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kIOUSBTooManyPipesErr
A host-side interface limit was exceeded
kIOUSBTooManyPipesErr means that the requested operation would use more pipes than the interface allows. A pipe is associated with an endpoint in the currently selected configuration and interface setting, so the limit must be evaluated in that scope. It is not a general statement that the device has too many physical connectors or that all USB bandwidth is exhausted.
Repeated open or setup operations after reconnect, recovery, or alternate-setting changes can create this condition if the application fails to release its old interface state. The diagnostic should identify the sequence of pipe creation and destruction, not only the endpoint that triggered the final error.
Find the excess allocation
- Track every pipe by configuration, interface, alternate setting, endpoint address, direction, and owner.
- Verify that cleanup after timeout, disconnect, or reset is complete before reopening the same interface.
- Compare the requested pipe count with the endpoint descriptors for the active alternate setting.
- Do not fix the condition by opening a different endpoint arbitrarily; first establish the intended interface contract.
References
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