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nvme: Export constants for min and max queue sizes
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Authored by jhb on Mar 20 2024, 11:23 PM.
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Summary

These are useful for NVMe over Fabrics.

Sponsored by: Chelsio Communications

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rG FreeBSD src repository
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sys/dev/nvme/nvme.h
71

Where does this number come from?

sys/dev/nvme/nvme.h
71

See 4.1.3 in the base NVMe spec 1.4b.

4.1.3 Queue Size

The Queue Size is indicated in a 16-bit 0’s based field that indicates the number of slots in the queue. The minimum size for a queue is two slots. The maximum size for either an I/O Submission Queue or an I/O Completion Queue is defined as 64 Ki slots, limited by the maximum queue size supported by the controller that is reported in the CAP.MQES field. The maximum size for the Admin Submission and Admin Completion Queue is defined as 4 Ki slots. One slot in each queue is not available for use due to Head and Tail entry pointer definition.

That is the source for all 4 of these numbers.

This revision was not accepted when it landed; it landed in state Needs Review.Mar 23 2024, 12:26 AM
This revision was automatically updated to reflect the committed changes.