libata: export ata_port port_no attribute via /sys

While registering host controller track port number based upon number
of ports available on the controller, export port_no attribute through
/sys. This patch is needed by udev for composing persistent links in
/dev/disk/by-path.

/sys/devices/pci0000:00/0000:00:1f.2/ata8/ata_port/ata8
total 0
lrwxrwxrwx. 1 root root    0 Mar  6 12:43 device -> ../../../ata8
-r--r--r--. 1 root root 4096 Mar  6 12:43 idle_irq
-r--r--r--. 1 root root 4096 Mar  6 12:43 nr_pmp_links
-r--r--r--. 1 root root 4096 Mar  6 12:43 port_no
drwxr-xr-x. 2 root root    0 Mar  6 12:42 power
lrwxrwxrwx. 1 root root    0 Mar  6 12:41 subsystem -> ../../../../../../class/ata_port
-rw-r--r--. 1 root root 4096 Mar  6 12:40 uevent
1

Signed-off-by: David Milburn <dmilburn@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

drivers/ata/libata-core.c

@@ -5636,6 +5636,7 @@ struct ata_port *ata_port_alloc(struct ata_host *host)
 	ap->pflags |= ATA_PFLAG_INITIALIZING | ATA_PFLAG_FROZEN;
 	ap->lock = &host->lock;
 	ap->print_id = -1;
+	ap->local_port_no = -1;
 	ap->host = host;
 	ap->dev = host->dev;
 
@@ -6126,9 +6127,10 @@ int ata_host_register(struct ata_host *host, struct scsi_host_template *sht)
 		kfree(host->ports[i]);
 
 	/* give ports names and add SCSI hosts */
-	for (i = 0; i < host->n_ports; i++)
+	for (i = 0; i < host->n_ports; i++) {
 		host->ports[i]->print_id = atomic_inc_return(&ata_print_id);
-
+		host->ports[i]->local_port_no = i + 1;
+	}
 
 	/* Create associated sysfs transport objects  */
 	for (i = 0; i < host->n_ports; i++) {

drivers/ata/libata-transport.c

@@ -37,7 +37,7 @@
 #include "libata.h"
 #include "libata-transport.h"
 
-#define ATA_PORT_ATTRS		2
+#define ATA_PORT_ATTRS		3
 #define ATA_LINK_ATTRS		3
 #define ATA_DEV_ATTRS		9
 
@@ -216,6 +216,7 @@ static DEVICE_ATTR(name, S_IRUGO, show_ata_port_##name, NULL)
 
 ata_port_simple_attr(nr_pmp_links, nr_pmp_links, "%d\n", int);
 ata_port_simple_attr(stats.idle_irq, idle_irq, "%ld\n", unsigned long);
+ata_port_simple_attr(local_port_no, port_no, "%u\n", unsigned int);
 
 static DECLARE_TRANSPORT_CLASS(ata_port_class,
 			       "ata_port", NULL, NULL, NULL);
@@ -709,6 +710,7 @@ struct scsi_transport_template *ata_attach_transport(void)
 	count = 0;
 	SETUP_PORT_ATTRIBUTE(nr_pmp_links);
 	SETUP_PORT_ATTRIBUTE(idle_irq);
+	SETUP_PORT_ATTRIBUTE(port_no);
 	BUG_ON(count > ATA_PORT_ATTRS);
 	i->port_attrs[count] = NULL;
 

include/linux/libata.h

@@ -746,6 +746,7 @@ struct ata_port {
 	/* Flags that change dynamically, protected by ap->lock */
 	unsigned int		pflags; /* ATA_PFLAG_xxx */
 	unsigned int		print_id; /* user visible unique port ID */
+	unsigned int            local_port_no; /* host local port num */
 	unsigned int		port_no; /* 0 based port no. inside the host */
 
 #ifdef CONFIG_ATA_SFF