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Add a small README with information on the generic ohci driver.
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doc/README.generic_usb_ohci
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doc/README.generic_usb_ohci
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Notes on the the generic USB-OHCI driver
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========================================
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This driver (drivers/usb_ohci.[ch]) is the result of the merge of
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various existing OHCI drivers that were basically identical beside
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cpu/board dependant initalization. This initalization has been moved
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into cpu/board directories and are called via the hooks below.
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Configuration options
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----------------------
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CONFIG_USB_OHCI_NEW: enable the new OHCI driver
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CFG_USB_OHCI_BOARD_INIT: call the board dependant hooks:
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- extern int usb_board_init(void);
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- extern int usb_board_stop(void);
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- extern int usb_cpu_init_fail(void);
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CFG_USB_OHCI_CPU_INIT: call the cpu dependant hooks:
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- extern int usb_cpu_init(void);
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- extern int usb_cpu_stop(void);
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- extern int usb_cpu_init_fail(void);
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CFG_USB_OHCI_REGS_BASE: defines the base address of the OHCI registers
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CFG_USB_OHCI_SLOT_NAME: slot name
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CFG_USB_OHCI_MAX_ROOT_PORTS: maximal number of ports of the root hub.
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Endianness issues
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------------------
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The LITTLEENDIAN #define determines if the 'swap_16' and 'swap_32'
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macros do byte swapping or not. But some cpus OHCI-controllers such as
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ppc4xx and mpc5xxx operate in little endian mode, so some extra ifdefs
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were necessary to make this work.
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