Adding upstream version 6.6.15.upstream/6.6.15

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 35 insertions, 0 deletions

diff --git a/Documentation/usb/ohci.rst b/Documentation/usb/ohci.rst
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+====
+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>