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How to increase BUlk MaxTransferSize for a virtual usb HCD?

DD-3DD-3 Member Posts: 17
I have a virtual usb HCD driver(something like usb over IP). I am receiving max. 256KB transfer size(TransferBufferLengthon) on Bulk OUT endpoints from usb client drivers in Windows 7. Is there any way to increase the transfer size?

Comments

  • Tim_RobertsTim_Roberts Member - All Emails Posts: 13,403
    [email protected] wrote:
    > I have a virtual usb HCD driver(something like usb over IP). I am receiving max. 256KB transfer size(TransferBufferLengthon) on Bulk OUT endpoints from usb client drivers in Windows 7. Is there any way to increase the transfer size?

    What kind of HCD do you emulate?

    This is up to the individual client drivers. EHCI and UHCI HCDs allow
    up to 4MB, but OHCI HCDs running at full speed are limited to 256kB, and
    as a result some clients adopted that limit. The USB storage driver
    gets its max transfer size from a registry entry; there are web hits
    showing how to hack that value.

    However, I'm wondering why you would care. In order to support audio
    and video devices, you have to emulate the packet timing of a real HCD
    pretty closely. It's not clear to me what you would gain through larger
    transfer sizes.

    --
    Tim Roberts, [email protected]
    Providenza & Boekelheide, Inc.

    Tim Roberts, [email protected]
    Providenza & Boekelheide, Inc.

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