# ConnectQueues Creates and configures the buffers that store the data moving to and from the device. ``` virtual kern_return_t ConnectQueues(IOBufferMemoryDescriptor **ifmd, IOMemoryDescriptor **rxqmd, IOMemoryDescriptor **txqmd, IOMemoryDescriptor *in_rxqmd, IOMemoryDescriptor *in_txqmd, uint32_t in_rxqoffset, uint32_t in_txqoffset, uint8_t in_rxqlogsz, uint8_t in_txqlogsz); ``` ## Parameters `ifmd` On return, a pointer to the memory buffer for storing interrupt-related data. `rxqmd` On return, a pointer to the memory buffer for storing data received from the device. `txqmd` On return, a pointer to the memory buffer for storing data ready to transmit to the device. `in_rxqmd` An existing memory buffer to configure and return in the `rxqmd` parameter. Specify `NULL` if you want this method to create the memory buffer for you. If you specify your own buffer object, this method retains it. `in_txqmd` An existing memory buffer to configure and return in the `txqmd` parameter. Specify `NULL` if you want this method to create the memory buffer for you. If you specify your own buffer object, this method retains it. `in_rxqoffset` The offset, in bytes, to the beginning of the `in_rxqmd` buffer. The offset represents the location at which the system starts accessing the buffer data. Specify `0` to indicate the beginning of the memory buffer. `in_txqoffset` The offset, in bytes, to the beginning of the `in_txqmd` buffer. The offset represents the location at which the system starts accessing the buffer data. Specify `0` to indicate the beginning of the memory buffer. `in_rxqlogsz` The base-2 logarithmic size of the buffer in the `in_rxqmd` parameter. For example, specify `14` for a buffer that is 16 kilobytes (2^14 bytes) in size. If `in_rxqmd` is `NULL`, this method creates a 16k buffer regardless of the value in this parameter. `in_txqlogsz` The base-2 logarithmic size of the buffer in the `in_txqmd` parameter. For example, specify `14` for a buffer that is 16 kilobytes (2^14 bytes) in size. If `in_txqmd` is `NULL`, this method creates a 16k buffer regardless of the value in this parameter. ## Return Value on success, or another value if an error occurs. See . ## Discussion When creating a custom serial driver, use this method to create or register the buffers that your driver uses to store data moving to and from the device. If you want to provide the memory buffers yourself, specify those values in the `in_rxqmd` and `in_txqmd` parameters. When creating custom buffers, always make the size of your buffers a power of 2. If you specify `NULL` for `in_rxqmd` and `in_txqmd`, this method creates new buffers for you. This method returns pointers to the buffers in the `rxqmd` and `txqmd` parameters. It also returns the system-created buffer for storing interrupt-related data in the `ifmd` parameter. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)