[IA64] Fix simscsi for new SCSI midlayer

The sd driver now uses scsi_execute_req() for almost everything.
scsi_execute_req() converts requests into scatterlists.

Fix the HP SCSI disk simulator to understand scatterlists for
more commands.

Without this patch the current kernel will not boot on the simulator
(the disks are always detected as having no sectors, and so cannot be
mounted).

Signed-off-by: Peter Chubb <peterc@gelato.unsw.edu.au>
Signed-off-by: Tony Luck <tony.luck@intel.com>

arch/ia64/hp/sim/simscsi.c

@@ -233,13 +233,31 @@ simscsi_readwrite10 (struct scsi_cmnd *sc, int mode)
 		simscsi_readwrite(sc, mode, offset, ((sc->cmnd[7] << 8) | sc->cmnd[8])*512);
 }
 
+static void simscsi_fillresult(struct scsi_cmnd *sc, char *buf, unsigned len)
+{
+
+	int scatterlen = sc->use_sg;
+	struct scatterlist *slp;
+
+	if (scatterlen == 0)
+		memcpy(sc->request_buffer, buf, len);
+	else for (slp = (struct scatterlist *)sc->buffer; scatterlen-- > 0 && len > 0; slp++) {
+		unsigned thislen = min(len, slp->length);
+
+		memcpy(page_address(slp->page) + slp->offset, buf, thislen);
+		slp++;
+		len -= thislen;
+	}
+}
+
 static int
 simscsi_queuecommand (struct scsi_cmnd *sc, void (*done)(struct scsi_cmnd *))
 {
 	unsigned int target_id = sc->device->id;
 	char fname[MAX_ROOT_LEN+16];
 	size_t disk_size;
 	char *buf;
+	char localbuf[36];
 #if DEBUG_SIMSCSI
 	register long sp asm ("sp");
 
@@ -263,7 +281,7 @@ simscsi_queuecommand (struct scsi_cmnd *sc, void (*done)(struct scsi_cmnd *))
 				/* disk doesn't exist... */
 				break;
 			}
-			buf = sc->request_buffer;
+			buf = localbuf;
 			buf[0] = 0;	/* magnetic disk */
 			buf[1] = 0;	/* not a removable medium */
 			buf[2] = 2;	/* SCSI-2 compliant device */
@@ -273,6 +291,7 @@ simscsi_queuecommand (struct scsi_cmnd *sc, void (*done)(struct scsi_cmnd *))
 			buf[6] = 0;	/* reserved */
 			buf[7] = 0;	/* various flags */
 			memcpy(buf + 8, "HP      SIMULATED DISK  0.00",  28);
+			simscsi_fillresult(sc, buf, 36);
 			sc->result = GOOD;
 			break;
 
@@ -304,16 +323,13 @@ simscsi_queuecommand (struct scsi_cmnd *sc, void (*done)(struct scsi_cmnd *))
 			simscsi_readwrite10(sc, SSC_WRITE);
 			break;
 
-
 		      case READ_CAPACITY:
 			if (desc[target_id] < 0 || sc->request_bufflen < 8) {
 				break;
 			}
-			buf = sc->request_buffer;
-
+			buf = localbuf;
 			disk_size = simscsi_get_disk_size(desc[target_id]);
 
-			/* pretend to be a 1GB disk (partition table contains real stuff): */
 			buf[0] = (disk_size >> 24) & 0xff;
 			buf[1] = (disk_size >> 16) & 0xff;
 			buf[2] = (disk_size >>  8) & 0xff;
@@ -323,13 +339,14 @@ simscsi_queuecommand (struct scsi_cmnd *sc, void (*done)(struct scsi_cmnd *))
 			buf[5] = 0;
 			buf[6] = 2;
 			buf[7] = 0;
+			simscsi_fillresult(sc, buf, 8);
 			sc->result = GOOD;
 			break;
 
 		      case MODE_SENSE:
 		      case MODE_SENSE_10:
 			/* sd.c uses this to determine whether disk does write-caching. */
-			memset(sc->request_buffer, 0, 128);
+			simscsi_fillresult(sc, (char *)empty_zero_page, sc->request_bufflen);
 			sc->result = GOOD;
 			break;