ACPI: ibm-acpi: clean up fan_read

This patch cleans up fan_read so that it is much easier to read and
extend.

The patch fixes the userspace ABI to return "status: not supported" (like
all other ibm-acpi functions) when neither fan status or fan control are
possible.

It also fixes the userspace ABI to return EIO if ACPI access to the EC
fails, instead of returning "status: unreadable" or "speed: unreadable".
Signed-off-by: NHenrique de Moraes Holschuh <hmh@hmh.eng.br>

drivers/acpi/ibm_acpi.c

@@ -1741,40 +1741,48 @@ static int fan_init(void)
 static int fan_read(char *p)
 {
 	int len = 0;
-	int s;
 	u8 lo, hi, status;
 
-	if (gfan_handle) {
+	switch (fan_status_access_mode) {
+	case IBMACPI_FAN_RD_ACPI_GFAN:
 		/* 570, 600e/x, 770e, 770x */
-		if (!acpi_evalf(gfan_handle, &s, NULL, "d"))
+		if (unlikely(!acpi_evalf(gfan_handle, &status, NULL, "d")))
 			return -EIO;
 
-		len += sprintf(p + len, "level:\t\t%d\n", s);
-	} else {
+		len += sprintf(p + len, "level:\t\t%d\n", status);
+
+		break;
+
+	case IBMACPI_FAN_RD_TPEC:
 		/* all except 570, 600e/x, 770e, 770x */
-		if (!acpi_ec_read(fan_status_offset, &status))
-			len += sprintf(p + len, "status:\t\tunreadable\n");
+		if (unlikely(!acpi_ec_read(fan_status_offset, &status)))
+			return -EIO;
 		else
 			len += sprintf(p + len, "status:\t\t%s\n",
 				       enabled(status, 7));
 
-		if (!acpi_ec_read(fan_rpm_offset, &lo) ||
-		    !acpi_ec_read(fan_rpm_offset + 1, &hi))
-			len += sprintf(p + len, "speed:\t\tunreadable\n");
+		if (unlikely(!acpi_ec_read(fan_rpm_offset, &lo) ||
+			     !acpi_ec_read(fan_rpm_offset + 1, &hi)))
+			return -EIO;
 		else
 			len += sprintf(p + len, "speed:\t\t%d\n",
 				       (hi << 8) + lo);
+
+		break;
+
+	case IBMACPI_FAN_NONE:
+	default:
+		len += sprintf(p + len, "status:\t\tnot supported\n");
 	}
 
-	if (sfan_handle)
-		/* 570, 770x-JL */
+	if (fan_control_commands & IBMACPI_FAN_CMD_LEVEL)
 		len += sprintf(p + len, "commands:\tlevel <level>"
 			       " (<level> is 0-7)\n");
-	if (!gfan_handle)
-		/* all except 570, 600e/x, 770e, 770x */
+
+	if (fan_control_commands & IBMACPI_FAN_CMD_ENABLE)
 		len += sprintf(p + len, "commands:\tenable, disable\n");
-	if (fans_handle)
-		/* X31, X40 */
+
+	if (fan_control_commands & IBMACPI_FAN_CMD_SPEED)
 		len += sprintf(p + len, "commands:\tspeed <speed>"
 			       " (<speed> is 0-65535)\n");