Documentation/usb/ohci.rst

Source file repositories/reference/linux-study-clean/Documentation/usb/ohci.rst

File Facts

System: Linux kernel
Corpus path: Documentation/usb/ohci.rst
Extension: .rst
Size: 1501 bytes
Lines: 36
Domain: Support Tooling And Documentation
Bucket: Documentation
Inferred role: Support Tooling And Documentation: documentation
Status: atlas-only

Why This File Exists

Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.

Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.

Dependency Surface

No C-style include directives detected by the generator.

Detected Declarations

No top-level syscall, struct, function, initcall, or export declaration detected by the generator.

Annotated Snippet

====
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>

Annotation

Atlas domain: Support Tooling And Documentation / Documentation.
Implementation status: atlas-only.

Implementation Notes

This generated page is the file-by-file coverage layer; curated subsystem chapters should link here when they synthesize a multi-file control flow.
Core OS pages should be promoted from atlas-only to deep-reviewed when they explain data structures, invariants, locking, lifecycle, and C implementation snippets.
Driver-family pages are intentionally pattern-oriented unless they are part of the selected PCIe/NVMe representative device path.