[dm-devel] [PATCH] scsi_dh_rdac: Add empty set_params function to scsi_dh_rdac

[Moger, Babu]

This patch adds empty set_params function to scsi_dh_rdac.

This patch is required for the following features to work properly.
1. add  retain_attached_hw_handler feature

http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=commit;h=a58a935d5a1b2ad267017a68c3a1bca26226cc76

2. add scsi_dh_attached_handler_name

http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=commit;h=7e8a74b177f17d100916b6ad415450f7c9508691


DM layer detaches the handler if the set_params is not implemented or fails.

For example if we pass following parameters from multipath:

	features "1 retain_attached_hw_handler" (consider rdac as attached_hw_handler)
	hardware_handler "2 alua 1"

If the attached_hw_handler is rdac, then DM anyway tries to call set_params on rdac. Because rdac does not 
implement set_params, scsi_dh_set_params fails and DM detaches the handler.

This patch fixes this problem. 

Signed-off-by: Babu Moger <babu.moger at netapp.com>
---
--- linux-3.5-rc7/drivers/scsi/device_handler/scsi_dh_rdac.c.orig	2012-08-08 10:38:54.000000000 -0500
+++ linux-3.5-rc7/drivers/scsi/device_handler/scsi_dh_rdac.c	2012-08-08 11:02:10.000000000 -0500
@@ -816,6 +816,17 @@ static const struct scsi_dh_devlist rdac
 	{NULL, NULL},
 };
 
+/*
+ * params - parameters in the following format
+ *      "no_of_params\0param1\0param2\0param3\0...\0"
+ *      for example, string for 2 parameters with value 10 and 21
+ *      is specified as "2\010\021\0".
+ */
+static int rdac_set_params(struct scsi_device *sdev, const char *params)
+{
+	return 0;
+}
+
 static bool rdac_match(struct scsi_device *sdev)
 {
 	int i;
@@ -846,6 +857,7 @@ static struct scsi_device_handler rdac_d
 	.attach = rdac_bus_attach,
 	.detach = rdac_bus_detach,
 	.activate = rdac_activate,
+	.set_params = rdac_set_params,
 	.match = rdac_match,
 };