what time does host will re-used the prplist memory region.

[Matthew Wilcox]

On Tue, Aug 04, 2015 at 11:29:47AM +0800, HavenYang wrote:
> It says the SQhead indicate Submission Queue entries may be re-used, but it not say the PRPlist related to this command may be re-used or not, I confused.
> 
> my question is:
> 1. from host side, what is the condition can host re-used the prplist memory region for a host command, SQHead or command complete?

The host can only reuse the PRP list memory when the command has been
completed.  The device is entitled to use the PRP list throughout
execution of the command.

> 2. from device side, what is the condition to update SQHead, fetched command head(simple) or fetched all prp from prplist(complex)?

The first; the host only takes this as an indication that it can reuse
the SQ entry.