hwmon: (corsair-psu) add reporting of rail mode via debugfs

Add reporting if the PSU is running in single or multi rail mode via
ocpmode debugfs entry. Also update the documentation and driver comments
accordingly.
Signed-off-by: Wilken Gottwalt <wilken.gottwalt@posteo.net>
Link: https://lore.kernel.org/r/YvS9PZKr0xqFqJny@monster.localdomainSigned-off-by: Guenter Roeck <linux@roeck-us.net>

Documentation/hwmon/corsair-psu.rst

@@ -86,8 +86,9 @@ Debugfs entries
 ---------------
 
 =======================	========================================================
-uptime			Current uptime of the psu
+ocpmode                 Single or multi rail mode of the PCIe power connectors
+product                 Product name of the psu
+uptime			Session uptime of the psu
 uptime_total		Total uptime of the psu
 vendor			Vendor name of the psu
-product			Product name of the psu
 =======================	========================================================

drivers/hwmon/corsair-psu.c

@@ -55,6 +55,7 @@
 #define SECONDS_PER_DAY		(SECONDS_PER_HOUR * 24)
 #define RAIL_COUNT		3 /* 3v3 + 5v + 12v */
 #define TEMP_COUNT		2
+#define OCP_MULTI_RAIL		0x02
 
 #define PSU_CMD_SELECT_RAIL	0x00 /* expects length 2 */
 #define PSU_CMD_RAIL_VOLTS_HCRIT 0x40 /* the rest of the commands expect length 3 */
@@ -71,9 +72,10 @@
 #define PSU_CMD_RAIL_WATTS	0x96
 #define PSU_CMD_VEND_STR	0x99
 #define PSU_CMD_PROD_STR	0x9A
-#define PSU_CMD_TOTAL_WATTS	0xEE
 #define PSU_CMD_TOTAL_UPTIME	0xD1
 #define PSU_CMD_UPTIME		0xD2
+#define PSU_CMD_OCPMODE		0xD8
+#define PSU_CMD_TOTAL_WATTS	0xEE
 #define PSU_CMD_INIT		0xFE
 
 #define L_IN_VOLTS		"v_in"
@@ -268,6 +270,7 @@ static int corsairpsu_get_value(struct corsairpsu_data *priv, u8 cmd, u8 rail, l
 		break;
 	case PSU_CMD_TOTAL_UPTIME:
 	case PSU_CMD_UPTIME:
+	case PSU_CMD_OCPMODE:
 		*val = tmp;
 		break;
 	default:
@@ -660,6 +663,29 @@ static int product_show(struct seq_file *seqf, void *unused)
 }
 DEFINE_SHOW_ATTRIBUTE(product);
 
+static int ocpmode_show(struct seq_file *seqf, void *unused)
+{
+	struct corsairpsu_data *priv = seqf->private;
+	long val;
+	int ret;
+
+	/*
+	 * The rail mode is switchable on the fly. The RAW interface can be used for this. But it
+	 * will not be included here, because I consider it somewhat dangerous for the health of the
+	 * PSU. The returned value can be a bogus one, if the PSU is in the process of switching and
+	 * getting of the value itself can also fail during this. Because of this every other value
+	 * than OCP_MULTI_RAIL can be considered as "single rail".
+	 */
+	ret = corsairpsu_get_value(priv, PSU_CMD_OCPMODE, 0, &val);
+	if (ret < 0)
+		seq_puts(seqf, "N/A\n");
+	else
+		seq_printf(seqf, "%s\n", (val == OCP_MULTI_RAIL) ? "multi rail" : "single rail");
+
+	return 0;
+}
+DEFINE_SHOW_ATTRIBUTE(ocpmode);
+
 static void corsairpsu_debugfs_init(struct corsairpsu_data *priv)
 {
 	char name[32];
@@ -671,6 +697,7 @@ static void corsairpsu_debugfs_init(struct corsairpsu_data *priv)
 	debugfs_create_file("uptime_total", 0444, priv->debugfs, priv, &uptime_total_fops);
 	debugfs_create_file("vendor", 0444, priv->debugfs, priv, &vendor_fops);
 	debugfs_create_file("product", 0444, priv->debugfs, priv, &product_fops);
+	debugfs_create_file("ocpmode", 0444, priv->debugfs, priv, &ocpmode_fops);
 }
 
 #else