[SCSI] libsas: Add a sysfs knob to enable/disable a phy

This patch lets a user arbitrarily enable or disable a phy via sysfs.
Potential applications include shutting down a phy to replace one
lane of wide port, and (more importantly) providing a method for the
libata SATL to control the phy.

Signed-off-by: Darrick J. Wong <djwong@us.ibm.com>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>

1 files changed, 51 insertions, 0 deletions

diff --git a/drivers/scsi/scsi_transport_sas.c b/drivers/scsi/scsi_transport_sas.c
index 5c0b75bbfa10..9e38c1894bb2 100644
--- a/drivers/scsi/scsi_transport_sas.c
+++ b/drivers/scsi/scsi_transport_sas.c
@@ -336,6 +336,51 @@ show_sas_device_type(struct class_device *cdev, char *buf)
 }
 static CLASS_DEVICE_ATTR(device_type, S_IRUGO, show_sas_device_type, NULL);
 
+static ssize_t do_sas_phy_enable(struct class_device *cdev,
+                size_t count, int enable)
+{
+        struct sas_phy *phy = transport_class_to_phy(cdev);
+        struct Scsi_Host *shost = dev_to_shost(phy->dev.parent);
+        struct sas_internal *i = to_sas_internal(shost->transportt);
+        int error;
+
+        error = i->f->phy_enable(phy, enable);
+        if (error)
+                return error;
+        phy->enabled = enable;
+        return count;
+};
+
+static ssize_t store_sas_phy_enable(struct class_device *cdev,
+                const char *buf, size_t count)
+{
+        if (count < 1)
+                return -EINVAL;
+
+        switch (buf[0]) {
+        case '0':
+                do_sas_phy_enable(cdev, count, 0);
+                break;
+        case '1':
+                do_sas_phy_enable(cdev, count, 1);
+                break;
+        default:
+                return -EINVAL;
+        }
+
+        return count;
+}
+
+static ssize_t show_sas_phy_enable(struct class_device *cdev, char *buf)
+{
+        struct sas_phy *phy = transport_class_to_phy(cdev);
+
+        return snprintf(buf, 20, "%d", phy->enabled);
+}
+
+static CLASS_DEVICE_ATTR(enable, S_IRUGO | S_IWUSR, show_sas_phy_enable,
+                         store_sas_phy_enable);
+
 static ssize_t do_sas_phy_reset(struct class_device *cdev,
                 size_t count, int hard_reset)
 {
@@ -435,6 +480,7 @@ struct sas_phy *sas_phy_alloc(struct device *parent, int number)
                 return NULL;
 
         phy->number = number;
+        phy->enabled = 1;
 
         device_initialize(&phy->dev);
         phy->dev.parent = get_device(parent);
@@ -1389,6 +1435,10 @@ static int sas_user_scan(struct Scsi_Host *shost, uint channel,
         SETUP_TEMPLATE_RW(phy_attrs, field, S_IRUGO | S_IWUSR, 1,       \
                         !i->f->set_phy_speed, S_IRUGO)
 
+#define SETUP_OPTIONAL_PHY_ATTRIBUTE_RW(field, func)                    \
+        SETUP_TEMPLATE_RW(phy_attrs, field, S_IRUGO | S_IWUSR, 1,       \
+                          !i->f->func, S_IRUGO)
+
 #define SETUP_PORT_ATTRIBUTE(field)                                     \
         SETUP_TEMPLATE(port_attrs, field, S_IRUGO, 1)
 
@@ -1479,6 +1529,7 @@ sas_attach_transport(struct sas_function_template *ft)
         SETUP_PHY_ATTRIBUTE(phy_reset_problem_count);
         SETUP_OPTIONAL_PHY_ATTRIBUTE_WRONLY(link_reset, phy_reset);
         SETUP_OPTIONAL_PHY_ATTRIBUTE_WRONLY(hard_reset, phy_reset);
+        SETUP_OPTIONAL_PHY_ATTRIBUTE_RW(enable, phy_enable);
         i->phy_attrs[count] = NULL;
 
         count = 0;