[nvmewin] updated SGL conversion routine

[Luse, Paul E]

OK, the else has now been updated (thanks Jim, needed some tweaks though but I saw what you were going for of course).  There's so many way to handle this problem, I'm sure we can find something more efficient than this but its pretty good I think and easy to follow.

Please review, I have this under test now and am heading out....

Thx
Paul


        physicalAddress.QuadPart = pSgl->List[index].PhysicalAddress.QuadPart;

        if (sgElementSize <= PAGE_SIZE) {
            ULONG nextPage = 0;

            /* Must transfer at least one full page */
            numImplicitEntries = 1;
            /*
             * since we may be offset into the page, look to determine
             * address to determine if a 2nd PRP entry is needed
             */
            nextPage = physicalAddress.LowPart + PAGE_SIZE;
            nextPage = nextPage & ~PAGE_MASK;
            numImplicitEntries +=
                ((physicalAddress.LowPart + sgElementSize) > nextPage) ? 1 : 0;
        } else {
            PHYSICAL_ADDRESS startAddr, endAddr;

            startAddr.QuadPart = physicalAddress.QuadPart;
            endAddr.QuadPart = startAddr.QuadPart + sgElementSize;
            numImplicitEntries = 0;

            /* account for an entry becaue of an offset start */
            if (startAddr.QuadPart % PAGE_SIZE) {
                numImplicitEntries += 1;
                /* bump the start address to the next page boundary */
                startAddr.QuadPart += PAGE_SIZE;
                startAddr.QuadPart &= ~PAGE_MASK;
            }

            /* account for an entry becaue of tail */
            if (endAddr.QuadPart % PAGE_SIZE) {
                numImplicitEntries += 1;
                /* lop off the tail */
                endAddr.QuadPart &= ~PAGE_MASK;
            }
            /* now account for the whole pages if any */
            numImplicitEntries += (ULONG)((endAddr.QuadPart - startAddr.QuadPart) / PAGE_SIZE);
        }

____________________________________
Paul Luse
Sr. Staff Engineer
PCG Server Software Engineering
Desk: 480.554.3688, Mobile: 480.334.4630

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