edac: only create sdram_scrub_rate where supported

Currently, sdram_scrub_rate sysfs node is created even if the device
doesn't support get/set the scub rate. Change the logic to only
create this device node when the operation is supported.

Reported-by: Felipe Balbi <balbi@ti.com>
Acked-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/edac/edac_mc_sysfs.c

@@ -7,7 +7,7 @@
  *
  * Written Doug Thompson <norsk5@xmission.com> www.softwarebitmaker.com
  *
- * (c) 2012 - Mauro Carvalho Chehab <mchehab@redhat.com>
+ * (c) 2012-2013 - Mauro Carvalho Chehab <mchehab@redhat.com>
  *	The entire API were re-written, and ported to use struct device
  *
  */
@@ -677,9 +677,6 @@ static ssize_t mci_sdram_scrub_rate_store(struct device *dev,
 	unsigned long bandwidth = 0;
 	int new_bw = 0;
 
-	if (!mci->set_sdram_scrub_rate)
-		return -ENODEV;
-
 	if (strict_strtoul(data, 10, &bandwidth) < 0)
 		return -EINVAL;
 
@@ -703,9 +700,6 @@ static ssize_t mci_sdram_scrub_rate_show(struct device *dev,
 	struct mem_ctl_info *mci = to_mci(dev);
 	int bandwidth = 0;
 
-	if (!mci->get_sdram_scrub_rate)
-		return -ENODEV;
-
 	bandwidth = mci->get_sdram_scrub_rate(mci);
 	if (bandwidth < 0) {
 		edac_printk(KERN_DEBUG, EDAC_MC, "Error reading scrub rate\n");
@@ -866,8 +860,7 @@ DEVICE_ATTR(ce_count, S_IRUGO, mci_ce_count_show, NULL);
 DEVICE_ATTR(max_location, S_IRUGO, mci_max_location_show, NULL);
 
 /* memory scrubber attribute file */
-DEVICE_ATTR(sdram_scrub_rate, S_IRUGO | S_IWUSR, mci_sdram_scrub_rate_show,
-	mci_sdram_scrub_rate_store);
+DEVICE_ATTR(sdram_scrub_rate, 0, NULL, NULL);
 
 static struct attribute *mci_attrs[] = {
 	&dev_attr_reset_counters.attr,
@@ -878,7 +871,6 @@ static struct attribute *mci_attrs[] = {
 	&dev_attr_ce_noinfo_count.attr,
 	&dev_attr_ue_count.attr,
 	&dev_attr_ce_count.attr,
-	&dev_attr_sdram_scrub_rate.attr,
 	&dev_attr_max_location.attr,
 	NULL
 };
@@ -1012,6 +1004,22 @@ int edac_create_sysfs_mci_device(struct mem_ctl_info *mci)
 		return err;
 	}
 
+	if (mci->set_sdram_scrub_rate || mci->get_sdram_scrub_rate) {
+		if (mci->get_sdram_scrub_rate) {
+			dev_attr_sdram_scrub_rate.attr.mode |= S_IRUGO;
+			dev_attr_sdram_scrub_rate.show = &mci_sdram_scrub_rate_show;
+		}
+		if (mci->set_sdram_scrub_rate) {
+			dev_attr_sdram_scrub_rate.attr.mode |= S_IWUSR;
+			dev_attr_sdram_scrub_rate.store = &mci_sdram_scrub_rate_store;
+		}
+		err = device_create_file(&mci->dev,
+					 &dev_attr_sdram_scrub_rate);
+		if (err) {
+			edac_dbg(1, "failure: create sdram_scrub_rate\n");
+			goto fail2;
+		}
+	}
 	/*
 	 * Create the dimm/rank devices
 	 */
@@ -1056,6 +1064,7 @@ int edac_create_sysfs_mci_device(struct mem_ctl_info *mci)
 			continue;
 		device_unregister(&dimm->dev);
 	}
+fail2:
 	device_unregister(&mci->dev);
 	bus_unregister(&mci->bus);
 	kfree(mci->bus.name);