> To Do
> -----
> Linux sends a 1K buffer with SCSI inquiries. The ANSI-SCSI limit is 255.
I don't see how this can be. In scan_scsis() scsi_result0[256] is
declared, and if that isn't appropriate for host needing DMA then
we kmalloc(512, GFP_DMA) - either way it doesn't matter since the
allocation length field in the CCB for INQUIRY is only a byte (and
we set it to 255). Even scsi_wait_req() is told the the result buffer
length is 255 when the INQUIRY command is lodged.
> Linux uses TEST_UNIT_READY to chck for device presence on a PUN/LUN. The
> INQUIRY is the only valid test allowed by the spec.
The draft of SCSI-2 spec I have here hints that INQUIRY should be used
to probe system configuration and that TEST_UNIT_READY is more for
polling on devices with removable media. I tossed the TEST_UNIT_READY
part out and INQUIRY alone works fine (one disk, 2 CDs and a tape on
a BusLogic clone - all found as per usual).
Paul.
--- 2400-test1/linux/drivers/scsi/scsi_scan.c~ Fri May 26 16:34:59 2000
+++ 2400-test1/linux/drivers/scsi/scsi_scan.c Sat May 27 06:14:44 2000
@@ -499,39 +499,14 @@
SDpnt->expecting_cc_ua = 0;
SDpnt->starved = 0;
- scsi_cmd[0] = TEST_UNIT_READY;
- scsi_cmd[1] = lun << 5;
- scsi_cmd[2] = scsi_cmd[3] = scsi_cmd[4] = scsi_cmd[5] = 0;
-
SRpnt = scsi_allocate_request(SDpnt);
- SRpnt->sr_data_direction = SCSI_DATA_NONE;
-
- scsi_wait_req (SRpnt, (void *) scsi_cmd,
- (void *) NULL,
- 0, SCSI_TIMEOUT + 4 * HZ, 5);
-
- SCSI_LOG_SCAN_BUS(3, printk("scsi: scan_scsis_single id %d lun %d. Return code
0x%08x\n",
- dev, lun, SRpnt->sr_result));
- SCSI_LOG_SCAN_BUS(3, print_driverbyte(SRpnt->sr_result));
- SCSI_LOG_SCAN_BUS(3, print_hostbyte(SRpnt->sr_result));
- SCSI_LOG_SCAN_BUS(3, printk("\n"));
+ /*
+ * We used to do a TEST_UNIT_READY before the INQUIRY but that was
+ * not really necessary. Spec recommends using INQUIRY to scan for
+ * devices (and TEST_UNIT_READY to poll for media change). - Paul G.
+ */
- if (SRpnt->sr_result) {
- if (((driver_byte(SRpnt->sr_result) & DRIVER_SENSE) ||
- (status_byte(SRpnt->sr_result) & CHECK_CONDITION)) &&
- ((SRpnt->sr_sense_buffer[0] & 0x70) >> 4) == 7) {
- if (((SRpnt->sr_sense_buffer[2] & 0xf) != NOT_READY) &&
- ((SRpnt->sr_sense_buffer[2] & 0xf) != UNIT_ATTENTION) &&
- ((SRpnt->sr_sense_buffer[2] & 0xf) != ILLEGAL_REQUEST ||
lun > 0)) {
- scsi_release_request(SRpnt);
- return 1;
- }
- } else {
- scsi_release_request(SRpnt);
- return 0;
- }
- }
SCSI_LOG_SCAN_BUS(3, printk("scsi: performing INQUIRY\n"));
/*
* Build an INQUIRY command block.
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