Re: [PATCH 1/1] scsi: storvsc: Support manual scan of FC hosts on Hyper-V

[James Bottomley <James.Bottomley@HansenPartnership.com>]

On Thu, 2016-03-17 at 00:01 +0000, KY Srinivasan wrote:
> The only attributes I would be interested are:
> 1) node name
> 2) port name
> 
> Ideally, if this can show under /sys/class/fc_host/hostx/port_name
> and node_name,
> it will be ideal since all user scripts can work.

OK, like this?

>From 7af7c428e7e04ddcc87fda12d6571e3dff8ae024 Mon Sep 17 00:00:00 2001
From: James Bottomley <James.Bottomley@HansenPartnership.com>
Date: Fri, 18 Mar 2016 15:35:45 -0700
Subject: scsi_transport_fc: introduce lightweight class for virtualization
 systems

The FC transport class is very heavily tilted towards helping things
which operate a fabric (as it should be).  However, there seems to be
a need for a lightweight version for use in virtual systems that
simply want to show pass through FC information without making any use
of the heavyweight functions.  This is an attempt to give them what
they want: the lightweight class has no vports or rports and only two
host attributes.  Essentially, it's designed for the HV storvsc
driver, but if other virtualizataion systems have similar problems, we
can add more attributes.

Signed-off-by: James Bottomley <jejb@linux.vnet.ibm.com>
---
 drivers/scsi/scsi_transport_fc.c | 94 ++++++++++++++++++++++++++++++++++++++++
 include/scsi/scsi_transport_fc.h |  3 ++
 2 files changed, 97 insertions(+)

diff --git a/drivers/scsi/scsi_transport_fc.c b/drivers/scsi/scsi_transport_fc.c
index 8a88226..a9fcb4d 100644
--- a/drivers/scsi/scsi_transport_fc.c
+++ b/drivers/scsi/scsi_transport_fc.c
@@ -351,6 +351,27 @@ struct fc_internal {
 
 #define to_fc_internal(tmpl)	container_of(tmpl, struct fc_internal, t)
 
+#define FC_LW_HOST_NUM_ATTRS 	2
+struct fc_lw_internal {
+	struct scsi_transport_template t;
+	struct fc_function_template *f;
+
+	/*
+	 * For attributes : each object has :
+	 *   An array of the actual attributes structures
+	 *   An array of null-terminated pointers to the attribute
+	 *     structures - used for mid-layer interaction.
+	 *
+	 * The attribute containers for the starget and host are are
+	 * part of the midlayer. As the remote port is specific to the
+	 * fc transport, we must provide the attribute container.
+	 */
+	struct device_attribute private_host_attrs[FC_LW_HOST_NUM_ATTRS];
+	struct device_attribute *host_attrs[FC_LW_HOST_NUM_ATTRS + 1];
+};
+
+#define to_fc_lw_internal(tmpl)	container_of(tmpl, struct fc_lw_internal, t)
+
 static int fc_target_setup(struct transport_container *tc, struct device *dev,
 			   struct device *cdev)
 {
@@ -472,6 +493,12 @@ static int fc_host_remove(struct transport_container *tc, struct device *dev,
 	return 0;
 }
 
+static DECLARE_TRANSPORT_CLASS(fc_lw_host_class,
+			       "fc_host",
+			       NULL,
+			       NULL,
+			       NULL);
+
 static DECLARE_TRANSPORT_CLASS(fc_host_class,
 			       "fc_host",
 			       fc_host_setup,
@@ -1968,6 +1995,25 @@ static int fc_host_match(struct attribute_container *cont,
 	return &i->t.host_attrs.ac == cont;
 }
 
+static int fc_lw_host_match(struct attribute_container *cont,
+			  struct device *dev)
+{
+	struct Scsi_Host *shost;
+	struct fc_lw_internal *i;
+
+	if (!scsi_is_host_device(dev))
+		return 0;
+
+	shost = dev_to_shost(dev);
+	if (!shost->transportt  || shost->transportt->host_attrs.ac.class
+	    != &fc_lw_host_class.class)
+		return 0;
+
+	i = to_fc_lw_internal(shost->transportt);
+
+	return &i->t.host_attrs.ac == cont;
+}
+
 static int fc_target_match(struct attribute_container *cont,
 			    struct device *dev)
 {
@@ -2171,6 +2217,54 @@ static int fc_it_nexus_response(struct Scsi_Host *shost, u64 nexus, int result)
 	return i->f->it_nexus_response(shost, nexus, result);
 }
 
+/**
+ * fc_attach_lw_transport - light weight attach function
+ * @ft:		function template for optional attributes
+ *
+ * This attach function is to be used only for virtual FC emulators
+ * which do not have a physical fabric underneath them and thus only
+ * need a few attributes and no helper functions
+ */
+struct scsi_transport_template *
+fc_lw_attach_transport(struct fc_function_template *ft)
+{
+	int count;
+	struct fc_lw_internal *i = kzalloc(sizeof(struct fc_lw_internal),
+					   GFP_KERNEL);
+
+	if (unlikely(!i))
+		return NULL;
+
+	i->t.host_attrs.ac.attrs = &i->host_attrs[0];
+	i->t.host_attrs.ac.class = &fc_lw_host_class.class;
+	i->t.host_attrs.ac.match = fc_lw_host_match;
+	i->t.host_size = sizeof(struct fc_host_attrs);
+	transport_container_register(&i->t.host_attrs);
+
+	i->f = ft;
+
+	count = 0;
+	SETUP_HOST_ATTRIBUTE_RD(node_name);
+	SETUP_HOST_ATTRIBUTE_RD(port_name);
+
+	BUG_ON(count > FC_HOST_NUM_ATTRS);
+
+	i->host_attrs[count] = NULL;
+
+	return &i->t;
+}
+EXPORT_SYMBOL(fc_lw_attach_transport);
+
+void fc_lw_release_transport(struct scsi_transport_template *t)
+{
+	struct fc_lw_internal *i = to_fc_lw_internal(t);
+
+	transport_container_unregister(&i->t.host_attrs);
+
+	kfree(i);
+}
+EXPORT_SYMBOL(fc_lw_release_transport);
+
 struct scsi_transport_template *
 fc_attach_transport(struct fc_function_template *ft)
 {
diff --git a/include/scsi/scsi_transport_fc.h b/include/scsi/scsi_transport_fc.h
index 784bc2c..b0a9a64 100644
--- a/include/scsi/scsi_transport_fc.h
+++ b/include/scsi/scsi_transport_fc.h
@@ -835,6 +835,9 @@ fc_vport_set_state(struct fc_vport *vport, enum fc_vport_state new_state)
 	vport->vport_state = new_state;
 }
 
+struct scsi_transport_template *fc_lw_attach_transport(
+			struct fc_function_template *);
+void fc_lw_release_transport(struct scsi_transport_template *);
 struct scsi_transport_template *fc_attach_transport(
 			struct fc_function_template *);
 void fc_release_transport(struct scsi_transport_template *);
-- 
2.6.2