ohci.rst (1501B)
1==== 2OHCI 3==== 4 523-Aug-2002 6 7The "ohci-hcd" driver is a USB Host Controller Driver (HCD) that is derived 8from the "usb-ohci" driver from the 2.4 kernel series. The "usb-ohci" code 9was written primarily by Roman Weissgaerber <weissg@vienna.at> but with 10contributions from many others (read its copyright/licencing header). 11 12It supports the "Open Host Controller Interface" (OHCI), which standardizes 13hardware register protocols used to talk to USB 1.1 host controllers. As 14compared to the earlier "Universal Host Controller Interface" (UHCI) from 15Intel, it pushes more intelligence into the hardware. USB 1.1 controllers 16from vendors other than Intel and VIA generally use OHCI. 17 18Changes since the 2.4 kernel include 19 20 - improved robustness; bugfixes; and less overhead 21 - supports the updated and simplified usbcore APIs 22 - interrupt transfers can be larger, and can be queued 23 - less code, by using the upper level "hcd" framework 24 - supports some non-PCI implementations of OHCI 25 - ... more 26 27The "ohci-hcd" driver handles all USB 1.1 transfer types. Transfers of all 28types can be queued. That was also true in "usb-ohci", except for interrupt 29transfers. Previously, using periods of one frame would risk data loss due 30to overhead in IRQ processing. When interrupt transfers are queued, those 31risks can be minimized by making sure the hardware always has transfers to 32work on while the OS is getting around to the relevant IRQ processing. 33 34- David Brownell 35 <dbrownell@users.sourceforge.net>