mirror of
https://github.com/team-infusion-developers/android_kernel_samsung_msm8976.git
synced 2024-11-01 10:33:27 +00:00
33 lines
1.5 KiB
Text
33 lines
1.5 KiB
Text
|
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 <weissg@vienna.at> 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
|
||
|
|
<dbrownell@users.sourceforge.net>
|
||
|
|
|