+/**
+ * sas_tlr_supported - checking TLR bit in vpd 0x90
+ * @sdev: scsi device struct
+ *
+ * Check Transport Layer Retries are supported or not.
+ * If vpd page 0x90 is present, TRL is supported.
+ *
+ */
+unsigned int
+sas_tlr_supported(struct scsi_device *sdev)
+{
+ const int vpd_len = 32;
+ struct sas_end_device *rdev = sas_sdev_to_rdev(sdev);
+ char *buffer = kzalloc(vpd_len, GFP_KERNEL);
+ int ret = 0;
+
+ if (scsi_get_vpd_page(sdev, 0x90, buffer, vpd_len))
+ goto out;
+
+ /*
+ * Magic numbers: the VPD Protocol page (0x90)
+ * has a 4 byte header and then one entry per device port
+ * the TLR bit is at offset 8 on each port entry
+ * if we take the first port, that's at total offset 12
+ */
+ ret = buffer[12] & 0x01;
+
+ out:
+ kfree(buffer);
+ rdev->tlr_supported = ret;
+ return ret;
+
+}
+EXPORT_SYMBOL_GPL(sas_tlr_supported);
+
+/**
+ * sas_disable_tlr - setting TLR flags
+ * @sdev: scsi device struct
+ *
+ * Seting tlr_enabled flag to 0.
+ *
+ */
+void
+sas_disable_tlr(struct scsi_device *sdev)
+{
+ struct sas_end_device *rdev = sas_sdev_to_rdev(sdev);
+
+ rdev->tlr_enabled = 0;
+}
+EXPORT_SYMBOL_GPL(sas_disable_tlr);
+
+/**
+ * sas_enable_tlr - setting TLR flags
+ * @sdev: scsi device struct
+ *
+ * Seting tlr_enabled flag 1.
+ *
+ */
+void sas_enable_tlr(struct scsi_device *sdev)
+{
+ unsigned int tlr_supported = 0;
+ tlr_supported = sas_tlr_supported(sdev);
+
+ if (tlr_supported) {
+ struct sas_end_device *rdev = sas_sdev_to_rdev(sdev);
+
+ rdev->tlr_enabled = 1;
+ }
+
+ return;
+}
+EXPORT_SYMBOL_GPL(sas_enable_tlr);
+
+unsigned int sas_is_tlr_enabled(struct scsi_device *sdev)
+{
+ struct sas_end_device *rdev = sas_sdev_to_rdev(sdev);
+ return rdev->tlr_enabled;
+}
+EXPORT_SYMBOL_GPL(sas_is_tlr_enabled);