRQ processing. When interrupt transfers are queued, those 31*4882a593Smuzhiyunrisks can be minimized by making sure the hardware always has transfers to 32*4882a593Smuzhiyunwork on while the OS is getting around to the relevant IRQ processing. 33*4882a593Smuzhiyun 34*4882a593Smuzhiyun- David Brownell 35*4882a593Smuzhiyun <dbrownell@users.sourceforge.net> 36