ecefae6db0
While there are a mix of things here, most of the stuff were written from Kernel developer's PoV. So, add them to the driver-api book. A follow up for this patch would be to move documents from there that are specific to sysadmins, adding them to the admin-guide. Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org> Acked-by: Johan Hovold <johan@kernel.org> Acked-by: Felipe Balbi <felipe.balbi@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
36 lines
1.5 KiB
ReStructuredText
36 lines
1.5 KiB
ReStructuredText
====
|
|
OHCI
|
|
====
|
|
|
|
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>
|