[PATCH] 5/6: scsi_inq_timeout

[Kurt Garloff <garloff@suse.de>]

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Feature.

Introduce a new SCSI scanning boot/module parameter
scsi_inq_timeout=N
which sets the timeout used when the INQUIRY is send in the SCSI 
scanning procedure to N seconds. (Half a second is added, so 0 is safe.)
This is useful, because some devices need an excessive amount of time to 
recover from the bootup SCSI reset.
Also changes the default for PPC64, as some largely used crap chip there
requires it.

Note that the second INQUIRY (with more than 36 bytes) only gets half 
the amount of seconds, the long delay for the first is only due to the 
recovery needed from the initial bus reset.

--- linux-2.6.5.noreplunhost/drivers/scsi/scsi_scan.c.orig	2004-04-15 22:51:08.000000000 +0200
+++ linux-2.6.5.noreplunhost/drivers/scsi/scsi_scan.c	2004-04-16 19:30:43.289826746 +0200
@@ -125,6 +125,22 @@ MODULE_PARM_DESC(scsi_allow_ghost_device
 		 "allow devices marked as being offline to be accessed anyway "
 		 "(0 = off, else allow ghosts on lun 0 through allow_ghost_devices - 1");
 
+/* Some AChip ARC765 based DVD-ROM's take 15 or more seconds
+ * to reset.  A scan will fail if made right after a reset.
+ * It's completely broken device behaviour: SCSI specification
+ * says devices need to be able to respond to INQUIRY always
+ * (after a selection timeout ... of 250ms).
+ */
+#ifdef __powerpc64__
+static unsigned int scsi_inq_timeout = SCSI_TIMEOUT/HZ+25;
+#else
+static unsigned int scsi_inq_timeout = SCSI_TIMEOUT/HZ+3;
+#endif
+
+module_param_named(scsi_inq_timeout, scsi_inq_timeout, int, S_IRUGO|S_IWUSR);
+MODULE_PARM_DESC(scsi_inq_timeout, 
+		 "Timeout (in seconds) waiting for devices to answer INQUIRY."
+		 " Default is 6. Some non-compliant devices need more.");
 
 /**
  * scsi_unlock_floptical - unlock device via a special MODE SENSE command
@@ -376,7 +392,7 @@ static void scsi_probe_lun(struct scsi_r
 
 	memset(inq_result, 0, 36);
 	scsi_wait_req(sreq, (void *) scsi_cmd, (void *) inq_result, 36,
-		      SCSI_TIMEOUT + 4 * HZ, 3);
+		      HZ/2 + HZ*scsi_inq_timeout, 3);
 
 	SCSI_LOG_SCAN_BUS(3, printk(KERN_INFO "scsi scan: 1st INQUIRY %s with"
 			" code 0x%x\n", sreq->sr_result ?
@@ -425,7 +441,7 @@ static void scsi_probe_lun(struct scsi_r
 		memset(inq_result, 0, possible_inq_resp_len);
 		scsi_wait_req(sreq, (void *) scsi_cmd,
 			      (void *) inq_result,
-			      possible_inq_resp_len, SCSI_TIMEOUT + 4 * HZ, 3);
+			      possible_inq_resp_len, (1+scsi_inq_timeout)*(HZ/2), 3);
 		SCSI_LOG_SCAN_BUS(3, printk(KERN_INFO "scsi scan: 2nd INQUIRY"
 				" %s with code 0x%x\n", sreq->sr_result ?
 				"failed" : "successful", sreq->sr_result));
-- 
Kurt Garloff  <garloff@suse.de>                            Cologne, DE 
SUSE LINUX AG, Nuernberg, DE                          SUSE Labs (Head)

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