[PATCH v2] dmadev: clarify last_idx documentation for completion APIs

[Bruce Richardson]

On Wed, Jul 15, 2026 at 11:36:30AM +0530, Raghavendra Ningoji wrote:
> The last_idx output parameter was documented identically for
> rte_dma_completed() and rte_dma_completed_status(), even though the two
> APIs have different semantics:
> 
> - rte_dma_completed() only reports operations that completed
>   successfully and stops at the first error, so its last_idx is the
>   ring_idx of the last successfully completed operation.
> - rte_dma_completed_status() reports all completed operations regardless
>   of status, so its last_idx is the last completed operation's ring_idx
>   irrespective of success or failure.
> 
> In both cases only up to nb_cpls operations are reported per call, so
> last_idx is the ring_idx of the last reported operation, which may not
> be the last operation the device has actually completed.
> 
> Clarify both descriptions to remove the ambiguity.
> 
> Fixes: 91e581e5c924 ("dmadev: add data plane API")
> 
> Signed-off-by: Raghavendra Ningoji <raghavendra.ningoji at amd.com>
> ---
> v2:
>  - Clarify (per Bruce Richardson) that last_idx is the ring_idx of the
>    last operation reported by the call, bounded by nb_cpls, which may not
>    be the last operation the device has actually completed.
> 
Acked-by: Bruce Richardson <bruce.richardson at intel.com>