| 摘要 |
A method and apparatus of reporting the status of data transfer between software and hardware in a computer system is disclosed. Software provides empty descriptors to the hardware for posting completion updates of transfers. More particularly, the software provides the number of the last available descriptor to a first storage field in a storage location which is accessible to the hardware. The hardware accounts for the number of the descriptors it has used for reporting completion updates by posting the number of used descriptors to a second storage field in the storage location. To determine if more descriptors are available, the hardware compares the contents of the first storage field to that of the second storage field. If the contents of the first and second storage fields are equal, the hardware has reached the last descriptor in the completion ring. If the fields are not equal, one or more descriptors are available for the hardware to use.
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