/* * We cannot tell prior to getting IOC facts how big the IOC's request * area is. Because of this we cannot tell at compile time how many * simple SG elements we can fit within an IOC request prior to having * to put in a chain element. * * Experimentally we know that the Ultra4 parts have a 96 byte request * element size and the Fibre Channel units have a 144 byte request * element size. Therefore, if we have 512-32 (== 480) bytes of request * area to play with, we have room for between 3 and 5 request sized * regions- the first of which is the command plus a simple SG list, * the rest of which are chained continuation SG lists. Given that the * normal request we use is 48 bytes w/o the first SG element, we can * assume we have 480-48 == 432 bytes to have simple SG elements and/or * chain elements. If we assume 32 bit addressing, this works out to * 54 SG or chain elements. If we assume 5 chain elements, then we have * a maximum of 49 separate actual SG segments. */