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35 lines
1.5 KiB
35 lines
1.5 KiB
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OHCI |
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23-Aug-2002 |
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The "ohci-hcd" driver is a USB Host Controller Driver (HCD) that is derived |
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from the "usb-ohci" driver from the 2.4 kernel series. The "usb-ohci" code |
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was written primarily by Roman Weissgaerber <[email protected]> but with |
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contributions from many others (read its copyright/licencing header). |
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It supports the "Open Host Controller Interface" (OHCI), which standardizes |
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hardware register protocols used to talk to USB 1.1 host controllers. As |
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compared to the earlier "Universal Host Controller Interface" (UHCI) from |
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Intel, it pushes more intelligence into the hardware. USB 1.1 controllers |
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from vendors other than Intel and VIA generally use OHCI. |
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Changes since the 2.4 kernel include |
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- improved robustness; bugfixes; and less overhead |
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- supports the updated and simplified usbcore APIs |
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- interrupt transfers can be larger, and can be queued |
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- less code, by using the upper level "hcd" framework |
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- supports some non-PCI implementations of OHCI |
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- ... more |
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The "ohci-hcd" driver handles all USB 1.1 transfer types. Transfers of all |
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types can be queued. That was also true in "usb-ohci", except for interrupt |
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transfers. Previously, using periods of one frame would risk data loss due |
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to overhead in IRQ processing. When interrupt transfers are queued, those |
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risks can be minimized by making sure the hardware always has transfers to |
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work on while the OS is getting around to the relevant IRQ processing. |
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- David Brownell |
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<[email protected]>
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