From 849369d6c66d3054688672f97d31fceb8e8230fb Mon Sep 17 00:00:00 2001 From: root Date: Fri, 25 Dec 2015 04:40:36 +0000 Subject: initial_commit --- Documentation/usb/ohci.txt | 32 ++++++++++++++++++++++++++++++++ 1 file changed, 32 insertions(+) create mode 100644 Documentation/usb/ohci.txt (limited to 'Documentation/usb/ohci.txt') diff --git a/Documentation/usb/ohci.txt b/Documentation/usb/ohci.txt new file mode 100644 index 00000000..99320d9f --- /dev/null +++ b/Documentation/usb/ohci.txt @@ -0,0 +1,32 @@ +23-Aug-2002 + +The "ohci-hcd" driver is a USB Host Controller Driver (HCD) that is derived +from the "usb-ohci" driver from the 2.4 kernel series. The "usb-ohci" code +was written primarily by Roman Weissgaerber but with +contributions from many others (read its copyright/licencing header). + +It supports the "Open Host Controller Interface" (OHCI), which standardizes +hardware register protocols used to talk to USB 1.1 host controllers. As +compared to the earlier "Universal Host Controller Interface" (UHCI) from +Intel, it pushes more intelligence into the hardware. USB 1.1 controllers +from vendors other than Intel and VIA generally use OHCI. + +Changes since the 2.4 kernel include + + - improved robustness; bugfixes; and less overhead + - supports the updated and simplified usbcore APIs + - interrupt transfers can be larger, and can be queued + - less code, by using the upper level "hcd" framework + - supports some non-PCI implementations of OHCI + - ... more + +The "ohci-hcd" driver handles all USB 1.1 transfer types. Transfers of all +types can be queued. That was also true in "usb-ohci", except for interrupt +transfers. Previously, using periods of one frame would risk data loss due +to overhead in IRQ processing. When interrupt transfers are queued, those +risks can be minimized by making sure the hardware always has transfers to +work on while the OS is getting around to the relevant IRQ processing. + +- David Brownell + + -- cgit v1.2.3